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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/ceph/ceph_debug.h>
 
 #include <linux/fs.h>
 #include <linux/wait.h>
 #include <linux/slab.h>
 #include <linux/gfp.h>
 #include <linux/sched.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/ratelimit.h>
 #include <linux/bits.h>
 #include <linux/ktime.h>
 #include <linux/bitmap.h>
 
 #include "super.h"
 #include "mds_client.h"
 
 #include <linux/ceph/ceph_features.h>
 #include <linux/ceph/messenger.h>
 #include <linux/ceph/decode.h>
 #include <linux/ceph/pagelist.h>
 #include <linux/ceph/auth.h>
 #include <linux/ceph/debugfs.h>
 
 #define RECONNECT_MAX_SIZE (INT_MAX - PAGE_SIZE)
 
 /*
  * A cluster of MDS (metadata server) daemons is responsible for
  * managing the file system namespace (the directory hierarchy and
  * inodes) and for coordinating shared access to storage.  Metadata is
  * partitioning hierarchically across a number of servers, and that
  * partition varies over time as the cluster adjusts the distribution
  * in order to balance load.
  *
  * The MDS client is primarily responsible to managing synchronous
  * metadata requests for operations like open, unlink, and so forth.
  * If there is a MDS failure, we find out about it when we (possibly
  * request and) receive a new MDS map, and can resubmit affected
  * requests.
  *
  * For the most part, though, we take advantage of a lossless
  * communications channel to the MDS, and do not need to worry about
  * timing out or resubmitting requests.
  *
  * We maintain a stateful "session" with each MDS we interact with.
  * Within each session, we sent periodic heartbeat messages to ensure
  * any capabilities or leases we have been issues remain valid.  If
  * the session times out and goes stale, our leases and capabilities
  * are no longer valid.
  */
 
 struct ceph_reconnect_state {
     struct ceph_mds_session *session;
     int nr_caps, nr_realms;
     struct ceph_pagelist *pagelist;
     unsigned msg_version;
     bool allow_multi;
 };
 
 static void __wake_requests(struct ceph_mds_client *mdsc,
                 struct list_head *head);
 static void ceph_cap_release_work(struct work_struct *work);
 static void ceph_cap_reclaim_work(struct work_struct *work);
 
 static const struct ceph_connection_operations mds_con_ops;
 
 
 /*
  * mds reply parsing
  */
 
 static int parse_reply_info_quota(void **p, void *end,
                   struct ceph_mds_reply_info_in *info)
 {
     u8 struct_v, struct_compat;
     u32 struct_len;
 
     ceph_decode_8_safe(p, end, struct_v, bad);
     ceph_decode_8_safe(p, end, struct_compat, bad);
     /* struct_v is expected to be >= 1. we only
      * understand encoding with struct_compat == 1. */
     if (!struct_v || struct_compat != 1)
         goto bad;
     ceph_decode_32_safe(p, end, struct_len, bad);
     ceph_decode_need(p, end, struct_len, bad);
     end = *p + struct_len;
     ceph_decode_64_safe(p, end, info->max_bytes, bad);
     ceph_decode_64_safe(p, end, info->max_files, bad);
     *p = end;
     return 0;
 bad:
     return -EIO;
 }
 
 /*
  * parse individual inode info
  */
 static int parse_reply_info_in(void **p, void *end,
                    struct ceph_mds_reply_info_in *info,
                    u64 features)
 {
     int err = 0;
     u8 struct_v = 0;
 
     if (features == (u64)-1) {
         u32 struct_len;
         u8 struct_compat;
         ceph_decode_8_safe(p, end, struct_v, bad);
         ceph_decode_8_safe(p, end, struct_compat, bad);
         /* struct_v is expected to be >= 1. we only understand
          * encoding with struct_compat == 1. */
         if (!struct_v || struct_compat != 1)
             goto bad;
         ceph_decode_32_safe(p, end, struct_len, bad);
         ceph_decode_need(p, end, struct_len, bad);
         end = *p + struct_len;
     }
 
     ceph_decode_need(p, end, sizeof(struct ceph_mds_reply_inode), bad);
     info->in = *p;
     *p += sizeof(struct ceph_mds_reply_inode) +
         sizeof(*info->in->fragtree.splits) *
         le32_to_cpu(info->in->fragtree.nsplits);
 
     ceph_decode_32_safe(p, end, info->symlink_len, bad);
     ceph_decode_need(p, end, info->symlink_len, bad);
     info->symlink = *p;
     *p += info->symlink_len;
 
     ceph_decode_copy_safe(p, end, &info->dir_layout,
                   sizeof(info->dir_layout), bad);
     ceph_decode_32_safe(p, end, info->xattr_len, bad);
     ceph_decode_need(p, end, info->xattr_len, bad);
     info->xattr_data = *p;
     *p += info->xattr_len;
 
     if (features == (u64)-1) {
         /* inline data */
         ceph_decode_64_safe(p, end, info->inline_version, bad);
         ceph_decode_32_safe(p, end, info->inline_len, bad);
         ceph_decode_need(p, end, info->inline_len, bad);
         info->inline_data = *p;
         *p += info->inline_len;
         /* quota */
         err = parse_reply_info_quota(p, end, info);
         if (err < 0)
             goto out_bad;
         /* pool namespace */
         ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
         if (info->pool_ns_len > 0) {
             ceph_decode_need(p, end, info->pool_ns_len, bad);
             info->pool_ns_data = *p;
             *p += info->pool_ns_len;
         }
 
         /* btime */
         ceph_decode_need(p, end, sizeof(info->btime), bad);
         ceph_decode_copy(p, &info->btime, sizeof(info->btime));
 
         /* change attribute */
         ceph_decode_64_safe(p, end, info->change_attr, bad);
 
         /* dir pin */
         if (struct_v >= 2) {
             ceph_decode_32_safe(p, end, info->dir_pin, bad);
         } else {
             info->dir_pin = -ENODATA;
         }
 
         /* snapshot birth time, remains zero for v<=2 */
         if (struct_v >= 3) {
             ceph_decode_need(p, end, sizeof(info->snap_btime), bad);
             ceph_decode_copy(p, &info->snap_btime,
                      sizeof(info->snap_btime));
         } else {
             memset(&info->snap_btime, 0, sizeof(info->snap_btime));
         }
 
         /* snapshot count, remains zero for v<=3 */
         if (struct_v >= 4) {
             ceph_decode_64_safe(p, end, info->rsnaps, bad);
         } else {
             info->rsnaps = 0;
         }
 
         *p = end;
     } else {
         if (features & CEPH_FEATURE_MDS_INLINE_DATA) {
             ceph_decode_64_safe(p, end, info->inline_version, bad);
             ceph_decode_32_safe(p, end, info->inline_len, bad);
             ceph_decode_need(p, end, info->inline_len, bad);
             info->inline_data = *p;
             *p += info->inline_len;
         } else
             info->inline_version = CEPH_INLINE_NONE;
 
         if (features & CEPH_FEATURE_MDS_QUOTA) {
             err = parse_reply_info_quota(p, end, info);
             if (err < 0)
                 goto out_bad;
         } else {
             info->max_bytes = 0;
             info->max_files = 0;
         }
 
         info->pool_ns_len = 0;
         info->pool_ns_data = NULL;
         if (features & CEPH_FEATURE_FS_FILE_LAYOUT_V2) {
             ceph_decode_32_safe(p, end, info->pool_ns_len, bad);
             if (info->pool_ns_len > 0) {
                 ceph_decode_need(p, end, info->pool_ns_len, bad);
                 info->pool_ns_data = *p;
                 *p += info->pool_ns_len;
             }
         }
 
         if (features & CEPH_FEATURE_FS_BTIME) {
             ceph_decode_need(p, end, sizeof(info->btime), bad);
             ceph_decode_copy(p, &info->btime, sizeof(info->btime));
             ceph_decode_64_safe(p, end, info->change_attr, bad);
         }
 
         info->dir_pin = -ENODATA;
         /* info->snap_btime and info->rsnaps remain zero */
     }
     return 0;
 bad:
     err = -EIO;
 out_bad:
     return err;
 }
 
 static int parse_reply_info_dir(void **p, void *end,
                 struct ceph_mds_reply_dirfrag **dirfrag,
                 u64 features)
 {
     if (features == (u64)-1) {
         u8 struct_v, struct_compat;
         u32 struct_len;
         ceph_decode_8_safe(p, end, struct_v, bad);
         ceph_decode_8_safe(p, end, struct_compat, bad);
         /* struct_v is expected to be >= 1. we only understand
          * encoding whose struct_compat == 1. */
         if (!struct_v || struct_compat != 1)
             goto bad;
         ceph_decode_32_safe(p, end, struct_len, bad);
         ceph_decode_need(p, end, struct_len, bad);
         end = *p + struct_len;
     }
 
     ceph_decode_need(p, end, sizeof(**dirfrag), bad);
     *dirfrag = *p;
     *p += sizeof(**dirfrag) + sizeof(u32) * le32_to_cpu((*dirfrag)->ndist);
     if (unlikely(*p > end))
         goto bad;
     if (features == (u64)-1)
         *p = end;
     return 0;
 bad:
     return -EIO;
 }
 
 static int parse_reply_info_lease(void **p, void *end,
                   struct ceph_mds_reply_lease **lease,
                   u64 features)
 {
     if (features == (u64)-1) {
         u8 struct_v, struct_compat;
         u32 struct_len;
         ceph_decode_8_safe(p, end, struct_v, bad);
         ceph_decode_8_safe(p, end, struct_compat, bad);
         /* struct_v is expected to be >= 1. we only understand
          * encoding whose struct_compat == 1. */
         if (!struct_v || struct_compat != 1)
             goto bad;
         ceph_decode_32_safe(p, end, struct_len, bad);
         ceph_decode_need(p, end, struct_len, bad);
         end = *p + struct_len;
     }
 
     ceph_decode_need(p, end, sizeof(**lease), bad);
     *lease = *p;
     *p += sizeof(**lease);
     if (features == (u64)-1)
         *p = end;
     return 0;
 bad:
     return -EIO;
 }
 
 /*
  * parse a normal reply, which may contain a (dir+)dentry and/or a
  * target inode.
  */
 static int parse_reply_info_trace(void **p, void *end,
                   struct ceph_mds_reply_info_parsed *info,
                   u64 features)
 {
     int err;
 
     if (info->head->is_dentry) {
         err = parse_reply_info_in(p, end, &info->diri, features);
         if (err < 0)
             goto out_bad;
 
         err = parse_reply_info_dir(p, end, &info->dirfrag, features);
         if (err < 0)
             goto out_bad;
 
         ceph_decode_32_safe(p, end, info->dname_len, bad);
         ceph_decode_need(p, end, info->dname_len, bad);
         info->dname = *p;
         *p += info->dname_len;
 
         err = parse_reply_info_lease(p, end, &info->dlease, features);
         if (err < 0)
             goto out_bad;
     }
 
     if (info->head->is_target) {
         err = parse_reply_info_in(p, end, &info->targeti, features);
         if (err < 0)
             goto out_bad;
     }
 
     if (unlikely(*p != end))
         goto bad;
     return 0;
 
 bad:
     err = -EIO;
 out_bad:
     pr_err("problem parsing mds trace %d\n", err);
     return err;
 }
 
 /*
  * parse readdir results
  */
 static int parse_reply_info_readdir(void **p, void *end,
                 struct ceph_mds_reply_info_parsed *info,
                 u64 features)
 {
     u32 num, i = 0;
     int err;
 
     err = parse_reply_info_dir(p, end, &info->dir_dir, features);
     if (err < 0)
         goto out_bad;
 
     ceph_decode_need(p, end, sizeof(num) + 2, bad);
     num = ceph_decode_32(p);
     {
         u16 flags = ceph_decode_16(p);
         info->dir_end = !!(flags & CEPH_READDIR_FRAG_END);
         info->dir_complete = !!(flags & CEPH_READDIR_FRAG_COMPLETE);
         info->hash_order = !!(flags & CEPH_READDIR_HASH_ORDER);
         info->offset_hash = !!(flags & CEPH_READDIR_OFFSET_HASH);
     }
     if (num == 0)
         goto done;
 
     BUG_ON(!info->dir_entries);
     if ((unsigned long)(info->dir_entries + num) >
         (unsigned long)info->dir_entries + info->dir_buf_size) {
         pr_err("dir contents are larger than expected\n");
         WARN_ON(1);
         goto bad;
     }
 
     info->dir_nr = num;
     while (num) {
         struct ceph_mds_reply_dir_entry *rde = info->dir_entries + i;
         /* dentry */
         ceph_decode_32_safe(p, end, rde->name_len, bad);
         ceph_decode_need(p, end, rde->name_len, bad);
         rde->name = *p;
         *p += rde->name_len;
         dout("parsed dir dname '%.*s'\n", rde->name_len, rde->name);
 
         /* dentry lease */
         err = parse_reply_info_lease(p, end, &rde->lease, features);
         if (err)
             goto out_bad;
         /* inode */
         err = parse_reply_info_in(p, end, &rde->inode, features);
         if (err < 0)
             goto out_bad;
         /* ceph_readdir_prepopulate() will update it */
         rde->offset = 0;
         i++;
         num--;
     }
 
 done:
     /* Skip over any unrecognized fields */
     *p = end;
     return 0;
 
 bad:
     err = -EIO;
 out_bad:
     pr_err("problem parsing dir contents %d\n", err);
     return err;
 }
 
 /*
  * parse fcntl F_GETLK results
  */
 static int parse_reply_info_filelock(void **p, void *end,
                      struct ceph_mds_reply_info_parsed *info,
                      u64 features)
 {
     if (*p + sizeof(*info->filelock_reply) > end)
         goto bad;
 
     info->filelock_reply = *p;
 
     /* Skip over any unrecognized fields */
     *p = end;
     return 0;
 bad:
     return -EIO;
 }
 
 
 #if BITS_PER_LONG == 64
 
 #define DELEGATED_INO_AVAILABLE     xa_mk_value(1)
 
 static int ceph_parse_deleg_inos(void **p, void *end,
                  struct ceph_mds_session *s)
 {
     u32 sets;
 
     ceph_decode_32_safe(p, end, sets, bad);
     dout("got %u sets of delegated inodes\n", sets);
     while (sets--) {
         u64 start, len;
 
         ceph_decode_64_safe(p, end, start, bad);
         ceph_decode_64_safe(p, end, len, bad);
 
         /* Don't accept a delegation of system inodes */
         if (start < CEPH_INO_SYSTEM_BASE) {
             pr_warn_ratelimited("ceph: ignoring reserved inode range delegation (start=0x%llx len=0x%llx)\n",
                     start, len);
             continue;
         }
         while (len--) {
             int err = xa_insert(&s->s_delegated_inos, start++,
                         DELEGATED_INO_AVAILABLE,
                         GFP_KERNEL);
             if (!err) {
                 dout("added delegated inode 0x%llx\n",
                      start - 1);
             } else if (err == -EBUSY) {
                 pr_warn("MDS delegated inode 0x%llx more than once.\n",
                     start - 1);
             } else {
                 return err;
             }
         }
     }
     return 0;
 bad:
     return -EIO;
 }
 
 u64 ceph_get_deleg_ino(struct ceph_mds_session *s)
 {
     unsigned long ino;
     void *val;
 
     xa_for_each(&s->s_delegated_inos, ino, val) {
         val = xa_erase(&s->s_delegated_inos, ino);
         if (val == DELEGATED_INO_AVAILABLE)
             return ino;
     }
     return 0;
 }
 
 int ceph_restore_deleg_ino(struct ceph_mds_session *s, u64 ino)
 {
     return xa_insert(&s->s_delegated_inos, ino, DELEGATED_INO_AVAILABLE,
              GFP_KERNEL);
 }
 #else /* BITS_PER_LONG == 64 */
 /*
  * FIXME: xarrays can't handle 64-bit indexes on a 32-bit arch. For now, just
  * ignore delegated_inos on 32 bit arch. Maybe eventually add xarrays for top
  * and bottom words?
  */
 static int ceph_parse_deleg_inos(void **p, void *end,
                  struct ceph_mds_session *s)
 {
     u32 sets;
 
     ceph_decode_32_safe(p, end, sets, bad);
     if (sets)
         ceph_decode_skip_n(p, end, sets * 2 * sizeof(__le64), bad);
     return 0;
 bad:
     return -EIO;
 }
 
 u64 ceph_get_deleg_ino(struct ceph_mds_session *s)
 {
     return 0;
 }
 
 int ceph_restore_deleg_ino(struct ceph_mds_session *s, u64 ino)
 {
     return 0;
 }
 #endif /* BITS_PER_LONG == 64 */
 
 /*
  * parse create results
  */
 static int parse_reply_info_create(void **p, void *end,
                   struct ceph_mds_reply_info_parsed *info,
                   u64 features, struct ceph_mds_session *s)
 {
     int ret;
 
     if (features == (u64)-1 ||
         (features & CEPH_FEATURE_REPLY_CREATE_INODE)) {
         if (*p == end) {
             /* Malformed reply? */
             info->has_create_ino = false;
         } else if (test_bit(CEPHFS_FEATURE_DELEG_INO, &s->s_features)) {
             info->has_create_ino = true;
             /* struct_v, struct_compat, and len */
             ceph_decode_skip_n(p, end, 2 + sizeof(u32), bad);
             ceph_decode_64_safe(p, end, info->ino, bad);
             ret = ceph_parse_deleg_inos(p, end, s);
             if (ret)
                 return ret;
         } else {
             /* legacy */
             ceph_decode_64_safe(p, end, info->ino, bad);
             info->has_create_ino = true;
         }
     } else {
         if (*p != end)
             goto bad;
     }
 
     /* Skip over any unrecognized fields */
     *p = end;
     return 0;
 bad:
     return -EIO;
 }
 
 static int parse_reply_info_getvxattr(void **p, void *end,
                       struct ceph_mds_reply_info_parsed *info,
                       u64 features)
 {
     u32 value_len;
 
     ceph_decode_skip_8(p, end, bad); /* skip current version: 1 */
     ceph_decode_skip_8(p, end, bad); /* skip first version: 1 */
     ceph_decode_skip_32(p, end, bad); /* skip payload length */
 
     ceph_decode_32_safe(p, end, value_len, bad);
 
     if (value_len == end - *p) {
       info->xattr_info.xattr_value = *p;
       info->xattr_info.xattr_value_len = value_len;
       *p = end;
       return value_len;
     }
 bad:
     return -EIO;
 }
 
 /*
  * parse extra results
  */
 static int parse_reply_info_extra(void **p, void *end,
                   struct ceph_mds_reply_info_parsed *info,
                   u64 features, struct ceph_mds_session *s)
 {
     u32 op = le32_to_cpu(info->head->op);
 
     if (op == CEPH_MDS_OP_GETFILELOCK)
         return parse_reply_info_filelock(p, end, info, features);
     else if (op == CEPH_MDS_OP_READDIR || op == CEPH_MDS_OP_LSSNAP)
         return parse_reply_info_readdir(p, end, info, features);
     else if (op == CEPH_MDS_OP_CREATE)
         return parse_reply_info_create(p, end, info, features, s);
     else if (op == CEPH_MDS_OP_GETVXATTR)
         return parse_reply_info_getvxattr(p, end, info, features);
     else
         return -EIO;
 }
 
 /*
  * parse entire mds reply
  */
 static int parse_reply_info(struct ceph_mds_session *s, struct ceph_msg *msg,
                 struct ceph_mds_reply_info_parsed *info,
                 u64 features)
 {
     void *p, *end;
     u32 len;
     int err;
 
     info->head = msg->front.iov_base;
     p = msg->front.iov_base + sizeof(struct ceph_mds_reply_head);
     end = p + msg->front.iov_len - sizeof(struct ceph_mds_reply_head);
 
     /* trace */
     ceph_decode_32_safe(&p, end, len, bad);
     if (len > 0) {
         ceph_decode_need(&p, end, len, bad);
         err = parse_reply_info_trace(&p, p+len, info, features);
         if (err < 0)
             goto out_bad;
     }
 
     /* extra */
     ceph_decode_32_safe(&p, end, len, bad);
     if (len > 0) {
         ceph_decode_need(&p, end, len, bad);
         err = parse_reply_info_extra(&p, p+len, info, features, s);
         if (err < 0)
             goto out_bad;
     }
 
     /* snap blob */
     ceph_decode_32_safe(&p, end, len, bad);
     info->snapblob_len = len;
     info->snapblob = p;
     p += len;
 
     if (p != end)
         goto bad;
     return 0;
 
 bad:
     err = -EIO;
 out_bad:
     pr_err("mds parse_reply err %d\n", err);
     return err;
 }
 
 static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
 {
     if (!info->dir_entries)
         return;
     free_pages((unsigned long)info->dir_entries, get_order(info->dir_buf_size));
 }
 
 /*
  * In async unlink case the kclient won't wait for the first reply
  * from MDS and just drop all the links and unhash the dentry and then
  * succeeds immediately.
  *
  * For any new create/link/rename,etc requests followed by using the
  * same file names we must wait for the first reply of the inflight
  * unlink request, or the MDS possibly will fail these following
  * requests with -EEXIST if the inflight async unlink request was
  * delayed for some reasons.
  *
  * And the worst case is that for the none async openc request it will
  * successfully open the file if the CDentry hasn't been unlinked yet,
  * but later the previous delayed async unlink request will remove the
  * CDenty. That means the just created file is possiblly deleted later
  * by accident.
  *
  * We need to wait for the inflight async unlink requests to finish
  * when creating new files/directories by using the same file names.
  */
 int ceph_wait_on_conflict_unlink(struct dentry *dentry)
 {
     struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
     struct dentry *pdentry = dentry->d_parent;
     struct dentry *udentry, *found = NULL;
     struct ceph_dentry_info *di;
     struct qstr dname;
     u32 hash = dentry->d_name.hash;
     int err;
 
     dname.name = dentry->d_name.name;
     dname.len = dentry->d_name.len;
 
     rcu_read_lock();
     hash_for_each_possible_rcu(fsc->async_unlink_conflict, di,
                    hnode, hash) {
         udentry = di->dentry;
 
         spin_lock(&udentry->d_lock);
         if (udentry->d_name.hash != hash)
             goto next;
         if (unlikely(udentry->d_parent != pdentry))
             goto next;
         if (!hash_hashed(&di->hnode))
             goto next;
 
         if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags))
             pr_warn("%s dentry %p:%pd async unlink bit is not set\n",
                 __func__, dentry, dentry);
 
         if (!d_same_name(udentry, pdentry, &dname))
             goto next;
 
         spin_unlock(&udentry->d_lock);
         found = dget(udentry);
         break;
 next:
         spin_unlock(&udentry->d_lock);
     }
     rcu_read_unlock();
 
     if (likely(!found))
         return 0;
 
     dout("%s dentry %p:%pd conflict with old %p:%pd\n", __func__,
          dentry, dentry, found, found);
 
     err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT,
               TASK_KILLABLE);
     dput(found);
     return err;
 }
 
 
 /*
  * sessions
  */
 const char *ceph_session_state_name(int s)
 {
     switch (s) {
     case CEPH_MDS_SESSION_NEW: return "new";
     case CEPH_MDS_SESSION_OPENING: return "opening";
     case CEPH_MDS_SESSION_OPEN: return "open";
     case CEPH_MDS_SESSION_HUNG: return "hung";
     case CEPH_MDS_SESSION_CLOSING: return "closing";
     case CEPH_MDS_SESSION_CLOSED: return "closed";
     case CEPH_MDS_SESSION_RESTARTING: return "restarting";
     case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
     case CEPH_MDS_SESSION_REJECTED: return "rejected";
     default: return "???";
     }
 }
 
 struct ceph_mds_session *ceph_get_mds_session(struct ceph_mds_session *s)
 {
     if (refcount_inc_not_zero(&s->s_ref))
         return s;
     return NULL;
 }
 
 void ceph_put_mds_session(struct ceph_mds_session *s)
 {
     if (IS_ERR_OR_NULL(s))
         return;
 
     if (refcount_dec_and_test(&s->s_ref)) {
         if (s->s_auth.authorizer)
             ceph_auth_destroy_authorizer(s->s_auth.authorizer);
         WARN_ON(mutex_is_locked(&s->s_mutex));
         xa_destroy(&s->s_delegated_inos);
         kfree(s);
     }
 }
 
 /*
  * called under mdsc->mutex
  */
 struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
                            int mds)
 {
     if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
         return NULL;
     return ceph_get_mds_session(mdsc->sessions[mds]);
 }
 
 static bool __have_session(struct ceph_mds_client *mdsc, int mds)
 {
     if (mds >= mdsc->max_sessions || !mdsc->sessions[mds])
         return false;
     else
         return true;
 }
 
 static int __verify_registered_session(struct ceph_mds_client *mdsc,
                        struct ceph_mds_session *s)
 {
     if (s->s_mds >= mdsc->max_sessions ||
         mdsc->sessions[s->s_mds] != s)
         return -ENOENT;
     return 0;
 }
 
 /*
  * create+register a new session for given mds.
  * called under mdsc->mutex.
  */
 static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
                          int mds)
 {
     struct ceph_mds_session *s;
 
     if (mds >= mdsc->mdsmap->possible_max_rank)
         return ERR_PTR(-EINVAL);
 
     s = kzalloc(sizeof(*s), GFP_NOFS);
     if (!s)
         return ERR_PTR(-ENOMEM);
 
     if (mds >= mdsc->max_sessions) {
         int newmax = 1 << get_count_order(mds + 1);
         struct ceph_mds_session **sa;
 
         dout("%s: realloc to %d\n", __func__, newmax);
         sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
         if (!sa)
             goto fail_realloc;
         if (mdsc->sessions) {
             memcpy(sa, mdsc->sessions,
                    mdsc->max_sessions * sizeof(void *));
             kfree(mdsc->sessions);
         }
         mdsc->sessions = sa;
         mdsc->max_sessions = newmax;
     }
 
     dout("%s: mds%d\n", __func__, mds);
     s->s_mdsc = mdsc;
     s->s_mds = mds;
     s->s_state = CEPH_MDS_SESSION_NEW;
     mutex_init(&s->s_mutex);
 
     ceph_con_init(&s->s_con, s, &mds_con_ops, &mdsc->fsc->client->msgr);
 
     atomic_set(&s->s_cap_gen, 1);
     s->s_cap_ttl = jiffies - 1;
 
     spin_lock_init(&s->s_cap_lock);
     INIT_LIST_HEAD(&s->s_caps);
     refcount_set(&s->s_ref, 1);
     INIT_LIST_HEAD(&s->s_waiting);
     INIT_LIST_HEAD(&s->s_unsafe);
     xa_init(&s->s_delegated_inos);
     INIT_LIST_HEAD(&s->s_cap_releases);
     INIT_WORK(&s->s_cap_release_work, ceph_cap_release_work);
 
     INIT_LIST_HEAD(&s->s_cap_dirty);
     INIT_LIST_HEAD(&s->s_cap_flushing);
 
     mdsc->sessions[mds] = s;
     atomic_inc(&mdsc->num_sessions);
     refcount_inc(&s->s_ref);  /* one ref to sessions[], one to caller */
 
     ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
               ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
 
     return s;
 
 fail_realloc:
     kfree(s);
     return ERR_PTR(-ENOMEM);
 }
 
 /*
  * called under mdsc->mutex
  */
 static void __unregister_session(struct ceph_mds_client *mdsc,
                    struct ceph_mds_session *s)
 {
     dout("__unregister_session mds%d %p\n", s->s_mds, s);
     BUG_ON(mdsc->sessions[s->s_mds] != s);
     mdsc->sessions[s->s_mds] = NULL;
     ceph_con_close(&s->s_con);
     ceph_put_mds_session(s);
     atomic_dec(&mdsc->num_sessions);
 }
 
 /*
  * drop session refs in request.
  *
  * should be last request ref, or hold mdsc->mutex
  */
 static void put_request_session(struct ceph_mds_request *req)
 {
     if (req->r_session) {
         ceph_put_mds_session(req->r_session);
         req->r_session = NULL;
     }
 }
 
 void ceph_mdsc_iterate_sessions(struct ceph_mds_client *mdsc,
                 void (*cb)(struct ceph_mds_session *),
                 bool check_state)
 {
     int mds;
 
     mutex_lock(&mdsc->mutex);
     for (mds = 0; mds < mdsc->max_sessions; ++mds) {
         struct ceph_mds_session *s;
 
         s = __ceph_lookup_mds_session(mdsc, mds);
         if (!s)
             continue;
 
         if (check_state && !check_session_state(s)) {
             ceph_put_mds_session(s);
             continue;
         }
 
         mutex_unlock(&mdsc->mutex);
         cb(s);
         ceph_put_mds_session(s);
         mutex_lock(&mdsc->mutex);
     }
     mutex_unlock(&mdsc->mutex);
 }
 
 void ceph_mdsc_release_request(struct kref *kref)
 {
     struct ceph_mds_request *req = container_of(kref,
                             struct ceph_mds_request,
                             r_kref);
     ceph_mdsc_release_dir_caps_no_check(req);
     destroy_reply_info(&req->r_reply_info);
     if (req->r_request)
         ceph_msg_put(req->r_request);
     if (req->r_reply)
         ceph_msg_put(req->r_reply);
     if (req->r_inode) {
         ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
         iput(req->r_inode);
     }
     if (req->r_parent) {
         ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN);
         iput(req->r_parent);
     }
     iput(req->r_target_inode);
     if (req->r_dentry)
         dput(req->r_dentry);
     if (req->r_old_dentry)
         dput(req->r_old_dentry);
     if (req->r_old_dentry_dir) {
         /*
          * track (and drop pins for) r_old_dentry_dir
          * separately, since r_old_dentry's d_parent may have
          * changed between the dir mutex being dropped and
          * this request being freed.
          */
         ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
                   CEPH_CAP_PIN);
         iput(req->r_old_dentry_dir);
     }
     kfree(req->r_path1);
     kfree(req->r_path2);
     put_cred(req->r_cred);
     if (req->r_pagelist)
         ceph_pagelist_release(req->r_pagelist);
     put_request_session(req);
     ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
     WARN_ON_ONCE(!list_empty(&req->r_wait));
     kmem_cache_free(ceph_mds_request_cachep, req);
 }
 
 DEFINE_RB_FUNCS(request, struct ceph_mds_request, r_tid, r_node)
 
 /*
  * lookup session, bump ref if found.
  *
  * called under mdsc->mutex.
  */
 static struct ceph_mds_request *
 lookup_get_request(struct ceph_mds_client *mdsc, u64 tid)
 {
     struct ceph_mds_request *req;
 
     req = lookup_request(&mdsc->request_tree, tid);
     if (req)
         ceph_mdsc_get_request(req);
 
     return req;
 }
 
 /*
  * Register an in-flight request, and assign a tid.  Link to directory
  * are modifying (if any).
  *
  * Called under mdsc->mutex.
  */
 static void __register_request(struct ceph_mds_client *mdsc,
                    struct ceph_mds_request *req,
                    struct inode *dir)
 {
     int ret = 0;
 
     req->r_tid = ++mdsc->last_tid;
     if (req->r_num_caps) {
         ret = ceph_reserve_caps(mdsc, &req->r_caps_reservation,
                     req->r_num_caps);
         if (ret < 0) {
             pr_err("__register_request %p "
                    "failed to reserve caps: %d\n", req, ret);
             /* set req->r_err to fail early from __do_request */
             req->r_err = ret;
             return;
         }
     }
     dout("__register_request %p tid %lld\n", req, req->r_tid);
     ceph_mdsc_get_request(req);
     insert_request(&mdsc->request_tree, req);
 
     req->r_cred = get_current_cred();
 
     if (mdsc->oldest_tid == 0 && req->r_op != CEPH_MDS_OP_SETFILELOCK)
         mdsc->oldest_tid = req->r_tid;
 
     if (dir) {
         struct ceph_inode_info *ci = ceph_inode(dir);
 
         ihold(dir);
         req->r_unsafe_dir = dir;
         spin_lock(&ci->i_unsafe_lock);
         list_add_tail(&req->r_unsafe_dir_item, &ci->i_unsafe_dirops);
         spin_unlock(&ci->i_unsafe_lock);
     }
 }
 
 static void __unregister_request(struct ceph_mds_client *mdsc,
                  struct ceph_mds_request *req)
 {
     dout("__unregister_request %p tid %lld\n", req, req->r_tid);
 
     /* Never leave an unregistered request on an unsafe list! */
     list_del_init(&req->r_unsafe_item);
 
     if (req->r_tid == mdsc->oldest_tid) {
         struct rb_node *p = rb_next(&req->r_node);
         mdsc->oldest_tid = 0;
         while (p) {
             struct ceph_mds_request *next_req =
                 rb_entry(p, struct ceph_mds_request, r_node);
             if (next_req->r_op != CEPH_MDS_OP_SETFILELOCK) {
                 mdsc->oldest_tid = next_req->r_tid;
                 break;
             }
             p = rb_next(p);
         }
     }
 
     erase_request(&mdsc->request_tree, req);
 
     if (req->r_unsafe_dir) {
         struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);
         spin_lock(&ci->i_unsafe_lock);
         list_del_init(&req->r_unsafe_dir_item);
         spin_unlock(&ci->i_unsafe_lock);
     }
     if (req->r_target_inode &&
         test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
         struct ceph_inode_info *ci = ceph_inode(req->r_target_inode);
         spin_lock(&ci->i_unsafe_lock);
         list_del_init(&req->r_unsafe_target_item);
         spin_unlock(&ci->i_unsafe_lock);
     }
 
     if (req->r_unsafe_dir) {
         iput(req->r_unsafe_dir);
         req->r_unsafe_dir = NULL;
     }
 
     complete_all(&req->r_safe_completion);
 
     ceph_mdsc_put_request(req);
 }
 
 /*
  * Walk back up the dentry tree until we hit a dentry representing a
  * non-snapshot inode. We do this using the rcu_read_lock (which must be held
  * when calling this) to ensure that the objects won't disappear while we're
  * working with them. Once we hit a candidate dentry, we attempt to take a
  * reference to it, and return that as the result.
  */
 static struct inode *get_nonsnap_parent(struct dentry *dentry)
 {
     struct inode *inode = NULL;
 
     while (dentry && !IS_ROOT(dentry)) {
         inode = d_inode_rcu(dentry);
         if (!inode || ceph_snap(inode) == CEPH_NOSNAP)
             break;
         dentry = dentry->d_parent;
     }
     if (inode)
         inode = igrab(inode);
     return inode;
 }
 
 /*
  * Choose mds to send request to next.  If there is a hint set in the
  * request (e.g., due to a prior forward hint from the mds), use that.
  * Otherwise, consult frag tree and/or caps to identify the
  * appropriate mds.  If all else fails, choose randomly.
  *
  * Called under mdsc->mutex.
  */
 static int __choose_mds(struct ceph_mds_client *mdsc,
             struct ceph_mds_request *req,
             bool *random)
 {
     struct inode *inode;
     struct ceph_inode_info *ci;
     struct ceph_cap *cap;
     int mode = req->r_direct_mode;
     int mds = -1;
     u32 hash = req->r_direct_hash;
     bool is_hash = test_bit(CEPH_MDS_R_DIRECT_IS_HASH, &req->r_req_flags);
 
     if (random)
         *random = false;
 
     /*
      * is there a specific mds we should try?  ignore hint if we have
      * no session and the mds is not up (active or recovering).
      */
     if (req->r_resend_mds >= 0 &&
         (__have_session(mdsc, req->r_resend_mds) ||
          ceph_mdsmap_get_state(mdsc->mdsmap, req->r_resend_mds) > 0)) {
         dout("%s using resend_mds mds%d\n", __func__,
              req->r_resend_mds);
         return req->r_resend_mds;
     }
 
     if (mode == USE_RANDOM_MDS)
         goto random;
 
     inode = NULL;
     if (req->r_inode) {
         if (ceph_snap(req->r_inode) != CEPH_SNAPDIR) {
             inode = req->r_inode;
             ihold(inode);
         } else {
             /* req->r_dentry is non-null for LSSNAP request */
             rcu_read_lock();
             inode = get_nonsnap_parent(req->r_dentry);
             rcu_read_unlock();
             dout("%s using snapdir's parent %p\n", __func__, inode);
         }
     } else if (req->r_dentry) {
         /* ignore race with rename; old or new d_parent is okay */
         struct dentry *parent;
         struct inode *dir;
 
         rcu_read_lock();
         parent = READ_ONCE(req->r_dentry->d_parent);
         dir = req->r_parent ? : d_inode_rcu(parent);
 
         if (!dir || dir->i_sb != mdsc->fsc->sb) {
             /*  not this fs or parent went negative */
             inode = d_inode(req->r_dentry);
             if (inode)
                 ihold(inode);
         } else if (ceph_snap(dir) != CEPH_NOSNAP) {
             /* direct snapped/virtual snapdir requests
              * based on parent dir inode */
             inode = get_nonsnap_parent(parent);
             dout("%s using nonsnap parent %p\n", __func__, inode);
         } else {
             /* dentry target */
             inode = d_inode(req->r_dentry);
             if (!inode || mode == USE_AUTH_MDS) {
                 /* dir + name */
                 inode = igrab(dir);
                 hash = ceph_dentry_hash(dir, req->r_dentry);
                 is_hash = true;
             } else {
                 ihold(inode);
             }
         }
         rcu_read_unlock();
     }
 
     dout("%s %p is_hash=%d (0x%x) mode %d\n", __func__, inode, (int)is_hash,
          hash, mode);
     if (!inode)
         goto random;
     ci = ceph_inode(inode);
 
     if (is_hash && S_ISDIR(inode->i_mode)) {
         struct ceph_inode_frag frag;
         int found;
 
         ceph_choose_frag(ci, hash, &frag, &found);
         if (found) {
             if (mode == USE_ANY_MDS && frag.ndist > 0) {
                 u8 r;
 
                 /* choose a random replica */
                 get_random_bytes(&r, 1);
                 r %= frag.ndist;
                 mds = frag.dist[r];
                 dout("%s %p %llx.%llx frag %u mds%d (%d/%d)\n",
                      __func__, inode, ceph_vinop(inode),
                      frag.frag, mds, (int)r, frag.ndist);
                 if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                     CEPH_MDS_STATE_ACTIVE &&
                     !ceph_mdsmap_is_laggy(mdsc->mdsmap, mds))
                     goto out;
             }
 
             /* since this file/dir wasn't known to be
              * replicated, then we want to look for the
              * authoritative mds. */
             if (frag.mds >= 0) {
                 /* choose auth mds */
                 mds = frag.mds;
                 dout("%s %p %llx.%llx frag %u mds%d (auth)\n",
                      __func__, inode, ceph_vinop(inode),
                      frag.frag, mds);
                 if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                     CEPH_MDS_STATE_ACTIVE) {
                     if (!ceph_mdsmap_is_laggy(mdsc->mdsmap,
                                   mds))
                         goto out;
                 }
             }
             mode = USE_AUTH_MDS;
         }
     }
 
     spin_lock(&ci->i_ceph_lock);
     cap = NULL;
     if (mode == USE_AUTH_MDS)
         cap = ci->i_auth_cap;
     if (!cap && !RB_EMPTY_ROOT(&ci->i_caps))
         cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
     if (!cap) {
         spin_unlock(&ci->i_ceph_lock);
         iput(inode);
         goto random;
     }
     mds = cap->session->s_mds;
     dout("%s %p %llx.%llx mds%d (%scap %p)\n", __func__,
          inode, ceph_vinop(inode), mds,
          cap == ci->i_auth_cap ? "auth " : "", cap);
     spin_unlock(&ci->i_ceph_lock);
 out:
     iput(inode);
     return mds;
 
 random:
     if (random)
         *random = true;
 
     mds = ceph_mdsmap_get_random_mds(mdsc->mdsmap);
     dout("%s chose random mds%d\n", __func__, mds);
     return mds;
 }
 
 
 /*
  * session messages
  */
 struct ceph_msg *ceph_create_session_msg(u32 op, u64 seq)
 {
     struct ceph_msg *msg;
     struct ceph_mds_session_head *h;
 
     msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h), GFP_NOFS,
                false);
     if (!msg) {
         pr_err("ENOMEM creating session %s msg\n",
                ceph_session_op_name(op));
         return NULL;
     }
     h = msg->front.iov_base;
     h->op = cpu_to_le32(op);
     h->seq = cpu_to_le64(seq);
 
     return msg;
 }
 
 static const unsigned char feature_bits[] = CEPHFS_FEATURES_CLIENT_SUPPORTED;
 #define FEATURE_BYTES(c) (DIV_ROUND_UP((size_t)feature_bits[c - 1] + 1, 64) * 8)
 static int encode_supported_features(void **p, void *end)
 {
     static const size_t count = ARRAY_SIZE(feature_bits);
 
     if (count > 0) {
         size_t i;
         size_t size = FEATURE_BYTES(count);
         unsigned long bit;
 
         if (WARN_ON_ONCE(*p + 4 + size > end))
             return -ERANGE;
 
         ceph_encode_32(p, size);
         memset(*p, 0, size);
         for (i = 0; i < count; i++) {
             bit = feature_bits[i];
             ((unsigned char *)(*p))[bit / 8] |= BIT(bit % 8);
         }
         *p += size;
     } else {
         if (WARN_ON_ONCE(*p + 4 > end))
             return -ERANGE;
 
         ceph_encode_32(p, 0);
     }
 
     return 0;
 }
 
 static const unsigned char metric_bits[] = CEPHFS_METRIC_SPEC_CLIENT_SUPPORTED;
 #define METRIC_BYTES(cnt) (DIV_ROUND_UP((size_t)metric_bits[cnt - 1] + 1, 64) * 8)
 static int encode_metric_spec(void **p, void *end)
 {
     static const size_t count = ARRAY_SIZE(metric_bits);
 
     /* header */
     if (WARN_ON_ONCE(*p + 2 > end))
         return -ERANGE;
 
     ceph_encode_8(p, 1); /* version */
     ceph_encode_8(p, 1); /* compat */
 
     if (count > 0) {
         size_t i;
         size_t size = METRIC_BYTES(count);
 
         if (WARN_ON_ONCE(*p + 4 + 4 + size > end))
             return -ERANGE;
 
         /* metric spec info length */
         ceph_encode_32(p, 4 + size);
 
         /* metric spec */
         ceph_encode_32(p, size);
         memset(*p, 0, size);
         for (i = 0; i < count; i++)
             ((unsigned char *)(*p))[i / 8] |= BIT(metric_bits[i] % 8);
         *p += size;
     } else {
         if (WARN_ON_ONCE(*p + 4 + 4 > end))
             return -ERANGE;
 
         /* metric spec info length */
         ceph_encode_32(p, 4);
         /* metric spec */
         ceph_encode_32(p, 0);
     }
 
     return 0;
 }
 
 /*
  * session message, specialization for CEPH_SESSION_REQUEST_OPEN
  * to include additional client metadata fields.
  */
 static struct ceph_msg *create_session_open_msg(struct ceph_mds_client *mdsc, u64 seq)
 {
     struct ceph_msg *msg;
     struct ceph_mds_session_head *h;
     int i;
     int extra_bytes = 0;
     int metadata_key_count = 0;
     struct ceph_options *opt = mdsc->fsc->client->options;
     struct ceph_mount_options *fsopt = mdsc->fsc->mount_options;
     size_t size, count;
     void *p, *end;
     int ret;
 
     const char* metadata[][2] = {
         {"hostname", mdsc->nodename},
         {"kernel_version", init_utsname()->release},
         {"entity_id", opt->name ? : ""},
         {"root", fsopt->server_path ? : "/"},
         {NULL, NULL}
     };
 
     /* Calculate serialized length of metadata */
     extra_bytes = 4;  /* map length */
     for (i = 0; metadata[i][0]; ++i) {
         extra_bytes += 8 + strlen(metadata[i][0]) +
             strlen(metadata[i][1]);
         metadata_key_count++;
     }
 
     /* supported feature */
     size = 0;
     count = ARRAY_SIZE(feature_bits);
     if (count > 0)
         size = FEATURE_BYTES(count);
     extra_bytes += 4 + size;
 
     /* metric spec */
     size = 0;
     count = ARRAY_SIZE(metric_bits);
     if (count > 0)
         size = METRIC_BYTES(count);
     extra_bytes += 2 + 4 + 4 + size;
 
     /* Allocate the message */
     msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h) + extra_bytes,
                GFP_NOFS, false);
     if (!msg) {
         pr_err("ENOMEM creating session open msg\n");
         return ERR_PTR(-ENOMEM);
     }
     p = msg->front.iov_base;
     end = p + msg->front.iov_len;
 
     h = p;
     h->op = cpu_to_le32(CEPH_SESSION_REQUEST_OPEN);
     h->seq = cpu_to_le64(seq);
 
     /*
      * Serialize client metadata into waiting buffer space, using
      * the format that userspace expects for map<string, string>
      *
      * ClientSession messages with metadata are v4
      */
     msg->hdr.version = cpu_to_le16(4);
     msg->hdr.compat_version = cpu_to_le16(1);
 
     /* The write pointer, following the session_head structure */
     p += sizeof(*h);
 
     /* Number of entries in the map */
     ceph_encode_32(&p, metadata_key_count);
 
     /* Two length-prefixed strings for each entry in the map */
     for (i = 0; metadata[i][0]; ++i) {
         size_t const key_len = strlen(metadata[i][0]);
         size_t const val_len = strlen(metadata[i][1]);
 
         ceph_encode_32(&p, key_len);
         memcpy(p, metadata[i][0], key_len);
         p += key_len;
         ceph_encode_32(&p, val_len);
         memcpy(p, metadata[i][1], val_len);
         p += val_len;
     }
 
     ret = encode_supported_features(&p, end);
     if (ret) {
         pr_err("encode_supported_features failed!\n");
         ceph_msg_put(msg);
         return ERR_PTR(ret);
     }
 
     ret = encode_metric_spec(&p, end);
     if (ret) {
         pr_err("encode_metric_spec failed!\n");
         ceph_msg_put(msg);
         return ERR_PTR(ret);
     }
 
     msg->front.iov_len = p - msg->front.iov_base;
     msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
 
     return msg;
 }
 
 /*
  * send session open request.
  *
  * called under mdsc->mutex
  */
 static int __open_session(struct ceph_mds_client *mdsc,
               struct ceph_mds_session *session)
 {
     struct ceph_msg *msg;
     int mstate;
     int mds = session->s_mds;
 
     /* wait for mds to go active? */
     mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
     dout("open_session to mds%d (%s)\n", mds,
          ceph_mds_state_name(mstate));
     session->s_state = CEPH_MDS_SESSION_OPENING;
     session->s_renew_requested = jiffies;
 
     /* send connect message */
     msg = create_session_open_msg(mdsc, session->s_seq);
     if (IS_ERR(msg))
         return PTR_ERR(msg);
     ceph_con_send(&session->s_con, msg);
     return 0;
 }
 
 /*
  * open sessions for any export targets for the given mds
  *
  * called under mdsc->mutex
  */
 static struct ceph_mds_session *
 __open_export_target_session(struct ceph_mds_client *mdsc, int target)
 {
     struct ceph_mds_session *session;
     int ret;
 
     session = __ceph_lookup_mds_session(mdsc, target);
     if (!session) {
         session = register_session(mdsc, target);
         if (IS_ERR(session))
             return session;
     }
     if (session->s_state == CEPH_MDS_SESSION_NEW ||
         session->s_state == CEPH_MDS_SESSION_CLOSING) {
         ret = __open_session(mdsc, session);
         if (ret)
             return ERR_PTR(ret);
     }
 
     return session;
 }
 
 struct ceph_mds_session *
 ceph_mdsc_open_export_target_session(struct ceph_mds_client *mdsc, int target)
 {
     struct ceph_mds_session *session;
 
     dout("open_export_target_session to mds%d\n", target);
 
     mutex_lock(&mdsc->mutex);
     session = __open_export_target_session(mdsc, target);
     mutex_unlock(&mdsc->mutex);
 
     return session;
 }
 
 static void __open_export_target_sessions(struct ceph_mds_client *mdsc,
                       struct ceph_mds_session *session)
 {
     struct ceph_mds_info *mi;
     struct ceph_mds_session *ts;
     int i, mds = session->s_mds;
 
     if (mds >= mdsc->mdsmap->possible_max_rank)
         return;
 
     mi = &mdsc->mdsmap->m_info[mds];
     dout("open_export_target_sessions for mds%d (%d targets)\n",
          session->s_mds, mi->num_export_targets);
 
     for (i = 0; i < mi->num_export_targets; i++) {
         ts = __open_export_target_session(mdsc, mi->export_targets[i]);
         ceph_put_mds_session(ts);
     }
 }
 
 void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
                        struct ceph_mds_session *session)
 {
     mutex_lock(&mdsc->mutex);
     __open_export_target_sessions(mdsc, session);
     mutex_unlock(&mdsc->mutex);
 }
 
 /*
  * session caps
  */
 
 static void detach_cap_releases(struct ceph_mds_session *session,
                 struct list_head *target)
 {
     lockdep_assert_held(&session->s_cap_lock);
 
     list_splice_init(&session->s_cap_releases, target);
     session->s_num_cap_releases = 0;
     dout("dispose_cap_releases mds%d\n", session->s_mds);
 }
 
 static void dispose_cap_releases(struct ceph_mds_client *mdsc,
                  struct list_head *dispose)
 {
     while (!list_empty(dispose)) {
         struct ceph_cap *cap;
         /* zero out the in-progress message */
         cap = list_first_entry(dispose, struct ceph_cap, session_caps);
         list_del(&cap->session_caps);
         ceph_put_cap(mdsc, cap);
     }
 }
 
 static void cleanup_session_requests(struct ceph_mds_client *mdsc,
                      struct ceph_mds_session *session)
 {
     struct ceph_mds_request *req;
     struct rb_node *p;
 
     dout("cleanup_session_requests mds%d\n", session->s_mds);
     mutex_lock(&mdsc->mutex);
     while (!list_empty(&session->s_unsafe)) {
         req = list_first_entry(&session->s_unsafe,
                        struct ceph_mds_request, r_unsafe_item);
         pr_warn_ratelimited(" dropping unsafe request %llu\n",
                     req->r_tid);
         if (req->r_target_inode)
             mapping_set_error(req->r_target_inode->i_mapping, -EIO);
         if (req->r_unsafe_dir)
             mapping_set_error(req->r_unsafe_dir->i_mapping, -EIO);
         __unregister_request(mdsc, req);
     }
     /* zero r_attempts, so kick_requests() will re-send requests */
     p = rb_first(&mdsc->request_tree);
     while (p) {
         req = rb_entry(p, struct ceph_mds_request, r_node);
         p = rb_next(p);
         if (req->r_session &&
             req->r_session->s_mds == session->s_mds)
             req->r_attempts = 0;
     }
     mutex_unlock(&mdsc->mutex);
 }
 
 /*
  * Helper to safely iterate over all caps associated with a session, with
  * special care taken to handle a racing __ceph_remove_cap().
  *
  * Caller must hold session s_mutex.
  */
 int ceph_iterate_session_caps(struct ceph_mds_session *session,
                   int (*cb)(struct inode *, struct ceph_cap *,
                     void *), void *arg)
 {
     struct list_head *p;
     struct ceph_cap *cap;
     struct inode *inode, *last_inode = NULL;
     struct ceph_cap *old_cap = NULL;
     int ret;
 
     dout("iterate_session_caps %p mds%d\n", session, session->s_mds);
     spin_lock(&session->s_cap_lock);
     p = session->s_caps.next;
     while (p != &session->s_caps) {
         cap = list_entry(p, struct ceph_cap, session_caps);
         inode = igrab(&cap->ci->netfs.inode);
         if (!inode) {
             p = p->next;
             continue;
         }
         session->s_cap_iterator = cap;
         spin_unlock(&session->s_cap_lock);
 
         if (last_inode) {
             iput(last_inode);
             last_inode = NULL;
         }
         if (old_cap) {
             ceph_put_cap(session->s_mdsc, old_cap);
             old_cap = NULL;
         }
 
         ret = cb(inode, cap, arg);
         last_inode = inode;
 
         spin_lock(&session->s_cap_lock);
         p = p->next;
         if (!cap->ci) {
             dout("iterate_session_caps  finishing cap %p removal\n",
                  cap);
             BUG_ON(cap->session != session);
             cap->session = NULL;
             list_del_init(&cap->session_caps);
             session->s_nr_caps--;
             atomic64_dec(&session->s_mdsc->metric.total_caps);
             if (cap->queue_release)
                 __ceph_queue_cap_release(session, cap);
             else
                 old_cap = cap;  /* put_cap it w/o locks held */
         }
         if (ret < 0)
             goto out;
     }
     ret = 0;
 out:
     session->s_cap_iterator = NULL;
     spin_unlock(&session->s_cap_lock);
 
     iput(last_inode);
     if (old_cap)
         ceph_put_cap(session->s_mdsc, old_cap);
 
     return ret;
 }
 
 static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
                   void *arg)
 {
     struct ceph_inode_info *ci = ceph_inode(inode);
     bool invalidate = false;
     int iputs;
 
     dout("removing cap %p, ci is %p, inode is %p\n",
          cap, ci, &ci->netfs.inode);
     spin_lock(&ci->i_ceph_lock);
     iputs = ceph_purge_inode_cap(inode, cap, &invalidate);
     spin_unlock(&ci->i_ceph_lock);
 
     wake_up_all(&ci->i_cap_wq);
     if (invalidate)
         ceph_queue_invalidate(inode);
     while (iputs--)
         iput(inode);
     return 0;
 }
 
 /*
  * caller must hold session s_mutex
  */
 static void remove_session_caps(struct ceph_mds_session *session)
 {
     struct ceph_fs_client *fsc = session->s_mdsc->fsc;
     struct super_block *sb = fsc->sb;
     LIST_HEAD(dispose);
 
     dout("remove_session_caps on %p\n", session);
     ceph_iterate_session_caps(session, remove_session_caps_cb, fsc);
 
     wake_up_all(&fsc->mdsc->cap_flushing_wq);
 
     spin_lock(&session->s_cap_lock);
     if (session->s_nr_caps > 0) {
         struct inode *inode;
         struct ceph_cap *cap, *prev = NULL;
         struct ceph_vino vino;
         /*
          * iterate_session_caps() skips inodes that are being
          * deleted, we need to wait until deletions are complete.
          * __wait_on_freeing_inode() is designed for the job,
          * but it is not exported, so use lookup inode function
          * to access it.
          */
         while (!list_empty(&session->s_caps)) {
             cap = list_entry(session->s_caps.next,
                      struct ceph_cap, session_caps);
             if (cap == prev)
                 break;
             prev = cap;
             vino = cap->ci->i_vino;
             spin_unlock(&session->s_cap_lock);
 
             inode = ceph_find_inode(sb, vino);
             iput(inode);
 
             spin_lock(&session->s_cap_lock);
         }
     }
 
     // drop cap expires and unlock s_cap_lock
     detach_cap_releases(session, &dispose);
 
     BUG_ON(session->s_nr_caps > 0);
     BUG_ON(!list_empty(&session->s_cap_flushing));
     spin_unlock(&session->s_cap_lock);
     dispose_cap_releases(session->s_mdsc, &dispose);
 }
 
 enum {
     RECONNECT,
     RENEWCAPS,
     FORCE_RO,
 };
 
 /*
  * wake up any threads waiting on this session's caps.  if the cap is
  * old (didn't get renewed on the client reconnect), remove it now.
  *
  * caller must hold s_mutex.
  */
 static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
                   void *arg)
 {
     struct ceph_inode_info *ci = ceph_inode(inode);
     unsigned long ev = (unsigned long)arg;
 
     if (ev == RECONNECT) {
         spin_lock(&ci->i_ceph_lock);
         ci->i_wanted_max_size = 0;
         ci->i_requested_max_size = 0;
         spin_unlock(&ci->i_ceph_lock);
     } else if (ev == RENEWCAPS) {
         if (cap->cap_gen < atomic_read(&cap->session->s_cap_gen)) {
             /* mds did not re-issue stale cap */
             spin_lock(&ci->i_ceph_lock);
             cap->issued = cap->implemented = CEPH_CAP_PIN;
             spin_unlock(&ci->i_ceph_lock);
         }
     } else if (ev == FORCE_RO) {
     }
     wake_up_all(&ci->i_cap_wq);
     return 0;
 }
 
 static void wake_up_session_caps(struct ceph_mds_session *session, int ev)
 {
     dout("wake_up_session_caps %p mds%d\n", session, session->s_mds);
     ceph_iterate_session_caps(session, wake_up_session_cb,
                   (void *)(unsigned long)ev);
 }
 
 /*
  * Send periodic message to MDS renewing all currently held caps.  The
  * ack will reset the expiration for all caps from this session.
  *
  * caller holds s_mutex
  */
 static int send_renew_caps(struct ceph_mds_client *mdsc,
                struct ceph_mds_session *session)
 {
     struct ceph_msg *msg;
     int state;
 
     if (time_after_eq(jiffies, session->s_cap_ttl) &&
         time_after_eq(session->s_cap_ttl, session->s_renew_requested))
         pr_info("mds%d caps stale\n", session->s_mds);
     session->s_renew_requested = jiffies;
 
     /* do not try to renew caps until a recovering mds has reconnected
      * with its clients. */
     state = ceph_mdsmap_get_state(mdsc->mdsmap, session->s_mds);
     if (state < CEPH_MDS_STATE_RECONNECT) {
         dout("send_renew_caps ignoring mds%d (%s)\n",
              session->s_mds, ceph_mds_state_name(state));
         return 0;
     }
 
     dout("send_renew_caps to mds%d (%s)\n", session->s_mds,
         ceph_mds_state_name(state));
     msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_RENEWCAPS,
                       ++session->s_renew_seq);
     if (!msg)
         return -ENOMEM;
     ceph_con_send(&session->s_con, msg);
     return 0;
 }
 
 static int send_flushmsg_ack(struct ceph_mds_client *mdsc,
                  struct ceph_mds_session *session, u64 seq)
 {
     struct ceph_msg *msg;
 
     dout("send_flushmsg_ack to mds%d (%s)s seq %lld\n",
          session->s_mds, ceph_session_state_name(session->s_state), seq);
     msg = ceph_create_session_msg(CEPH_SESSION_FLUSHMSG_ACK, seq);
     if (!msg)
         return -ENOMEM;
     ceph_con_send(&session->s_con, msg);
     return 0;
 }
 
 
 /*
  * Note new cap ttl, and any transition from stale -> not stale (fresh?).
  *
  * Called under session->s_mutex
  */
 static void renewed_caps(struct ceph_mds_client *mdsc,
              struct ceph_mds_session *session, int is_renew)
 {
     int was_stale;
     int wake = 0;
 
     spin_lock(&session->s_cap_lock);
     was_stale = is_renew && time_after_eq(jiffies, session->s_cap_ttl);
 
     session->s_cap_ttl = session->s_renew_requested +
         mdsc->mdsmap->m_session_timeout*HZ;
 
     if (was_stale) {
         if (time_before(jiffies, session->s_cap_ttl)) {
             pr_info("mds%d caps renewed\n", session->s_mds);
             wake = 1;
         } else {
             pr_info("mds%d caps still stale\n", session->s_mds);
         }
     }
     dout("renewed_caps mds%d ttl now %lu, was %s, now %s\n",
          session->s_mds, session->s_cap_ttl, was_stale ? "stale" : "fresh",
          time_before(jiffies, session->s_cap_ttl) ? "stale" : "fresh");
     spin_unlock(&session->s_cap_lock);
 
     if (wake)
         wake_up_session_caps(session, RENEWCAPS);
 }
 
 /*
  * send a session close request
  */
 static int request_close_session(struct ceph_mds_session *session)
 {
     struct ceph_msg *msg;
 
     dout("request_close_session mds%d state %s seq %lld\n",
          session->s_mds, ceph_session_state_name(session->s_state),
          session->s_seq);
     msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_CLOSE,
                       session->s_seq);
     if (!msg)
         return -ENOMEM;
     ceph_con_send(&session->s_con, msg);
     return 1;
 }
 
 /*
  * Called with s_mutex held.
  */
 static int __close_session(struct ceph_mds_client *mdsc,
              struct ceph_mds_session *session)
 {
     if (session->s_state >= CEPH_MDS_SESSION_CLOSING)
         return 0;
     session->s_state = CEPH_MDS_SESSION_CLOSING;
     return request_close_session(session);
 }
 
 static bool drop_negative_children(struct dentry *dentry)
 {
     struct dentry *child;
     bool all_negative = true;
 
     if (!d_is_dir(dentry))
         goto out;
 
     spin_lock(&dentry->d_lock);
     list_for_each_entry(child, &dentry->d_subdirs, d_child) {
         if (d_really_is_positive(child)) {
             all_negative = false;
             break;
         }
     }
     spin_unlock(&dentry->d_lock);
 
     if (all_negative)
         shrink_dcache_parent(dentry);
 out:
     return all_negative;
 }
 
 /*
  * Trim old(er) caps.
  *
  * Because we can't cache an inode without one or more caps, we do
  * this indirectly: if a cap is unused, we prune its aliases, at which
  * point the inode will hopefully get dropped to.
  *
  * Yes, this is a bit sloppy.  Our only real goal here is to respond to
  * memory pressure from the MDS, though, so it needn't be perfect.
  */
 static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
 {
     int *remaining = arg;
     struct ceph_inode_info *ci = ceph_inode(inode);
     int used, wanted, oissued, mine;
 
     if (*remaining <= 0)
         return -1;
 
     spin_lock(&ci->i_ceph_lock);
     mine = cap->issued | cap->implemented;
     used = __ceph_caps_used(ci);
     wanted = __ceph_caps_file_wanted(ci);
     oissued = __ceph_caps_issued_other(ci, cap);
 
     dout("trim_caps_cb %p cap %p mine %s oissued %s used %s wanted %s\n",
          inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
          ceph_cap_string(used), ceph_cap_string(wanted));
     if (cap == ci->i_auth_cap) {
         if (ci->i_dirty_caps || ci->i_flushing_caps ||
             !list_empty(&ci->i_cap_snaps))
             goto out;
         if ((used | wanted) & CEPH_CAP_ANY_WR)
             goto out;
         /* Note: it's possible that i_filelock_ref becomes non-zero
          * after dropping auth caps. It doesn't hurt because reply
          * of lock mds request will re-add auth caps. */
         if (atomic_read(&ci->i_filelock_ref) > 0)
             goto out;
     }
     /* The inode has cached pages, but it's no longer used.
      * we can safely drop it */
     if (S_ISREG(inode->i_mode) &&
         wanted == 0 && used == CEPH_CAP_FILE_CACHE &&
         !(oissued & CEPH_CAP_FILE_CACHE)) {
       used = 0;
       oissued = 0;
     }
     if ((used | wanted) & ~oissued & mine)
         goto out;   /* we need these caps */
 
     if (oissued) {
         /* we aren't the only cap.. just remove us */
         ceph_remove_cap(cap, true);
         (*remaining)--;
     } else {
         struct dentry *dentry;
         /* try dropping referring dentries */
         spin_unlock(&ci->i_ceph_lock);
         dentry = d_find_any_alias(inode);
         if (dentry && drop_negative_children(dentry)) {
             int count;
             dput(dentry);
             d_prune_aliases(inode);
             count = atomic_read(&inode->i_count);
             if (count == 1)
                 (*remaining)--;
             dout("trim_caps_cb %p cap %p pruned, count now %d\n",
                  inode, cap, count);
         } else {
             dput(dentry);
         }
         return 0;
     }
 
 out:
     spin_unlock(&ci->i_ceph_lock);
     return 0;
 }
 
 /*
  * Trim session cap count down to some max number.
  */
 int ceph_trim_caps(struct ceph_mds_client *mdsc,
            struct ceph_mds_session *session,
            int max_caps)
 {
     int trim_caps = session->s_nr_caps - max_caps;
 
     dout("trim_caps mds%d start: %d / %d, trim %d\n",
          session->s_mds, session->s_nr_caps, max_caps, trim_caps);
     if (trim_caps > 0) {
         int remaining = trim_caps;
 
         ceph_iterate_session_caps(session, trim_caps_cb, &remaining);
         dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
              session->s_mds, session->s_nr_caps, max_caps,
             trim_caps - remaining);
     }
 
     ceph_flush_cap_releases(mdsc, session);
     return 0;
 }
 
 static int check_caps_flush(struct ceph_mds_client *mdsc,
                 u64 want_flush_tid)
 {
     int ret = 1;
 
     spin_lock(&mdsc->cap_dirty_lock);
     if (!list_empty(&mdsc->cap_flush_list)) {
         struct ceph_cap_flush *cf =
             list_first_entry(&mdsc->cap_flush_list,
                      struct ceph_cap_flush, g_list);
         if (cf->tid <= want_flush_tid) {
             dout("check_caps_flush still flushing tid "
                  "%llu <= %llu\n", cf->tid, want_flush_tid);
             ret = 0;
         }
     }
     spin_unlock(&mdsc->cap_dirty_lock);
     return ret;
 }
 
 /*
  * flush all dirty inode data to disk.
  *
  * returns true if we've flushed through want_flush_tid
  */
 static void wait_caps_flush(struct ceph_mds_client *mdsc,
                 u64 want_flush_tid)
 {
     dout("check_caps_flush want %llu\n", want_flush_tid);
 
     wait_event(mdsc->cap_flushing_wq,
            check_caps_flush(mdsc, want_flush_tid));
 
     dout("check_caps_flush ok, flushed thru %llu\n", want_flush_tid);
 }
 
 /*
  * called under s_mutex
  */
 static void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
                    struct ceph_mds_session *session)
 {
     struct ceph_msg *msg = NULL;
     struct ceph_mds_cap_release *head;
     struct ceph_mds_cap_item *item;
     struct ceph_osd_client *osdc = &mdsc->fsc->client->osdc;
     struct ceph_cap *cap;
     LIST_HEAD(tmp_list);
     int num_cap_releases;
     __le32  barrier, *cap_barrier;
 
     down_read(&osdc->lock);
     barrier = cpu_to_le32(osdc->epoch_barrier);
     up_read(&osdc->lock);
 
     spin_lock(&session->s_cap_lock);
 again:
     list_splice_init(&session->s_cap_releases, &tmp_list);
     num_cap_releases = session->s_num_cap_releases;
     session->s_num_cap_releases = 0;
     spin_unlock(&session->s_cap_lock);
 
     while (!list_empty(&tmp_list)) {
         if (!msg) {
             msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE,
                     PAGE_SIZE, GFP_NOFS, false);
             if (!msg)
                 goto out_err;
             head = msg->front.iov_base;
             head->num = cpu_to_le32(0);
             msg->front.iov_len = sizeof(*head);
 
             msg->hdr.version = cpu_to_le16(2);
             msg->hdr.compat_version = cpu_to_le16(1);
         }
 
         cap = list_first_entry(&tmp_list, struct ceph_cap,
                     session_caps);
         list_del(&cap->session_caps);
         num_cap_releases--;
 
         head = msg->front.iov_base;
         put_unaligned_le32(get_unaligned_le32(&head->num) + 1,
                    &head->num);
         item = msg->front.iov_base + msg->front.iov_len;
         item->ino = cpu_to_le64(cap->cap_ino);
         item->cap_id = cpu_to_le64(cap->cap_id);
         item->migrate_seq = cpu_to_le32(cap->mseq);
         item->seq = cpu_to_le32(cap->issue_seq);
         msg->front.iov_len += sizeof(*item);
 
         ceph_put_cap(mdsc, cap);
 
         if (le32_to_cpu(head->num) == CEPH_CAPS_PER_RELEASE) {
             // Append cap_barrier field
             cap_barrier = msg->front.iov_base + msg->front.iov_len;
             *cap_barrier = barrier;
             msg->front.iov_len += sizeof(*cap_barrier);
 
             msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
             dout("send_cap_releases mds%d %p\n", session->s_mds, msg);
             ceph_con_send(&session->s_con, msg);
             msg = NULL;
         }
     }
 
     BUG_ON(num_cap_releases != 0);
 
     spin_lock(&session->s_cap_lock);
     if (!list_empty(&session->s_cap_releases))
         goto again;
     spin_unlock(&session->s_cap_lock);
 
     if (msg) {
         // Append cap_barrier field
         cap_barrier = msg->front.iov_base + msg->front.iov_len;
         *cap_barrier = barrier;
         msg->front.iov_len += sizeof(*cap_barrier);
 
         msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
         dout("send_cap_releases mds%d %p\n", session->s_mds, msg);
         ceph_con_send(&session->s_con, msg);
     }
     return;
 out_err:
     pr_err("send_cap_releases mds%d, failed to allocate message\n",
         session->s_mds);
     spin_lock(&session->s_cap_lock);
     list_splice(&tmp_list, &session->s_cap_releases);
     session->s_num_cap_releases += num_cap_releases;
     spin_unlock(&session->s_cap_lock);
 }
 
 static void ceph_cap_release_work(struct work_struct *work)
 {
     struct ceph_mds_session *session =
         container_of(work, struct ceph_mds_session, s_cap_release_work);
 
     mutex_lock(&session->s_mutex);
     if (session->s_state == CEPH_MDS_SESSION_OPEN ||
         session->s_state == CEPH_MDS_SESSION_HUNG)
         ceph_send_cap_releases(session->s_mdsc, session);
     mutex_unlock(&session->s_mutex);
     ceph_put_mds_session(session);
 }
 
 void ceph_flush_cap_releases(struct ceph_mds_client *mdsc,
                      struct ceph_mds_session *session)
 {
     if (mdsc->stopping)
         return;
 
     ceph_get_mds_session(session);
     if (queue_work(mdsc->fsc->cap_wq,
                &session->s_cap_release_work)) {
         dout("cap release work queued\n");
     } else {
         ceph_put_mds_session(session);
         dout("failed to queue cap release work\n");
     }
 }
 
 /*
  * caller holds session->s_cap_lock
  */
 void __ceph_queue_cap_release(struct ceph_mds_session *session,
                   struct ceph_cap *cap)
 {
     list_add_tail(&cap->session_caps, &session->s_cap_releases);
     session->s_num_cap_releases++;
 
     if (!(session->s_num_cap_releases % CEPH_CAPS_PER_RELEASE))
         ceph_flush_cap_releases(session->s_mdsc, session);
 }
 
 static void ceph_cap_reclaim_work(struct work_struct *work)
 {
     struct ceph_mds_client *mdsc =
         container_of(work, struct ceph_mds_client, cap_reclaim_work);
     int ret = ceph_trim_dentries(mdsc);
     if (ret == -EAGAIN)
         ceph_queue_cap_reclaim_work(mdsc);
 }
 
 void ceph_queue_cap_reclaim_work(struct ceph_mds_client *mdsc)
 {
     if (mdsc->stopping)
         return;
 
         if (queue_work(mdsc->fsc->cap_wq, &mdsc->cap_reclaim_work)) {
                 dout("caps reclaim work queued\n");
         } else {
                 dout("failed to queue caps release work\n");
         }
 }
 
 void ceph_reclaim_caps_nr(struct ceph_mds_client *mdsc, int nr)
 {
     int val;
     if (!nr)
         return;
     val = atomic_add_return(nr, &mdsc->cap_reclaim_pending);
     if ((val % CEPH_CAPS_PER_RELEASE) < nr) {
         atomic_set(&mdsc->cap_reclaim_pending, 0);
         ceph_queue_cap_reclaim_work(mdsc);
     }
 }
 
 /*
  * requests
  */
 
 int ceph_alloc_readdir_reply_buffer(struct ceph_mds_request *req,
                     struct inode *dir)
 {
     struct ceph_inode_info *ci = ceph_inode(dir);
     struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
     struct ceph_mount_options *opt = req->r_mdsc->fsc->mount_options;
     size_t size = sizeof(struct ceph_mds_reply_dir_entry);
     unsigned int num_entries;
     int order;
 
     spin_lock(&ci->i_ceph_lock);
     num_entries = ci->i_files + ci->i_subdirs;
     spin_unlock(&ci->i_ceph_lock);
     num_entries = max(num_entries, 1U);
     num_entries = min(num_entries, opt->max_readdir);
 
     order = get_order(size * num_entries);
     while (order >= 0) {
         rinfo->dir_entries = (void*)__get_free_pages(GFP_KERNEL |
                                  __GFP_NOWARN |
                                  __GFP_ZERO,
                                  order);
         if (rinfo->dir_entries)
             break;
         order--;
     }
     if (!rinfo->dir_entries)
         return -ENOMEM;
 
     num_entries = (PAGE_SIZE << order) / size;
     num_entries = min(num_entries, opt->max_readdir);
 
     rinfo->dir_buf_size = PAGE_SIZE << order;
     req->r_num_caps = num_entries + 1;
     req->r_args.readdir.max_entries = cpu_to_le32(num_entries);
     req->r_args.readdir.max_bytes = cpu_to_le32(opt->max_readdir_bytes);
     return 0;
 }
 
 /*
  * Create an mds request.
  */
 struct ceph_mds_request *
 ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
 {
     struct ceph_mds_request *req;
 
     req = kmem_cache_zalloc(ceph_mds_request_cachep, GFP_NOFS);
     if (!req)
         return ERR_PTR(-ENOMEM);
 
     mutex_init(&req->r_fill_mutex);
     req->r_mdsc = mdsc;
     req->r_started = jiffies;
     req->r_start_latency = ktime_get();
     req->r_resend_mds = -1;
     INIT_LIST_HEAD(&req->r_unsafe_dir_item);
     INIT_LIST_HEAD(&req->r_unsafe_target_item);
     req->r_fmode = -1;
     kref_init(&req->r_kref);
     RB_CLEAR_NODE(&req->r_node);
     INIT_LIST_HEAD(&req->r_wait);
     init_completion(&req->r_completion);
     init_completion(&req->r_safe_completion);
     INIT_LIST_HEAD(&req->r_unsafe_item);
 
     ktime_get_coarse_real_ts64(&req->r_stamp);
 
     req->r_op = op;
     req->r_direct_mode = mode;
     return req;
 }
 
 /*
  * return oldest (lowest) request, tid in request tree, 0 if none.
  *
  * called under mdsc->mutex.
  */
 static struct ceph_mds_request *__get_oldest_req(struct ceph_mds_client *mdsc)
 {
     if (RB_EMPTY_ROOT(&mdsc->request_tree))
         return NULL;
     return rb_entry(rb_first(&mdsc->request_tree),
             struct ceph_mds_request, r_node);
 }
 
 static inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
 {
     return mdsc->oldest_tid;
 }
 
 /*
  * Build a dentry's path.  Allocate on heap; caller must kfree.  Based
  * on build_path_from_dentry in fs/cifs/dir.c.
  *
  * If @stop_on_nosnap, generate path relative to the first non-snapped
  * inode.
  *
  * Encode hidden .snap dirs as a double /, i.e.
  *   foo/.snap/bar -> foo//bar
  */
 char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
                int stop_on_nosnap)
 {
     struct dentry *temp;
     char *path;
     int pos;
     unsigned seq;
     u64 base;
 
     if (!dentry)
         return ERR_PTR(-EINVAL);
 
     path = __getname();
     if (!path)
         return ERR_PTR(-ENOMEM);
 retry:
     pos = PATH_MAX - 1;
     path[pos] = '\0';
 
     seq = read_seqbegin(&rename_lock);
     rcu_read_lock();
     temp = dentry;
     for (;;) {
         struct inode *inode;
 
         spin_lock(&temp->d_lock);
         inode = d_inode(temp);
         if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
             dout("build_path path+%d: %p SNAPDIR\n",
                  pos, temp);
         } else if (stop_on_nosnap && inode && dentry != temp &&
                ceph_snap(inode) == CEPH_NOSNAP) {
             spin_unlock(&temp->d_lock);
             pos++; /* get rid of any prepended '/' */
             break;
         } else {
             pos -= temp->d_name.len;
             if (pos < 0) {
                 spin_unlock(&temp->d_lock);
                 break;
             }
             memcpy(path + pos, temp->d_name.name, temp->d_name.len);
         }
         spin_unlock(&temp->d_lock);
         temp = READ_ONCE(temp->d_parent);
 
         /* Are we at the root? */
         if (IS_ROOT(temp))
             break;
 
         /* Are we out of buffer? */
         if (--pos < 0)
             break;
 
         path[pos] = '/';
     }
     base = ceph_ino(d_inode(temp));
     rcu_read_unlock();
 
     if (read_seqretry(&rename_lock, seq))
         goto retry;
 
     if (pos < 0) {
         /*
          * A rename didn't occur, but somehow we didn't end up where
          * we thought we would. Throw a warning and try again.
          */
         pr_warn("build_path did not end path lookup where "
             "expected, pos is %d\n", pos);
         goto retry;
     }
 
     *pbase = base;
     *plen = PATH_MAX - 1 - pos;
     dout("build_path on %p %d built %llx '%.*s'\n",
          dentry, d_count(dentry), base, *plen, path + pos);
     return path + pos;
 }
 
 static int build_dentry_path(struct dentry *dentry, struct inode *dir,
                  const char **ppath, int *ppathlen, u64 *pino,
                  bool *pfreepath, bool parent_locked)
 {
     char *path;
 
     rcu_read_lock();
     if (!dir)
         dir = d_inode_rcu(dentry->d_parent);
     if (dir && parent_locked && ceph_snap(dir) == CEPH_NOSNAP) {
         *pino = ceph_ino(dir);
         rcu_read_unlock();
         *ppath = dentry->d_name.name;
         *ppathlen = dentry->d_name.len;
         return 0;
     }
     rcu_read_unlock();
     path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
     if (IS_ERR(path))
         return PTR_ERR(path);
     *ppath = path;
     *pfreepath = true;
     return 0;
 }
 
 static int build_inode_path(struct inode *inode,
                 const char **ppath, int *ppathlen, u64 *pino,
                 bool *pfreepath)
 {
     struct dentry *dentry;
     char *path;
 
     if (ceph_snap(inode) == CEPH_NOSNAP) {
         *pino = ceph_ino(inode);
         *ppathlen = 0;
         return 0;
     }
     dentry = d_find_alias(inode);
     path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
     dput(dentry);
     if (IS_ERR(path))
         return PTR_ERR(path);
     *ppath = path;
     *pfreepath = true;
     return 0;
 }
 
 /*
  * request arguments may be specified via an inode *, a dentry *, or
  * an explicit ino+path.
  */
 static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
                   struct inode *rdiri, const char *rpath,
                   u64 rino, const char **ppath, int *pathlen,
                   u64 *ino, bool *freepath, bool parent_locked)
 {
     int r = 0;
 
     if (rinode) {
         r = build_inode_path(rinode, ppath, pathlen, ino, freepath);
         dout(" inode %p %llx.%llx\n", rinode, ceph_ino(rinode),
              ceph_snap(rinode));
     } else if (rdentry) {
         r = build_dentry_path(rdentry, rdiri, ppath, pathlen, ino,
                     freepath, parent_locked);
         dout(" dentry %p %llx/%.*s\n", rdentry, *ino, *pathlen,
              *ppath);
     } else if (rpath || rino) {
         *ino = rino;
         *ppath = rpath;
         *pathlen = rpath ? strlen(rpath) : 0;
         dout(" path %.*s\n", *pathlen, rpath);
     }
 
     return r;
 }
 
 static void encode_timestamp_and_gids(void **p,
                       const struct ceph_mds_request *req)
 {
     struct ceph_timespec ts;
     int i;
 
     ceph_encode_timespec64(&ts, &req->r_stamp);
     ceph_encode_copy(p, &ts, sizeof(ts));
 
     /* gid_list */
     ceph_encode_32(p, req->r_cred->group_info->ngroups);
     for (i = 0; i < req->r_cred->group_info->ngroups; i++)
         ceph_encode_64(p, from_kgid(&init_user_ns,
                         req->r_cred->group_info->gid[i]));
 }
 
 /*
  * called under mdsc->mutex
  */
 static struct ceph_msg *create_request_message(struct ceph_mds_session *session,
                            struct ceph_mds_request *req,
                            bool drop_cap_releases)
 {
     int mds = session->s_mds;
     struct ceph_mds_client *mdsc = session->s_mdsc;
     struct ceph_msg *msg;
     struct ceph_mds_request_head_old *head;
     const char *path1 = NULL;
     const char *path2 = NULL;
     u64 ino1 = 0, ino2 = 0;
     int pathlen1 = 0, pathlen2 = 0;
     bool freepath1 = false, freepath2 = false;
     int len;
     u16 releases;
     void *p, *end;
     int ret;
     bool legacy = !(session->s_con.peer_features & CEPH_FEATURE_FS_BTIME);
 
     ret = set_request_path_attr(req->r_inode, req->r_dentry,
                   req->r_parent, req->r_path1, req->r_ino1.ino,
                   &path1, &pathlen1, &ino1, &freepath1,
                   test_bit(CEPH_MDS_R_PARENT_LOCKED,
                     &req->r_req_flags));
     if (ret < 0) {
         msg = ERR_PTR(ret);
         goto out;
     }
 
     /* If r_old_dentry is set, then assume that its parent is locked */
     ret = set_request_path_attr(NULL, req->r_old_dentry,
                   req->r_old_dentry_dir,
                   req->r_path2, req->r_ino2.ino,
                   &path2, &pathlen2, &ino2, &freepath2, true);
     if (ret < 0) {
         msg = ERR_PTR(ret);
         goto out_free1;
     }
 
     len = legacy ? sizeof(*head) : sizeof(struct ceph_mds_request_head);
     len += pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64)) +
         sizeof(struct ceph_timespec);
     len += sizeof(u32) + (sizeof(u64) * req->r_cred->group_info->ngroups);
 
     /* calculate (max) length for cap releases */
     len += sizeof(struct ceph_mds_request_release) *
         (!!req->r_inode_drop + !!req->r_dentry_drop +
          !!req->r_old_inode_drop + !!req->r_old_dentry_drop);
 
     if (req->r_dentry_drop)
         len += pathlen1;
     if (req->r_old_dentry_drop)
         len += pathlen2;
 
     msg = ceph_msg_new2(CEPH_MSG_CLIENT_REQUEST, len, 1, GFP_NOFS, false);
     if (!msg) {
         msg = ERR_PTR(-ENOMEM);
         goto out_free2;
     }
 
     msg->hdr.tid = cpu_to_le64(req->r_tid);
 
     /*
      * The old ceph_mds_request_head didn't contain a version field, and
      * one was added when we moved the message version from 3->4.
      */
     if (legacy) {
         msg->hdr.version = cpu_to_le16(3);
         head = msg->front.iov_base;
         p = msg->front.iov_base + sizeof(*head);
     } else {
         struct ceph_mds_request_head *new_head = msg->front.iov_base;
 
         msg->hdr.version = cpu_to_le16(4);
         new_head->version = cpu_to_le16(CEPH_MDS_REQUEST_HEAD_VERSION);
         head = (struct ceph_mds_request_head_old *)&new_head->oldest_client_tid;
         p = msg->front.iov_base + sizeof(*new_head);
     }
 
     end = msg->front.iov_base + msg->front.iov_len;
 
     head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
     head->op = cpu_to_le32(req->r_op);
     head->caller_uid = cpu_to_le32(from_kuid(&init_user_ns,
                          req->r_cred->fsuid));
     head->caller_gid = cpu_to_le32(from_kgid(&init_user_ns,
                          req->r_cred->fsgid));
     head->ino = cpu_to_le64(req->r_deleg_ino);
     head->args = req->r_args;
 
     ceph_encode_filepath(&p, end, ino1, path1);
     ceph_encode_filepath(&p, end, ino2, path2);
 
     /* make note of release offset, in case we need to replay */
     req->r_request_release_offset = p - msg->front.iov_base;
 
     /* cap releases */
     releases = 0;
     if (req->r_inode_drop)
         releases += ceph_encode_inode_release(&p,
               req->r_inode ? req->r_inode : d_inode(req->r_dentry),
               mds, req->r_inode_drop, req->r_inode_unless,
               req->r_op == CEPH_MDS_OP_READDIR);
     if (req->r_dentry_drop)
         releases += ceph_encode_dentry_release(&p, req->r_dentry,
                 req->r_parent, mds, req->r_dentry_drop,
                 req->r_dentry_unless);
     if (req->r_old_dentry_drop)
         releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
                 req->r_old_dentry_dir, mds,
                 req->r_old_dentry_drop,
                 req->r_old_dentry_unless);
     if (req->r_old_inode_drop)
         releases += ceph_encode_inode_release(&p,
               d_inode(req->r_old_dentry),
               mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
 
     if (drop_cap_releases) {
         releases = 0;
         p = msg->front.iov_base + req->r_request_release_offset;
     }
 
     head->num_releases = cpu_to_le16(releases);
 
     encode_timestamp_and_gids(&p, req);
 
     if (WARN_ON_ONCE(p > end)) {
         ceph_msg_put(msg);
         msg = ERR_PTR(-ERANGE);
         goto out_free2;
     }
 
     msg->front.iov_len = p - msg->front.iov_base;
     msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
 
     if (req->r_pagelist) {
         struct ceph_pagelist *pagelist = req->r_pagelist;
         ceph_msg_data_add_pagelist(msg, pagelist);
         msg->hdr.data_len = cpu_to_le32(pagelist->length);
     } else {
         msg->hdr.data_len = 0;
     }
 
     msg->hdr.data_off = cpu_to_le16(0);
 
 out_free2:
     if (freepath2)
         ceph_mdsc_free_path((char *)path2, pathlen2);
 out_free1:
     if (freepath1)
         ceph_mdsc_free_path((char *)path1, pathlen1);
 out:
     return msg;
 }
 
 /*
  * called under mdsc->mutex if error, under no mutex if
  * success.
  */
 static void complete_request(struct ceph_mds_client *mdsc,
                  struct ceph_mds_request *req)
 {
     req->r_end_latency = ktime_get();
 
     if (req->r_callback)
         req->r_callback(mdsc, req);
     complete_all(&req->r_completion);
 }
 
 static struct ceph_mds_request_head_old *
 find_old_request_head(void *p, u64 features)
 {
     bool legacy = !(features & CEPH_FEATURE_FS_BTIME);
     struct ceph_mds_request_head *new_head;
 
     if (legacy)
         return (struct ceph_mds_request_head_old *)p;
     new_head = (struct ceph_mds_request_head *)p;
     return (struct ceph_mds_request_head_old *)&new_head->oldest_client_tid;
 }
 
 /*
  * called under mdsc->mutex
  */
 static int __prepare_send_request(struct ceph_mds_session *session,
                   struct ceph_mds_request *req,
                   bool drop_cap_releases)
 {
     int mds = session->s_mds;
     struct ceph_mds_client *mdsc = session->s_mdsc;
     struct ceph_mds_request_head_old *rhead;
     struct ceph_msg *msg;
     int flags = 0, max_retry;
 
     /*
      * The type of 'r_attempts' in kernel 'ceph_mds_request'
      * is 'int', while in 'ceph_mds_request_head' the type of
      * 'num_retry' is '__u8'. So in case the request retries
      *  exceeding 256 times, the MDS will receive a incorrect
      *  retry seq.
      *
      * In this case it's ususally a bug in MDS and continue
      * retrying the request makes no sense.
      *
      * In future this could be fixed in ceph code, so avoid
      * using the hardcode here.
      */
     max_retry = sizeof_field(struct ceph_mds_request_head, num_retry);
     max_retry = 1 << (max_retry * BITS_PER_BYTE);
     if (req->r_attempts >= max_retry) {
         pr_warn_ratelimited("%s request tid %llu seq overflow\n",
                     __func__, req->r_tid);
         return -EMULTIHOP;
     }
 
     req->r_attempts++;
     if (req->r_inode) {
         struct ceph_cap *cap =
             ceph_get_cap_for_mds(ceph_inode(req->r_inode), mds);
 
         if (cap)
             req->r_sent_on_mseq = cap->mseq;
         else
             req->r_sent_on_mseq = -1;
     }
     dout("%s %p tid %lld %s (attempt %d)\n", __func__, req,
          req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);
 
     if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
         void *p;
 
         /*
          * Replay.  Do not regenerate message (and rebuild
          * paths, etc.); just use the original message.
          * Rebuilding paths will break for renames because
          * d_move mangles the src name.
          */
         msg = req->r_request;
         rhead = find_old_request_head(msg->front.iov_base,
                           session->s_con.peer_features);
 
         flags = le32_to_cpu(rhead->flags);
         flags |= CEPH_MDS_FLAG_REPLAY;
         rhead->flags = cpu_to_le32(flags);
 
         if (req->r_target_inode)
             rhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));
 
         rhead->num_retry = req->r_attempts - 1;
 
         /* remove cap/dentry releases from message */
         rhead->num_releases = 0;
 
         p = msg->front.iov_base + req->r_request_release_offset;
         encode_timestamp_and_gids(&p, req);
 
         msg->front.iov_len = p - msg->front.iov_base;
         msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
         return 0;
     }
 
     if (req->r_request) {
         ceph_msg_put(req->r_request);
         req->r_request = NULL;
     }
     msg = create_request_message(session, req, drop_cap_releases);
     if (IS_ERR(msg)) {
         req->r_err = PTR_ERR(msg);
         return PTR_ERR(msg);
     }
     req->r_request = msg;
 
     rhead = find_old_request_head(msg->front.iov_base,
                       session->s_con.peer_features);
     rhead->oldest_client_tid = cpu_to_le64(__get_oldest_tid(mdsc));
     if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
         flags |= CEPH_MDS_FLAG_REPLAY;
     if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags))
         flags |= CEPH_MDS_FLAG_ASYNC;
     if (req->r_parent)
         flags |= CEPH_MDS_FLAG_WANT_DENTRY;
     rhead->flags = cpu_to_le32(flags);
     rhead->num_fwd = req->r_num_fwd;
     rhead->num_retry = req->r_attempts - 1;
 
     dout(" r_parent = %p\n", req->r_parent);
     return 0;
 }
 
 /*
  * called under mdsc->mutex
  */
 static int __send_request(struct ceph_mds_session *session,
               struct ceph_mds_request *req,
               bool drop_cap_releases)
 {
     int err;
 
     err = __prepare_send_request(session, req, drop_cap_releases);
     if (!err) {
         ceph_msg_get(req->r_request);
         ceph_con_send(&session->s_con, req->r_request);
     }
 
     return err;
 }
 
 /*
  * send request, or put it on the appropriate wait list.
  */
 static void __do_request(struct ceph_mds_client *mdsc,
             struct ceph_mds_request *req)
 {
     struct ceph_mds_session *session = NULL;
     int mds = -1;
     int err = 0;
     bool random;
 
     if (req->r_err || test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
         if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
             __unregister_request(mdsc, req);
         return;
     }
 
     if (req->r_timeout &&
         time_after_eq(jiffies, req->r_started + req->r_timeout)) {
         dout("do_request timed out\n");
         err = -ETIMEDOUT;
         goto finish;
     }
     if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
         dout("do_request forced umount\n");
         err = -EIO;
         goto finish;
     }
     if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_MOUNTING) {
         if (mdsc->mdsmap_err) {
             err = mdsc->mdsmap_err;
             dout("do_request mdsmap err %d\n", err);
             goto finish;
         }
         if (mdsc->mdsmap->m_epoch == 0) {
             dout("do_request no mdsmap, waiting for map\n");
             list_add(&req->r_wait, &mdsc->waiting_for_map);
             return;
         }
         if (!(mdsc->fsc->mount_options->flags &
               CEPH_MOUNT_OPT_MOUNTWAIT) &&
             !ceph_mdsmap_is_cluster_available(mdsc->mdsmap)) {
             err = -EHOSTUNREACH;
             goto finish;
         }
     }
 
     put_request_session(req);
 
     mds = __choose_mds(mdsc, req, &random);
     if (mds < 0 ||
         ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
         if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags)) {
             err = -EJUKEBOX;
             goto finish;
         }
         dout("do_request no mds or not active, waiting for map\n");
         list_add(&req->r_wait, &mdsc->waiting_for_map);
         return;
     }
 
     /* get, open session */
     session = __ceph_lookup_mds_session(mdsc, mds);
     if (!session) {
         session = register_session(mdsc, mds);
         if (IS_ERR(session)) {
             err = PTR_ERR(session);
             goto finish;
         }
     }
     req->r_session = ceph_get_mds_session(session);
 
     dout("do_request mds%d session %p state %s\n", mds, session,
          ceph_session_state_name(session->s_state));
     if (session->s_state != CEPH_MDS_SESSION_OPEN &&
         session->s_state != CEPH_MDS_SESSION_HUNG) {
         /*
          * We cannot queue async requests since the caps and delegated
          * inodes are bound to the session. Just return -EJUKEBOX and
          * let the caller retry a sync request in that case.
          */
         if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags)) {
             err = -EJUKEBOX;
             goto out_session;
         }
 
         /*
          * If the session has been REJECTED, then return a hard error,
          * unless it's a CLEANRECOVER mount, in which case we'll queue
          * it to the mdsc queue.
          */
         if (session->s_state == CEPH_MDS_SESSION_REJECTED) {
             if (ceph_test_mount_opt(mdsc->fsc, CLEANRECOVER))
                 list_add(&req->r_wait, &mdsc->waiting_for_map);
             else
                 err = -EACCES;
             goto out_session;
         }
 
         if (session->s_state == CEPH_MDS_SESSION_NEW ||
             session->s_state == CEPH_MDS_SESSION_CLOSING) {
             err = __open_session(mdsc, session);
             if (err)
                 goto out_session;
             /* retry the same mds later */
             if (random)
                 req->r_resend_mds = mds;
         }
         list_add(&req->r_wait, &session->s_waiting);
         goto out_session;
     }
 
     /* send request */
     req->r_resend_mds = -1;   /* forget any previous mds hint */
 
     if (req->r_request_started == 0)   /* note request start time */
         req->r_request_started = jiffies;
 
     /*
      * For async create we will choose the auth MDS of frag in parent
      * directory to send the request and ususally this works fine, but
      * if the migrated the dirtory to another MDS before it could handle
      * it the request will be forwarded.
      *
      * And then the auth cap will be changed.
      */
     if (test_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags) && req->r_num_fwd) {
         struct ceph_dentry_info *di = ceph_dentry(req->r_dentry);
         struct ceph_inode_info *ci;
         struct ceph_cap *cap;
 
         /*
          * The request maybe handled very fast and the new inode
          * hasn't been linked to the dentry yet. We need to wait
          * for the ceph_finish_async_create(), which shouldn't be
          * stuck too long or fail in thoery, to finish when forwarding
          * the request.
          */
         if (!d_inode(req->r_dentry)) {
             err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_CREATE_BIT,
                       TASK_KILLABLE);
             if (err) {
                 mutex_lock(&req->r_fill_mutex);
                 set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
                 mutex_unlock(&req->r_fill_mutex);
                 goto out_session;
             }
         }
 
         ci = ceph_inode(d_inode(req->r_dentry));
 
         spin_lock(&ci->i_ceph_lock);
         cap = ci->i_auth_cap;
         if (ci->i_ceph_flags & CEPH_I_ASYNC_CREATE && mds != cap->mds) {
             dout("do_request session changed for auth cap %d -> %d\n",
                  cap->session->s_mds, session->s_mds);
 
             /* Remove the auth cap from old session */
             spin_lock(&cap->session->s_cap_lock);
             cap->session->s_nr_caps--;
             list_del_init(&cap->session_caps);
             spin_unlock(&cap->session->s_cap_lock);
 
             /* Add the auth cap to the new session */
             cap->mds = mds;
             cap->session = session;
             spin_lock(&session->s_cap_lock);
             session->s_nr_caps++;
             list_add_tail(&cap->session_caps, &session->s_caps);
             spin_unlock(&session->s_cap_lock);
 
             change_auth_cap_ses(ci, session);
         }
         spin_unlock(&ci->i_ceph_lock);
     }
 
     err = __send_request(session, req, false);
 
 out_session:
     ceph_put_mds_session(session);
 finish:
     if (err) {
         dout("__do_request early error %d\n", err);
         req->r_err = err;
         complete_request(mdsc, req);
         __unregister_request(mdsc, req);
     }
     return;
 }
 
 /*
  * called under mdsc->mutex
  */
 static void __wake_requests(struct ceph_mds_client *mdsc,
                 struct list_head *head)
 {
     struct ceph_mds_request *req;
     LIST_HEAD(tmp_list);
 
     list_splice_init(head, &tmp_list);
 
     while (!list_empty(&tmp_list)) {
         req = list_entry(tmp_list.next,
                  struct ceph_mds_request, r_wait);
         list_del_init(&req->r_wait);
         dout(" wake request %p tid %llu\n", req, req->r_tid);
         __do_request(mdsc, req);
     }
 }
 
 /*
  * Wake up threads with requests pending for @mds, so that they can
  * resubmit their requests to a possibly different mds.
  */
 static void kick_requests(struct ceph_mds_client *mdsc, int mds)
 {
     struct ceph_mds_request *req;
     struct rb_node *p = rb_first(&mdsc->request_tree);
 
     dout("kick_requests mds%d\n", mds);
     while (p) {
         req = rb_entry(p, struct ceph_mds_request, r_node);
         p = rb_next(p);
         if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
             continue;
         if (req->r_attempts > 0)
             continue; /* only new requests */
         if (req->r_session &&
             req->r_session->s_mds == mds) {
             dout(" kicking tid %llu\n", req->r_tid);
             list_del_init(&req->r_wait);
             __do_request(mdsc, req);
         }
     }
 }
 
 int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir,
                   struct ceph_mds_request *req)
 {
     int err = 0;
 
     /* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */
     if (req->r_inode)
         ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
     if (req->r_parent) {
         struct ceph_inode_info *ci = ceph_inode(req->r_parent);
         int fmode = (req->r_op & CEPH_MDS_OP_WRITE) ?
                 CEPH_FILE_MODE_WR : CEPH_FILE_MODE_RD;
         spin_lock(&ci->i_ceph_lock);
         ceph_take_cap_refs(ci, CEPH_CAP_PIN, false);
         __ceph_touch_fmode(ci, mdsc, fmode);
         spin_unlock(&ci->i_ceph_lock);
     }
     if (req->r_old_dentry_dir)
         ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
                   CEPH_CAP_PIN);
 
     if (req->r_inode) {
         err = ceph_wait_on_async_create(req->r_inode);
         if (err) {
             dout("%s: wait for async create returned: %d\n",
                  __func__, err);
             return err;
         }
     }
 
     if (!err && req->r_old_inode) {
         err = ceph_wait_on_async_create(req->r_old_inode);
         if (err) {
             dout("%s: wait for async create returned: %d\n",
                  __func__, err);
             return err;
         }
     }
 
     dout("submit_request on %p for inode %p\n", req, dir);
     mutex_lock(&mdsc->mutex);
     __register_request(mdsc, req, dir);
     __do_request(mdsc, req);
     err = req->r_err;
     mutex_unlock(&mdsc->mutex);
     return err;
 }
 
 int ceph_mdsc_wait_request(struct ceph_mds_client *mdsc,
                struct ceph_mds_request *req,
                ceph_mds_request_wait_callback_t wait_func)
 {
     int err;
 
     /* wait */
     dout("do_request waiting\n");
     if (wait_func) {
         err = wait_func(mdsc, req);
     } else {
         long timeleft = wait_for_completion_killable_timeout(
                     &req->r_completion,
                     ceph_timeout_jiffies(req->r_timeout));
         if (timeleft > 0)
             err = 0;
         else if (!timeleft)
             err = -ETIMEDOUT;  /* timed out */
         else
             err = timeleft;  /* killed */
     }
     dout("do_request waited, got %d\n", err);
     mutex_lock(&mdsc->mutex);
 
     /* only abort if we didn't race with a real reply */
     if (test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags)) {
         err = le32_to_cpu(req->r_reply_info.head->result);
     } else if (err < 0) {
         dout("aborted request %lld with %d\n", req->r_tid, err);
 
         /*
          * ensure we aren't running concurrently with
          * ceph_fill_trace or ceph_readdir_prepopulate, which
          * rely on locks (dir mutex) held by our caller.
          */
         mutex_lock(&req->r_fill_mutex);
         req->r_err = err;
         set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
         mutex_unlock(&req->r_fill_mutex);
 
         if (req->r_parent &&
             (req->r_op & CEPH_MDS_OP_WRITE))
             ceph_invalidate_dir_request(req);
     } else {
         err = req->r_err;
     }
 
     mutex_unlock(&mdsc->mutex);
     return err;
 }
 
 /*
  * Synchrously perform an mds request.  Take care of all of the
  * session setup, forwarding, retry details.
  */
 int ceph_mdsc_do_request(struct ceph_mds_client *mdsc,
              struct inode *dir,
              struct ceph_mds_request *req)
 {
     int err;
 
     dout("do_request on %p\n", req);
 
     /* issue */
     err = ceph_mdsc_submit_request(mdsc, dir, req);
     if (!err)
         err = ceph_mdsc_wait_request(mdsc, req, NULL);
     dout("do_request %p done, result %d\n", req, err);
     return err;
 }
 
 /*
  * Invalidate dir's completeness, dentry lease state on an aborted MDS
  * namespace request.
  */
 void ceph_invalidate_dir_request(struct ceph_mds_request *req)
 {
     struct inode *dir = req->r_parent;
     struct inode *old_dir = req->r_old_dentry_dir;
 
     dout("invalidate_dir_request %p %p (complete, lease(s))\n", dir, old_dir);
 
     ceph_dir_clear_complete(dir);
     if (old_dir)
         ceph_dir_clear_complete(old_dir);
     if (req->r_dentry)
         ceph_invalidate_dentry_lease(req->r_dentry);
     if (req->r_old_dentry)
         ceph_invalidate_dentry_lease(req->r_old_dentry);
 }
 
 /*
  * Handle mds reply.
  *
  * We take the session mutex and parse and process the reply immediately.
  * This preserves the logical ordering of replies, capabilities, etc., sent
  * by the MDS as they are applied to our local cache.
  */
 static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
 {
     struct ceph_mds_client *mdsc = session->s_mdsc;
     struct ceph_mds_request *req;
     struct ceph_mds_reply_head *head = msg->front.iov_base;
     struct ceph_mds_reply_info_parsed *rinfo;  /* parsed reply info */
     struct ceph_snap_realm *realm;
     u64 tid;
     int err, result;
     int mds = session->s_mds;
 
     if (msg->front.iov_len < sizeof(*head)) {
         pr_err("mdsc_handle_reply got corrupt (short) reply\n");
         ceph_msg_dump(msg);
         return;
     }
 
     /* get request, session */
     tid = le64_to_cpu(msg->hdr.tid);
     mutex_lock(&mdsc->mutex);
     req = lookup_get_request(mdsc, tid);
     if (!req) {
         dout("handle_reply on unknown tid %llu\n", tid);
         mutex_unlock(&mdsc->mutex);
         return;
     }
     dout("handle_reply %p\n", req);
 
     /* correct session? */
     if (req->r_session != session) {
         pr_err("mdsc_handle_reply got %llu on session mds%d"
                " not mds%d\n", tid, session->s_mds,
                req->r_session ? req->r_session->s_mds : -1);
         mutex_unlock(&mdsc->mutex);
         goto out;
     }
 
     /* dup? */
     if ((test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags) && !head->safe) ||
         (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags) && head->safe)) {
         pr_warn("got a dup %s reply on %llu from mds%d\n",
                head->safe ? "safe" : "unsafe", tid, mds);
         mutex_unlock(&mdsc->mutex);
         goto out;
     }
     if (test_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags)) {
         pr_warn("got unsafe after safe on %llu from mds%d\n",
                tid, mds);
         mutex_unlock(&mdsc->mutex);
         goto out;
     }
 
     result = le32_to_cpu(head->result);
 
     if (head->safe) {
         set_bit(CEPH_MDS_R_GOT_SAFE, &req->r_req_flags);
         __unregister_request(mdsc, req);
 
         /* last request during umount? */
         if (mdsc->stopping && !__get_oldest_req(mdsc))
             complete_all(&mdsc->safe_umount_waiters);
 
         if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
             /*
              * We already handled the unsafe response, now do the
              * cleanup.  No need to examine the response; the MDS
              * doesn't include any result info in the safe
              * response.  And even if it did, there is nothing
              * useful we could do with a revised return value.
              */
             dout("got safe reply %llu, mds%d\n", tid, mds);
 
             mutex_unlock(&mdsc->mutex);
             goto out;
         }
     } else {
         set_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags);
         list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
     }
 
     dout("handle_reply tid %lld result %d\n", tid, result);
     rinfo = &req->r_reply_info;
     if (test_bit(CEPHFS_FEATURE_REPLY_ENCODING, &session->s_features))
         err = parse_reply_info(session, msg, rinfo, (u64)-1);
     else
         err = parse_reply_info(session, msg, rinfo, session->s_con.peer_features);
     mutex_unlock(&mdsc->mutex);
 
     /* Must find target inode outside of mutexes to avoid deadlocks */
     if ((err >= 0) && rinfo->head->is_target) {
         struct inode *in;
         struct ceph_vino tvino = {
             .ino  = le64_to_cpu(rinfo->targeti.in->ino),
             .snap = le64_to_cpu(rinfo->targeti.in->snapid)
         };
 
         in = ceph_get_inode(mdsc->fsc->sb, tvino);
         if (IS_ERR(in)) {
             err = PTR_ERR(in);
             mutex_lock(&session->s_mutex);
             goto out_err;
         }
         req->r_target_inode = in;
     }
 
     mutex_lock(&session->s_mutex);
     if (err < 0) {
         pr_err("mdsc_handle_reply got corrupt reply mds%d(tid:%lld)\n", mds, tid);
         ceph_msg_dump(msg);
         goto out_err;
     }
 
     /* snap trace */
     realm = NULL;
     if (rinfo->snapblob_len) {
         down_write(&mdsc->snap_rwsem);
         ceph_update_snap_trace(mdsc, rinfo->snapblob,
                 rinfo->snapblob + rinfo->snapblob_len,
                 le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP,
                 &realm);
         downgrade_write(&mdsc->snap_rwsem);
     } else {
         down_read(&mdsc->snap_rwsem);
     }
 
     /* insert trace into our cache */
     mutex_lock(&req->r_fill_mutex);
     current->journal_info = req;
     err = ceph_fill_trace(mdsc->fsc->sb, req);
     if (err == 0) {
         if (result == 0 && (req->r_op == CEPH_MDS_OP_READDIR ||
                     req->r_op == CEPH_MDS_OP_LSSNAP))
             ceph_readdir_prepopulate(req, req->r_session);
     }
     current->journal_info = NULL;
     mutex_unlock(&req->r_fill_mutex);
 
     up_read(&mdsc->snap_rwsem);
     if (realm)
         ceph_put_snap_realm(mdsc, realm);
 
     if (err == 0) {
         if (req->r_target_inode &&
             test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags)) {
             struct ceph_inode_info *ci =
                 ceph_inode(req->r_target_inode);
             spin_lock(&ci->i_unsafe_lock);
             list_add_tail(&req->r_unsafe_target_item,
                       &ci->i_unsafe_iops);
             spin_unlock(&ci->i_unsafe_lock);
         }
 
         ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
     }
 out_err:
     mutex_lock(&mdsc->mutex);
     if (!test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
         if (err) {
             req->r_err = err;
         } else {
             req->r_reply =  ceph_msg_get(msg);
             set_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags);
         }
     } else {
         dout("reply arrived after request %lld was aborted\n", tid);
     }
     mutex_unlock(&mdsc->mutex);
 
     mutex_unlock(&session->s_mutex);
 
     /* kick calling process */
     complete_request(mdsc, req);
 
     ceph_update_metadata_metrics(&mdsc->metric, req->r_start_latency,
                      req->r_end_latency, err);
 out:
     ceph_mdsc_put_request(req);
     return;
 }
 
 
 
 /*
  * handle mds notification that our request has been forwarded.
  */
 static void handle_forward(struct ceph_mds_client *mdsc,
                struct ceph_mds_session *session,
                struct ceph_msg *msg)
 {
     struct ceph_mds_request *req;
     u64 tid = le64_to_cpu(msg->hdr.tid);
     u32 next_mds;
     u32 fwd_seq;
     int err = -EINVAL;
     void *p = msg->front.iov_base;
     void *end = p + msg->front.iov_len;
     bool aborted = false;
 
     ceph_decode_need(&p, end, 2*sizeof(u32), bad);
     next_mds = ceph_decode_32(&p);
     fwd_seq = ceph_decode_32(&p);
 
     mutex_lock(&mdsc->mutex);
     req = lookup_get_request(mdsc, tid);
     if (!req) {
         mutex_unlock(&mdsc->mutex);
         dout("forward tid %llu to mds%d - req dne\n", tid, next_mds);
         return;  /* dup reply? */
     }
 
     if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {
         dout("forward tid %llu aborted, unregistering\n", tid);
         __unregister_request(mdsc, req);
     } else if (fwd_seq <= req->r_num_fwd) {
         /*
          * The type of 'num_fwd' in ceph 'MClientRequestForward'
          * is 'int32_t', while in 'ceph_mds_request_head' the
          * type is '__u8'. So in case the request bounces between
          * MDSes exceeding 256 times, the client will get stuck.
          *
          * In this case it's ususally a bug in MDS and continue
          * bouncing the request makes no sense.
          *
          * In future this could be fixed in ceph code, so avoid
          * using the hardcode here.
          */
         int max = sizeof_field(struct ceph_mds_request_head, num_fwd);
         max = 1 << (max * BITS_PER_BYTE);
         if (req->r_num_fwd >= max) {
             mutex_lock(&req->r_fill_mutex);
             req->r_err = -EMULTIHOP;
             set_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags);
             mutex_unlock(&req->r_fill_mutex);
             aborted = true;
             pr_warn_ratelimited("forward tid %llu seq overflow\n",
                         tid);
         } else {
             dout("forward tid %llu to mds%d - old seq %d <= %d\n",
                  tid, next_mds, req->r_num_fwd, fwd_seq);
         }
     } else {
         /* resend. forward race not possible; mds would drop */
         dout("forward tid %llu to mds%d (we resend)\n", tid, next_mds);
         BUG_ON(req->r_err);
         BUG_ON(test_bit(CEPH_MDS_R_GOT_RESULT, &req->r_req_flags));
         req->r_attempts = 0;
         req->r_num_fwd = fwd_seq;
         req->r_resend_mds = next_mds;
         put_request_session(req);
         __do_request(mdsc, req);
     }
     mutex_unlock(&mdsc->mutex);
 
     /* kick calling process */
     if (aborted)
         complete_request(mdsc, req);
     ceph_mdsc_put_request(req);
     return;
 
 bad:
     pr_err("mdsc_handle_forward decode error err=%d\n", err);
 }
 
 static int __decode_session_metadata(void **p, void *end,
                      bool *blocklisted)
 {
     /* map<string,string> */
     u32 n;
     bool err_str;
     ceph_decode_32_safe(p, end, n, bad);
     while (n-- > 0) {
         u32 len;
         ceph_decode_32_safe(p, end, len, bad);
         ceph_decode_need(p, end, len, bad);
         err_str = !strncmp(*p, "error_string", len);
         *p += len;
         ceph_decode_32_safe(p, end, len, bad);
         ceph_decode_need(p, end, len, bad);
         /*
          * Match "blocklisted (blacklisted)" from newer MDSes,
          * or "blacklisted" from older MDSes.
          */
         if (err_str && strnstr(*p, "blacklisted", len))
             *blocklisted = true;
         *p += len;
     }
     return 0;
 bad:
     return -1;
 }
 
 /*
  * handle a mds session control message
  */
 static void handle_session(struct ceph_mds_session *session,
                struct ceph_msg *msg)
 {
     struct ceph_mds_client *mdsc = session->s_mdsc;
     int mds = session->s_mds;
     int msg_version = le16_to_cpu(msg->hdr.version);
     void *p = msg->front.iov_base;
     void *end = p + msg->front.iov_len;
     struct ceph_mds_session_head *h;
     u32 op;
     u64 seq, features = 0;
     int wake = 0;
     bool blocklisted = false;
 
     /* decode */
     ceph_decode_need(&p, end, sizeof(*h), bad);
     h = p;
     p += sizeof(*h);
 
     op = le32_to_cpu(h->op);
     seq = le64_to_cpu(h->seq);
 
     if (msg_version >= 3) {
         u32 len;
         /* version >= 2 and < 5, decode metadata, skip otherwise
          * as it's handled via flags.
          */
         if (msg_version >= 5)
             ceph_decode_skip_map(&p, end, string, string, bad);
         else if (__decode_session_metadata(&p, end, &blocklisted) < 0)
             goto bad;
 
         /* version >= 3, feature bits */
         ceph_decode_32_safe(&p, end, len, bad);
         if (len) {
             ceph_decode_64_safe(&p, end, features, bad);
             p += len - sizeof(features);
         }
     }
 
     if (msg_version >= 5) {
         u32 flags, len;
 
         /* version >= 4 */
         ceph_decode_skip_16(&p, end, bad); /* struct_v, struct_cv */
         ceph_decode_32_safe(&p, end, len, bad); /* len */
         ceph_decode_skip_n(&p, end, len, bad); /* metric_spec */
 
         /* version >= 5, flags   */
         ceph_decode_32_safe(&p, end, flags, bad);
         if (flags & CEPH_SESSION_BLOCKLISTED) {
             pr_warn("mds%d session blocklisted\n", session->s_mds);
             blocklisted = true;
         }
     }
 
     mutex_lock(&mdsc->mutex);
     if (op == CEPH_SESSION_CLOSE) {
         ceph_get_mds_session(session);
         __unregister_session(mdsc, session);
     }
     /* FIXME: this ttl calculation is generous */
     session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose;
     mutex_unlock(&mdsc->mutex);
 
     mutex_lock(&session->s_mutex);
 
     dout("handle_session mds%d %s %p state %s seq %llu\n",
          mds, ceph_session_op_name(op), session,
          ceph_session_state_name(session->s_state), seq);
 
     if (session->s_state == CEPH_MDS_SESSION_HUNG) {
         session->s_state = CEPH_MDS_SESSION_OPEN;
         pr_info("mds%d came back\n", session->s_mds);
     }
 
     switch (op) {
     case CEPH_SESSION_OPEN:
         if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
             pr_info("mds%d reconnect success\n", session->s_mds);
 
         if (session->s_state == CEPH_MDS_SESSION_OPEN) {
             pr_notice("mds%d is already opened\n", session->s_mds);
         } else {
             session->s_state = CEPH_MDS_SESSION_OPEN;
             session->s_features = features;
             renewed_caps(mdsc, session, 0);
             if (test_bit(CEPHFS_FEATURE_METRIC_COLLECT,
                      &session->s_features))
                 metric_schedule_delayed(&mdsc->metric);
         }
 
         /*
          * The connection maybe broken and the session in client
          * side has been reinitialized, need to update the seq
          * anyway.
          */
         if (!session->s_seq && seq)
             session->s_seq = seq;
 
         wake = 1;
         if (mdsc->stopping)
             __close_session(mdsc, session);
         break;
 
     case CEPH_SESSION_RENEWCAPS:
         if (session->s_renew_seq == seq)
             renewed_caps(mdsc, session, 1);
         break;
 
     case CEPH_SESSION_CLOSE:
         if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
             pr_info("mds%d reconnect denied\n", session->s_mds);
         session->s_state = CEPH_MDS_SESSION_CLOSED;
         cleanup_session_requests(mdsc, session);
         remove_session_caps(session);
         wake = 2; /* for good measure */
         wake_up_all(&mdsc->session_close_wq);
         break;
 
     case CEPH_SESSION_STALE:
         pr_info("mds%d caps went stale, renewing\n",
             session->s_mds);
         atomic_inc(&session->s_cap_gen);
         session->s_cap_ttl = jiffies - 1;
         send_renew_caps(mdsc, session);
         break;
 
     case CEPH_SESSION_RECALL_STATE:
         ceph_trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
         break;
 
     case CEPH_SESSION_FLUSHMSG:
         send_flushmsg_ack(mdsc, session, seq);
         break;
 
     case CEPH_SESSION_FORCE_RO:
         dout("force_session_readonly %p\n", session);
         spin_lock(&session->s_cap_lock);
         session->s_readonly = true;
         spin_unlock(&session->s_cap_lock);
         wake_up_session_caps(session, FORCE_RO);
         break;
 
     case CEPH_SESSION_REJECT:
         WARN_ON(session->s_state != CEPH_MDS_SESSION_OPENING);
         pr_info("mds%d rejected session\n", session->s_mds);
         session->s_state = CEPH_MDS_SESSION_REJECTED;
         cleanup_session_requests(mdsc, session);
         remove_session_caps(session);
         if (blocklisted)
             mdsc->fsc->blocklisted = true;
         wake = 2; /* for good measure */
         break;
 
     default:
         pr_err("mdsc_handle_session bad op %d mds%d\n", op, mds);
         WARN_ON(1);
     }
 
     mutex_unlock(&session->s_mutex);
     if (wake) {
         mutex_lock(&mdsc->mutex);
         __wake_requests(mdsc, &session->s_waiting);
         if (wake == 2)
             kick_requests(mdsc, mds);
         mutex_unlock(&mdsc->mutex);
     }
     if (op == CEPH_SESSION_CLOSE)
         ceph_put_mds_session(session);
     return;
 
 bad:
     pr_err("mdsc_handle_session corrupt message mds%d len %d\n", mds,
            (int)msg->front.iov_len);
     ceph_msg_dump(msg);
     return;
 }
 
 void ceph_mdsc_release_dir_caps(struct ceph_mds_request *req)
 {
     int dcaps;
 
     dcaps = xchg(&req->r_dir_caps, 0);
     if (dcaps) {
         dout("releasing r_dir_caps=%s\n", ceph_cap_string(dcaps));
         ceph_put_cap_refs(ceph_inode(req->r_parent), dcaps);
     }
 }
 
 void ceph_mdsc_release_dir_caps_no_check(struct ceph_mds_request *req)
 {
     int dcaps;
 
     dcaps = xchg(&req->r_dir_caps, 0);
     if (dcaps) {
         dout("releasing r_dir_caps=%s\n", ceph_cap_string(dcaps));
         ceph_put_cap_refs_no_check_caps(ceph_inode(req->r_parent),
                         dcaps);
     }
 }
 
 /*
  * called under session->mutex.
  */
 static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
                    struct ceph_mds_session *session)
 {
     struct ceph_mds_request *req, *nreq;
     struct rb_node *p;
 
     dout("replay_unsafe_requests mds%d\n", session->s_mds);
 
     mutex_lock(&mdsc->mutex);
     list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item)
         __send_request(session, req, true);
 
     /*
      * also re-send old requests when MDS enters reconnect stage. So that MDS
      * can process completed request in clientreplay stage.
      */
     p = rb_first(&mdsc->request_tree);
     while (p) {
         req = rb_entry(p, struct ceph_mds_request, r_node);
         p = rb_next(p);
         if (test_bit(CEPH_MDS_R_GOT_UNSAFE, &req->r_req_flags))
             continue;
         if (req->r_attempts == 0)
             continue; /* only old requests */
         if (!req->r_session)
             continue;
         if (req->r_session->s_mds != session->s_mds)
             continue;
 
         ceph_mdsc_release_dir_caps_no_check(req);
 
         __send_request(session, req, true);
     }
     mutex_unlock(&mdsc->mutex);
 }
 
 static int send_reconnect_partial(struct ceph_reconnect_state *recon_state)
 {
     struct ceph_msg *reply;
     struct ceph_pagelist *_pagelist;
     struct page *page;
     __le32 *addr;
     int err = -ENOMEM;
 
     if (!recon_state->allow_multi)
         return -ENOSPC;
 
     /* can't handle message that contains both caps and realm */
     BUG_ON(!recon_state->nr_caps == !recon_state->nr_realms);
 
     /* pre-allocate new pagelist */
     _pagelist = ceph_pagelist_alloc(GFP_NOFS);
     if (!_pagelist)
         return -ENOMEM;
 
     reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false);
     if (!reply)
         goto fail_msg;
 
     /* placeholder for nr_caps */
     err = ceph_pagelist_encode_32(_pagelist, 0);
     if (err < 0)
         goto fail;
 
     if (recon_state->nr_caps) {
         /* currently encoding caps */
         err = ceph_pagelist_encode_32(recon_state->pagelist, 0);
         if (err)
             goto fail;
     } else {
         /* placeholder for nr_realms (currently encoding relams) */
         err = ceph_pagelist_encode_32(_pagelist, 0);
         if (err < 0)
             goto fail;
     }
 
     err = ceph_pagelist_encode_8(recon_state->pagelist, 1);
     if (err)
         goto fail;
 
     page = list_first_entry(&recon_state->pagelist->head, struct page, lru);
     addr = kmap_atomic(page);
     if (recon_state->nr_caps) {
         /* currently encoding caps */
         *addr = cpu_to_le32(recon_state->nr_caps);
     } else {
         /* currently encoding relams */
         *(addr + 1) = cpu_to_le32(recon_state->nr_realms);
     }
     kunmap_atomic(addr);
 
     reply->hdr.version = cpu_to_le16(5);
     reply->hdr.compat_version = cpu_to_le16(4);
 
     reply->hdr.data_len = cpu_to_le32(recon_state->pagelist->length);
     ceph_msg_data_add_pagelist(reply, recon_state->pagelist);
 
     ceph_con_send(&recon_state->session->s_con, reply);
     ceph_pagelist_release(recon_state->pagelist);
 
     recon_state->pagelist = _pagelist;
     recon_state->nr_caps = 0;
     recon_state->nr_realms = 0;
     recon_state->msg_version = 5;
     return 0;
 fail:
     ceph_msg_put(reply);
 fail_msg:
     ceph_pagelist_release(_pagelist);
     return err;
 }
 
 static struct dentry* d_find_primary(struct inode *inode)
 {
     struct dentry *alias, *dn = NULL;
 
     if (hlist_empty(&inode->i_dentry))
         return NULL;
 
     spin_lock(&inode->i_lock);
     if (hlist_empty(&inode->i_dentry))
         goto out_unlock;
 
     if (S_ISDIR(inode->i_mode)) {
         alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
         if (!IS_ROOT(alias))
             dn = dget(alias);
         goto out_unlock;
     }
 
     hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
         spin_lock(&alias->d_lock);
         if (!d_unhashed(alias) &&
             (ceph_dentry(alias)->flags & CEPH_DENTRY_PRIMARY_LINK)) {
             dn = dget_dlock(alias);
         }
         spin_unlock(&alias->d_lock);
         if (dn)
             break;
     }
 out_unlock:
     spin_unlock(&inode->i_lock);
     return dn;
 }
 
 /*
  * Encode information about a cap for a reconnect with the MDS.
  */
 static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap,
               void *arg)
 {
     union {
         struct ceph_mds_cap_reconnect v2;
         struct ceph_mds_cap_reconnect_v1 v1;
     } rec;
     struct ceph_inode_info *ci = cap->ci;
     struct ceph_reconnect_state *recon_state = arg;
     struct ceph_pagelist *pagelist = recon_state->pagelist;
     struct dentry *dentry;
     char *path;
     int pathlen = 0, err;
     u64 pathbase;
     u64 snap_follows;
 
     dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
          inode, ceph_vinop(inode), cap, cap->cap_id,
          ceph_cap_string(cap->issued));
 
     dentry = d_find_primary(inode);
     if (dentry) {
         /* set pathbase to parent dir when msg_version >= 2 */
         path = ceph_mdsc_build_path(dentry, &pathlen, &pathbase,
                         recon_state->msg_version >= 2);
         dput(dentry);
         if (IS_ERR(path)) {
             err = PTR_ERR(path);
             goto out_err;
         }
     } else {
         path = NULL;
         pathbase = 0;
     }
 
     spin_lock(&ci->i_ceph_lock);
     cap->seq = 0;        /* reset cap seq */
     cap->issue_seq = 0;  /* and issue_seq */
     cap->mseq = 0;       /* and migrate_seq */
     cap->cap_gen = atomic_read(&cap->session->s_cap_gen);
 
     /* These are lost when the session goes away */
     if (S_ISDIR(inode->i_mode)) {
         if (cap->issued & CEPH_CAP_DIR_CREATE) {
             ceph_put_string(rcu_dereference_raw(ci->i_cached_layout.pool_ns));
             memset(&ci->i_cached_layout, 0, sizeof(ci->i_cached_layout));
         }
         cap->issued &= ~CEPH_CAP_ANY_DIR_OPS;
     }
 
     if (recon_state->msg_version >= 2) {
         rec.v2.cap_id = cpu_to_le64(cap->cap_id);
         rec.v2.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
         rec.v2.issued = cpu_to_le32(cap->issued);
         rec.v2.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
         rec.v2.pathbase = cpu_to_le64(pathbase);
         rec.v2.flock_len = (__force __le32)
             ((ci->i_ceph_flags & CEPH_I_ERROR_FILELOCK) ? 0 : 1);
     } else {
         rec.v1.cap_id = cpu_to_le64(cap->cap_id);
         rec.v1.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
         rec.v1.issued = cpu_to_le32(cap->issued);
         rec.v1.size = cpu_to_le64(i_size_read(inode));
         ceph_encode_timespec64(&rec.v1.mtime, &inode->i_mtime);
         ceph_encode_timespec64(&rec.v1.atime, &inode->i_atime);
         rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
         rec.v1.pathbase = cpu_to_le64(pathbase);
     }
 
     if (list_empty(&ci->i_cap_snaps)) {
         snap_follows = ci->i_head_snapc ? ci->i_head_snapc->seq : 0;
     } else {
         struct ceph_cap_snap *capsnap =
             list_first_entry(&ci->i_cap_snaps,
                      struct ceph_cap_snap, ci_item);
         snap_follows = capsnap->follows;
     }
     spin_unlock(&ci->i_ceph_lock);
 
     if (recon_state->msg_version >= 2) {
         int num_fcntl_locks, num_flock_locks;
         struct ceph_filelock *flocks = NULL;
         size_t struct_len, total_len = sizeof(u64);
         u8 struct_v = 0;
 
 encode_again:
         if (rec.v2.flock_len) {
             ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
         } else {
             num_fcntl_locks = 0;
             num_flock_locks = 0;
         }
         if (num_fcntl_locks + num_flock_locks > 0) {
             flocks = kmalloc_array(num_fcntl_locks + num_flock_locks,
                            sizeof(struct ceph_filelock),
                            GFP_NOFS);
             if (!flocks) {
                 err = -ENOMEM;
                 goto out_err;
             }
             err = ceph_encode_locks_to_buffer(inode, flocks,
                               num_fcntl_locks,
                               num_flock_locks);
             if (err) {
                 kfree(flocks);
                 flocks = NULL;
                 if (err == -ENOSPC)
                     goto encode_again;
                 goto out_err;
             }
         } else {
             kfree(flocks);
             flocks = NULL;
         }
 
         if (recon_state->msg_version >= 3) {
             /* version, compat_version and struct_len */
             total_len += 2 * sizeof(u8) + sizeof(u32);
             struct_v = 2;
         }
         /*
          * number of encoded locks is stable, so copy to pagelist
          */
         struct_len = 2 * sizeof(u32) +
                 (num_fcntl_locks + num_flock_locks) *
                 sizeof(struct ceph_filelock);
         rec.v2.flock_len = cpu_to_le32(struct_len);
 
         struct_len += sizeof(u32) + pathlen + sizeof(rec.v2);
 
         if (struct_v >= 2)
             struct_len += sizeof(u64); /* snap_follows */
 
         total_len += struct_len;
 
         if (pagelist->length + total_len > RECONNECT_MAX_SIZE) {
             err = send_reconnect_partial(recon_state);
             if (err)
                 goto out_freeflocks;
             pagelist = recon_state->pagelist;
         }
 
         err = ceph_pagelist_reserve(pagelist, total_len);
         if (err)
             goto out_freeflocks;
 
         ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
         if (recon_state->msg_version >= 3) {
             ceph_pagelist_encode_8(pagelist, struct_v);
             ceph_pagelist_encode_8(pagelist, 1);
             ceph_pagelist_encode_32(pagelist, struct_len);
         }
         ceph_pagelist_encode_string(pagelist, path, pathlen);
         ceph_pagelist_append(pagelist, &rec, sizeof(rec.v2));
         ceph_locks_to_pagelist(flocks, pagelist,
                        num_fcntl_locks, num_flock_locks);
         if (struct_v >= 2)
             ceph_pagelist_encode_64(pagelist, snap_follows);
 out_freeflocks:
         kfree(flocks);
     } else {
         err = ceph_pagelist_reserve(pagelist,
                         sizeof(u64) + sizeof(u32) +
                         pathlen + sizeof(rec.v1));
         if (err)
             goto out_err;
 
         ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
         ceph_pagelist_encode_string(pagelist, path, pathlen);
         ceph_pagelist_append(pagelist, &rec, sizeof(rec.v1));
     }
 
 out_err:
     ceph_mdsc_free_path(path, pathlen);
     if (!err)
         recon_state->nr_caps++;
     return err;
 }
 
 static int encode_snap_realms(struct ceph_mds_client *mdsc,
                   struct ceph_reconnect_state *recon_state)
 {
     struct rb_node *p;
     struct ceph_pagelist *pagelist = recon_state->pagelist;
     int err = 0;
 
     if (recon_state->msg_version >= 4) {
         err = ceph_pagelist_encode_32(pagelist, mdsc->num_snap_realms);
         if (err < 0)
             goto fail;
     }
 
     /*
      * snaprealms.  we provide mds with the ino, seq (version), and
      * parent for all of our realms.  If the mds has any newer info,
      * it will tell us.
      */
     for (p = rb_first(&mdsc->snap_realms); p; p = rb_next(p)) {
         struct ceph_snap_realm *realm =
                rb_entry(p, struct ceph_snap_realm, node);
         struct ceph_mds_snaprealm_reconnect sr_rec;
 
         if (recon_state->msg_version >= 4) {
             size_t need = sizeof(u8) * 2 + sizeof(u32) +
                       sizeof(sr_rec);
 
             if (pagelist->length + need > RECONNECT_MAX_SIZE) {
                 err = send_reconnect_partial(recon_state);
                 if (err)
                     goto fail;
                 pagelist = recon_state->pagelist;
             }
 
             err = ceph_pagelist_reserve(pagelist, need);
             if (err)
                 goto fail;
 
             ceph_pagelist_encode_8(pagelist, 1);
             ceph_pagelist_encode_8(pagelist, 1);
             ceph_pagelist_encode_32(pagelist, sizeof(sr_rec));
         }
 
         dout(" adding snap realm %llx seq %lld parent %llx\n",
              realm->ino, realm->seq, realm->parent_ino);
         sr_rec.ino = cpu_to_le64(realm->ino);
         sr_rec.seq = cpu_to_le64(realm->seq);
         sr_rec.parent = cpu_to_le64(realm->parent_ino);
 
         err = ceph_pagelist_append(pagelist, &sr_rec, sizeof(sr_rec));
         if (err)
             goto fail;
 
         recon_state->nr_realms++;
     }
 fail:
     return err;
 }
 
 
 /*
  * If an MDS fails and recovers, clients need to reconnect in order to
  * reestablish shared state.  This includes all caps issued through
  * this session _and_ the snap_realm hierarchy.  Because it's not
  * clear which snap realms the mds cares about, we send everything we
  * know about.. that ensures we'll then get any new info the
  * recovering MDS might have.
  *
  * This is a relatively heavyweight operation, but it's rare.
  */
 static void send_mds_reconnect(struct ceph_mds_client *mdsc,
                    struct ceph_mds_session *session)
 {
     struct ceph_msg *reply;
     int mds = session->s_mds;
     int err = -ENOMEM;
     struct ceph_reconnect_state recon_state = {
         .session = session,
     };
     LIST_HEAD(dispose);
 
     pr_info("mds%d reconnect start\n", mds);
 
     recon_state.pagelist = ceph_pagelist_alloc(GFP_NOFS);
     if (!recon_state.pagelist)
         goto fail_nopagelist;
 
     reply = ceph_msg_new2(CEPH_MSG_CLIENT_RECONNECT, 0, 1, GFP_NOFS, false);
     if (!reply)
         goto fail_nomsg;
 
     xa_destroy(&session->s_delegated_inos);
 
     mutex_lock(&session->s_mutex);
     session->s_state = CEPH_MDS_SESSION_RECONNECTING;
     session->s_seq = 0;
 
     dout("session %p state %s\n", session,
          ceph_session_state_name(session->s_state));
 
     atomic_inc(&session->s_cap_gen);
 
     spin_lock(&session->s_cap_lock);
     /* don't know if session is readonly */
     session->s_readonly = 0;
     /*
      * notify __ceph_remove_cap() that we are composing cap reconnect.
      * If a cap get released before being added to the cap reconnect,
      * __ceph_remove_cap() should skip queuing cap release.
      */
     session->s_cap_reconnect = 1;
     /* drop old cap expires; we're about to reestablish that state */
     detach_cap_releases(session, &dispose);
     spin_unlock(&session->s_cap_lock);
     dispose_cap_releases(mdsc, &dispose);
 
     /* trim unused caps to reduce MDS's cache rejoin time */
     if (mdsc->fsc->sb->s_root)
         shrink_dcache_parent(mdsc->fsc->sb->s_root);
 
     ceph_con_close(&session->s_con);
     ceph_con_open(&session->s_con,
               CEPH_ENTITY_TYPE_MDS, mds,
               ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
 
     /* replay unsafe requests */
     replay_unsafe_requests(mdsc, session);
 
     ceph_early_kick_flushing_caps(mdsc, session);
 
     down_read(&mdsc->snap_rwsem);
 
     /* placeholder for nr_caps */
     err = ceph_pagelist_encode_32(recon_state.pagelist, 0);
     if (err)
         goto fail;
 
     if (test_bit(CEPHFS_FEATURE_MULTI_RECONNECT, &session->s_features)) {
         recon_state.msg_version = 3;
         recon_state.allow_multi = true;
     } else if (session->s_con.peer_features & CEPH_FEATURE_MDSENC) {
         recon_state.msg_version = 3;
     } else {
         recon_state.msg_version = 2;
     }
     /* trsaverse this session's caps */
     err = ceph_iterate_session_caps(session, reconnect_caps_cb, &recon_state);
 
     spin_lock(&session->s_cap_lock);
     session->s_cap_reconnect = 0;
     spin_unlock(&session->s_cap_lock);
 
     if (err < 0)
         goto fail;
 
     /* check if all realms can be encoded into current message */
     if (mdsc->num_snap_realms) {
         size_t total_len =
             recon_state.pagelist->length +
             mdsc->num_snap_realms *
             sizeof(struct ceph_mds_snaprealm_reconnect);
         if (recon_state.msg_version >= 4) {
             /* number of realms */
             total_len += sizeof(u32);
             /* version, compat_version and struct_len */
             total_len += mdsc->num_snap_realms *
                      (2 * sizeof(u8) + sizeof(u32));
         }
         if (total_len > RECONNECT_MAX_SIZE) {
             if (!recon_state.allow_multi) {
                 err = -ENOSPC;
                 goto fail;
             }
             if (recon_state.nr_caps) {
                 err = send_reconnect_partial(&recon_state);
                 if (err)
                     goto fail;
             }
             recon_state.msg_version = 5;
         }
     }
 
     err = encode_snap_realms(mdsc, &recon_state);
     if (err < 0)
         goto fail;
 
     if (recon_state.msg_version >= 5) {
         err = ceph_pagelist_encode_8(recon_state.pagelist, 0);
         if (err < 0)
             goto fail;
     }
 
     if (recon_state.nr_caps || recon_state.nr_realms) {
         struct page *page =
             list_first_entry(&recon_state.pagelist->head,
                     struct page, lru);
         __le32 *addr = kmap_atomic(page);
         if (recon_state.nr_caps) {
             WARN_ON(recon_state.nr_realms != mdsc->num_snap_realms);
             *addr = cpu_to_le32(recon_state.nr_caps);
         } else if (recon_state.msg_version >= 4) {
             *(addr + 1) = cpu_to_le32(recon_state.nr_realms);
         }
         kunmap_atomic(addr);
     }
 
     reply->hdr.version = cpu_to_le16(recon_state.msg_version);
     if (recon_state.msg_version >= 4)
         reply->hdr.compat_version = cpu_to_le16(4);
 
     reply->hdr.data_len = cpu_to_le32(recon_state.pagelist->length);
     ceph_msg_data_add_pagelist(reply, recon_state.pagelist);
 
     ceph_con_send(&session->s_con, reply);
 
     mutex_unlock(&session->s_mutex);
 
     mutex_lock(&mdsc->mutex);
     __wake_requests(mdsc, &session->s_waiting);
     mutex_unlock(&mdsc->mutex);
 
     up_read(&mdsc->snap_rwsem);
     ceph_pagelist_release(recon_state.pagelist);
     return;
 
 fail:
     ceph_msg_put(reply);
     up_read(&mdsc->snap_rwsem);
     mutex_unlock(&session->s_mutex);
 fail_nomsg:
     ceph_pagelist_release(recon_state.pagelist);
 fail_nopagelist:
     pr_err("error %d preparing reconnect for mds%d\n", err, mds);
     return;
 }
 
 
 /*
  * compare old and new mdsmaps, kicking requests
  * and closing out old connections as necessary
  *
  * called under mdsc->mutex.
  */
 static void check_new_map(struct ceph_mds_client *mdsc,
               struct ceph_mdsmap *newmap,
               struct ceph_mdsmap *oldmap)
 {
     int i, j, err;
     int oldstate, newstate;
     struct ceph_mds_session *s;
     unsigned long targets[DIV_ROUND_UP(CEPH_MAX_MDS, sizeof(unsigned long))] = {0};
 
     dout("check_new_map new %u old %u\n",
          newmap->m_epoch, oldmap->m_epoch);
 
     if (newmap->m_info) {
         for (i = 0; i < newmap->possible_max_rank; i++) {
             for (j = 0; j < newmap->m_info[i].num_export_targets; j++)
                 set_bit(newmap->m_info[i].export_targets[j], targets);
         }
     }
 
     for (i = 0; i < oldmap->possible_max_rank && i < mdsc->max_sessions; i++) {
         if (!mdsc->sessions[i])
             continue;
         s = mdsc->sessions[i];
         oldstate = ceph_mdsmap_get_state(oldmap, i);
         newstate = ceph_mdsmap_get_state(newmap, i);
 
         dout("check_new_map mds%d state %s%s -> %s%s (session %s)\n",
              i, ceph_mds_state_name(oldstate),
              ceph_mdsmap_is_laggy(oldmap, i) ? " (laggy)" : "",
              ceph_mds_state_name(newstate),
              ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
              ceph_session_state_name(s->s_state));
 
         if (i >= newmap->possible_max_rank) {
             /* force close session for stopped mds */
             ceph_get_mds_session(s);
             __unregister_session(mdsc, s);
             __wake_requests(mdsc, &s->s_waiting);
             mutex_unlock(&mdsc->mutex);
 
             mutex_lock(&s->s_mutex);
             cleanup_session_requests(mdsc, s);
             remove_session_caps(s);
             mutex_unlock(&s->s_mutex);
 
             ceph_put_mds_session(s);
 
             mutex_lock(&mdsc->mutex);
             kick_requests(mdsc, i);
             continue;
         }
 
         if (memcmp(ceph_mdsmap_get_addr(oldmap, i),
                ceph_mdsmap_get_addr(newmap, i),
                sizeof(struct ceph_entity_addr))) {
             /* just close it */
             mutex_unlock(&mdsc->mutex);
             mutex_lock(&s->s_mutex);
             mutex_lock(&mdsc->mutex);
             ceph_con_close(&s->s_con);
             mutex_unlock(&s->s_mutex);
             s->s_state = CEPH_MDS_SESSION_RESTARTING;
         } else if (oldstate == newstate) {
             continue;  /* nothing new with this mds */
         }
 
         /*
          * send reconnect?
          */
         if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
             newstate >= CEPH_MDS_STATE_RECONNECT) {
             mutex_unlock(&mdsc->mutex);
             clear_bit(i, targets);
             send_mds_reconnect(mdsc, s);
             mutex_lock(&mdsc->mutex);
         }
 
         /*
          * kick request on any mds that has gone active.
          */
         if (oldstate < CEPH_MDS_STATE_ACTIVE &&
             newstate >= CEPH_MDS_STATE_ACTIVE) {
             if (oldstate != CEPH_MDS_STATE_CREATING &&
                 oldstate != CEPH_MDS_STATE_STARTING)
                 pr_info("mds%d recovery completed\n", s->s_mds);
             kick_requests(mdsc, i);
             mutex_unlock(&mdsc->mutex);
             mutex_lock(&s->s_mutex);
             mutex_lock(&mdsc->mutex);
             ceph_kick_flushing_caps(mdsc, s);
             mutex_unlock(&s->s_mutex);
             wake_up_session_caps(s, RECONNECT);
         }
     }
 
     /*
      * Only open and reconnect sessions that don't exist yet.
      */
     for (i = 0; i < newmap->possible_max_rank; i++) {
         /*
          * In case the import MDS is crashed just after
          * the EImportStart journal is flushed, so when
          * a standby MDS takes over it and is replaying
          * the EImportStart journal the new MDS daemon
          * will wait the client to reconnect it, but the
          * client may never register/open the session yet.
          *
          * Will try to reconnect that MDS daemon if the
          * rank number is in the export targets array and
          * is the up:reconnect state.
          */
         newstate = ceph_mdsmap_get_state(newmap, i);
         if (!test_bit(i, targets) || newstate != CEPH_MDS_STATE_RECONNECT)
             continue;
 
         /*
          * The session maybe registered and opened by some
          * requests which were choosing random MDSes during
          * the mdsc->mutex's unlock/lock gap below in rare
          * case. But the related MDS daemon will just queue
          * that requests and be still waiting for the client's
          * reconnection request in up:reconnect state.
          */
         s = __ceph_lookup_mds_session(mdsc, i);
         if (likely(!s)) {
             s = __open_export_target_session(mdsc, i);
             if (IS_ERR(s)) {
                 err = PTR_ERR(s);
                 pr_err("failed to open export target session, err %d\n",
                        err);
                 continue;
             }
         }
         dout("send reconnect to export target mds.%d\n", i);
         mutex_unlock(&mdsc->mutex);
         send_mds_reconnect(mdsc, s);
         ceph_put_mds_session(s);
         mutex_lock(&mdsc->mutex);
     }
 
     for (i = 0; i < newmap->possible_max_rank && i < mdsc->max_sessions; i++) {
         s = mdsc->sessions[i];
         if (!s)
             continue;
         if (!ceph_mdsmap_is_laggy(newmap, i))
             continue;
         if (s->s_state == CEPH_MDS_SESSION_OPEN ||
             s->s_state == CEPH_MDS_SESSION_HUNG ||
             s->s_state == CEPH_MDS_SESSION_CLOSING) {
             dout(" connecting to export targets of laggy mds%d\n",
                  i);
             __open_export_target_sessions(mdsc, s);
         }
     }
 }
 
 
 
 /*
  * leases
  */
 
 /*
  * caller must hold session s_mutex, dentry->d_lock
  */
 void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry)
 {
     struct ceph_dentry_info *di = ceph_dentry(dentry);
 
     ceph_put_mds_session(di->lease_session);
     di->lease_session = NULL;
 }
 
 static void handle_lease(struct ceph_mds_client *mdsc,
              struct ceph_mds_session *session,
              struct ceph_msg *msg)
 {
     struct super_block *sb = mdsc->fsc->sb;
     struct inode *inode;
     struct dentry *parent, *dentry;
     struct ceph_dentry_info *di;
     int mds = session->s_mds;
     struct ceph_mds_lease *h = msg->front.iov_base;
     u32 seq;
     struct ceph_vino vino;
     struct qstr dname;
     int release = 0;
 
     dout("handle_lease from mds%d\n", mds);
 
     /* decode */
     if (msg->front.iov_len < sizeof(*h) + sizeof(u32))
         goto bad;
     vino.ino = le64_to_cpu(h->ino);
     vino.snap = CEPH_NOSNAP;
     seq = le32_to_cpu(h->seq);
     dname.len = get_unaligned_le32(h + 1);
     if (msg->front.iov_len < sizeof(*h) + sizeof(u32) + dname.len)
         goto bad;
     dname.name = (void *)(h + 1) + sizeof(u32);
 
     /* lookup inode */
     inode = ceph_find_inode(sb, vino);
     dout("handle_lease %s, ino %llx %p %.*s\n",
          ceph_lease_op_name(h->action), vino.ino, inode,
          dname.len, dname.name);
 
     mutex_lock(&session->s_mutex);
     inc_session_sequence(session);
 
     if (!inode) {
         dout("handle_lease no inode %llx\n", vino.ino);
         goto release;
     }
 
     /* dentry */
     parent = d_find_alias(inode);
     if (!parent) {
         dout("no parent dentry on inode %p\n", inode);
         WARN_ON(1);
         goto release;  /* hrm... */
     }
     dname.hash = full_name_hash(parent, dname.name, dname.len);
     dentry = d_lookup(parent, &dname);
     dput(parent);
     if (!dentry)
         goto release;
 
     spin_lock(&dentry->d_lock);
     di = ceph_dentry(dentry);
     switch (h->action) {
     case CEPH_MDS_LEASE_REVOKE:
         if (di->lease_session == session) {
             if (ceph_seq_cmp(di->lease_seq, seq) > 0)
                 h->seq = cpu_to_le32(di->lease_seq);
             __ceph_mdsc_drop_dentry_lease(dentry);
         }
         release = 1;
         break;
 
     case CEPH_MDS_LEASE_RENEW:
         if (di->lease_session == session &&
             di->lease_gen == atomic_read(&session->s_cap_gen) &&
             di->lease_renew_from &&
             di->lease_renew_after == 0) {
             unsigned long duration =
                 msecs_to_jiffies(le32_to_cpu(h->duration_ms));
 
             di->lease_seq = seq;
             di->time = di->lease_renew_from + duration;
             di->lease_renew_after = di->lease_renew_from +
                 (duration >> 1);
             di->lease_renew_from = 0;
         }
         break;
     }
     spin_unlock(&dentry->d_lock);
     dput(dentry);
 
     if (!release)
         goto out;
 
 release:
     /* let's just reuse the same message */
     h->action = CEPH_MDS_LEASE_REVOKE_ACK;
     ceph_msg_get(msg);
     ceph_con_send(&session->s_con, msg);
 
 out:
     mutex_unlock(&session->s_mutex);
     iput(inode);
     return;
 
 bad:
     pr_err("corrupt lease message\n");
     ceph_msg_dump(msg);
 }
 
 void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
                   struct dentry *dentry, char action,
                   u32 seq)
 {
     struct ceph_msg *msg;
     struct ceph_mds_lease *lease;
     struct inode *dir;
     int len = sizeof(*lease) + sizeof(u32) + NAME_MAX;
 
     dout("lease_send_msg identry %p %s to mds%d\n",
          dentry, ceph_lease_op_name(action), session->s_mds);
 
     msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, GFP_NOFS, false);
     if (!msg)
         return;
     lease = msg->front.iov_base;
     lease->action = action;
     lease->seq = cpu_to_le32(seq);
 
     spin_lock(&dentry->d_lock);
     dir = d_inode(dentry->d_parent);
     lease->ino = cpu_to_le64(ceph_ino(dir));
     lease->first = lease->last = cpu_to_le64(ceph_snap(dir));
 
     put_unaligned_le32(dentry->d_name.len, lease + 1);
     memcpy((void *)(lease + 1) + 4,
            dentry->d_name.name, dentry->d_name.len);
     spin_unlock(&dentry->d_lock);
 
     ceph_con_send(&session->s_con, msg);
 }
 
 /*
  * lock unlock the session, to wait ongoing session activities
  */
 static void lock_unlock_session(struct ceph_mds_session *s)
 {
     mutex_lock(&s->s_mutex);
     mutex_unlock(&s->s_mutex);
 }
 
 static void maybe_recover_session(struct ceph_mds_client *mdsc)
 {
     struct ceph_fs_client *fsc = mdsc->fsc;
 
     if (!ceph_test_mount_opt(fsc, CLEANRECOVER))
         return;
 
     if (READ_ONCE(fsc->mount_state) != CEPH_MOUNT_MOUNTED)
         return;
 
     if (!READ_ONCE(fsc->blocklisted))
         return;
 
     pr_info("auto reconnect after blocklisted\n");
     ceph_force_reconnect(fsc->sb);
 }
 
 bool check_session_state(struct ceph_mds_session *s)
 {
     switch (s->s_state) {
     case CEPH_MDS_SESSION_OPEN:
         if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
             s->s_state = CEPH_MDS_SESSION_HUNG;
             pr_info("mds%d hung\n", s->s_mds);
         }
         break;
     case CEPH_MDS_SESSION_CLOSING:
     case CEPH_MDS_SESSION_NEW:
     case CEPH_MDS_SESSION_RESTARTING:
     case CEPH_MDS_SESSION_CLOSED:
     case CEPH_MDS_SESSION_REJECTED:
         return false;
     }
 
     return true;
 }
 
 /*
  * If the sequence is incremented while we're waiting on a REQUEST_CLOSE reply,
  * then we need to retransmit that request.
  */
 void inc_session_sequence(struct ceph_mds_session *s)
 {
     lockdep_assert_held(&s->s_mutex);
 
     s->s_seq++;
 
     if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
         int ret;
 
         dout("resending session close request for mds%d\n", s->s_mds);
         ret = request_close_session(s);
         if (ret < 0)
             pr_err("unable to close session to mds%d: %d\n",
                    s->s_mds, ret);
     }
 }
 
 /*
  * delayed work -- periodically trim expired leases, renew caps with mds.  If
  * the @delay parameter is set to 0 or if it's more than 5 secs, the default
  * workqueue delay value of 5 secs will be used.
  */
 static void schedule_delayed(struct ceph_mds_client *mdsc, unsigned long delay)
 {
     unsigned long max_delay = HZ * 5;
 
     /* 5 secs default delay */
     if (!delay || (delay > max_delay))
         delay = max_delay;
     schedule_delayed_work(&mdsc->delayed_work,
                   round_jiffies_relative(delay));
 }
 
 static void delayed_work(struct work_struct *work)
 {
     struct ceph_mds_client *mdsc =
         container_of(work, struct ceph_mds_client, delayed_work.work);
     unsigned long delay;
     int renew_interval;
     int renew_caps;
     int i;
 
     dout("mdsc delayed_work\n");
 
     if (mdsc->stopping)
         return;
 
     mutex_lock(&mdsc->mutex);
     renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
     renew_caps = time_after_eq(jiffies, HZ*renew_interval +
                    mdsc->last_renew_caps);
     if (renew_caps)
         mdsc->last_renew_caps = jiffies;
 
     for (i = 0; i < mdsc->max_sessions; i++) {
         struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
         if (!s)
             continue;
 
         if (!check_session_state(s)) {
             ceph_put_mds_session(s);
             continue;
         }
         mutex_unlock(&mdsc->mutex);
 
         mutex_lock(&s->s_mutex);
         if (renew_caps)
             send_renew_caps(mdsc, s);
         else
             ceph_con_keepalive(&s->s_con);
         if (s->s_state == CEPH_MDS_SESSION_OPEN ||
             s->s_state == CEPH_MDS_SESSION_HUNG)
             ceph_send_cap_releases(mdsc, s);
         mutex_unlock(&s->s_mutex);
         ceph_put_mds_session(s);
 
         mutex_lock(&mdsc->mutex);
     }
     mutex_unlock(&mdsc->mutex);
 
     delay = ceph_check_delayed_caps(mdsc);
 
     ceph_queue_cap_reclaim_work(mdsc);
 
     ceph_trim_snapid_map(mdsc);
 
     maybe_recover_session(mdsc);
 
     schedule_delayed(mdsc, delay);
 }
 
 int ceph_mdsc_init(struct ceph_fs_client *fsc)
 
 {
     struct ceph_mds_client *mdsc;
     int err;
 
     mdsc = kzalloc(sizeof(struct ceph_mds_client), GFP_NOFS);
     if (!mdsc)
         return -ENOMEM;
     mdsc->fsc = fsc;
     mutex_init(&mdsc->mutex);
     mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
     if (!mdsc->mdsmap) {
         err = -ENOMEM;
         goto err_mdsc;
     }
 
     init_completion(&mdsc->safe_umount_waiters);
     init_waitqueue_head(&mdsc->session_close_wq);
     INIT_LIST_HEAD(&mdsc->waiting_for_map);
     mdsc->quotarealms_inodes = RB_ROOT;
     mutex_init(&mdsc->quotarealms_inodes_mutex);
     init_rwsem(&mdsc->snap_rwsem);
     mdsc->snap_realms = RB_ROOT;
     INIT_LIST_HEAD(&mdsc->snap_empty);
     spin_lock_init(&mdsc->snap_empty_lock);
     mdsc->request_tree = RB_ROOT;
     INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
     mdsc->last_renew_caps = jiffies;
     INIT_LIST_HEAD(&mdsc->cap_delay_list);
     INIT_LIST_HEAD(&mdsc->cap_wait_list);
     spin_lock_init(&mdsc->cap_delay_lock);
     INIT_LIST_HEAD(&mdsc->snap_flush_list);
     spin_lock_init(&mdsc->snap_flush_lock);
     mdsc->last_cap_flush_tid = 1;
     INIT_LIST_HEAD(&mdsc->cap_flush_list);
     INIT_LIST_HEAD(&mdsc->cap_dirty_migrating);
     spin_lock_init(&mdsc->cap_dirty_lock);
     init_waitqueue_head(&mdsc->cap_flushing_wq);
     INIT_WORK(&mdsc->cap_reclaim_work, ceph_cap_reclaim_work);
     err = ceph_metric_init(&mdsc->metric);
     if (err)
         goto err_mdsmap;
 
     spin_lock_init(&mdsc->dentry_list_lock);
     INIT_LIST_HEAD(&mdsc->dentry_leases);
     INIT_LIST_HEAD(&mdsc->dentry_dir_leases);
 
     ceph_caps_init(mdsc);
     ceph_adjust_caps_max_min(mdsc, fsc->mount_options);
 
     spin_lock_init(&mdsc->snapid_map_lock);
     mdsc->snapid_map_tree = RB_ROOT;
     INIT_LIST_HEAD(&mdsc->snapid_map_lru);
 
     init_rwsem(&mdsc->pool_perm_rwsem);
     mdsc->pool_perm_tree = RB_ROOT;
 
     strscpy(mdsc->nodename, utsname()->nodename,
         sizeof(mdsc->nodename));
 
     fsc->mdsc = mdsc;
     return 0;
 
 err_mdsmap:
     kfree(mdsc->mdsmap);
 err_mdsc:
     kfree(mdsc);
     return err;
 }
 
 /*
  * Wait for safe replies on open mds requests.  If we time out, drop
  * all requests from the tree to avoid dangling dentry refs.
  */
 static void wait_requests(struct ceph_mds_client *mdsc)
 {
     struct ceph_options *opts = mdsc->fsc->client->options;
     struct ceph_mds_request *req;
 
     mutex_lock(&mdsc->mutex);
     if (__get_oldest_req(mdsc)) {
         mutex_unlock(&mdsc->mutex);
 
         dout("wait_requests waiting for requests\n");
         wait_for_completion_timeout(&mdsc->safe_umount_waiters,
                     ceph_timeout_jiffies(opts->mount_timeout));
 
         /* tear down remaining requests */
         mutex_lock(&mdsc->mutex);
         while ((req = __get_oldest_req(mdsc))) {
             dout("wait_requests timed out on tid %llu\n",
                  req->r_tid);
             list_del_init(&req->r_wait);
             __unregister_request(mdsc, req);
         }
     }
     mutex_unlock(&mdsc->mutex);
     dout("wait_requests done\n");
 }
 
 void send_flush_mdlog(struct ceph_mds_session *s)
 {
     struct ceph_msg *msg;
 
     /*
      * Pre-luminous MDS crashes when it sees an unknown session request
      */
     if (!CEPH_HAVE_FEATURE(s->s_con.peer_features, SERVER_LUMINOUS))
         return;
 
     mutex_lock(&s->s_mutex);
     dout("request mdlog flush to mds%d (%s)s seq %lld\n", s->s_mds,
          ceph_session_state_name(s->s_state), s->s_seq);
     msg = ceph_create_session_msg(CEPH_SESSION_REQUEST_FLUSH_MDLOG,
                       s->s_seq);
     if (!msg) {
         pr_err("failed to request mdlog flush to mds%d (%s) seq %lld\n",
                s->s_mds, ceph_session_state_name(s->s_state), s->s_seq);
     } else {
         ceph_con_send(&s->s_con, msg);
     }
     mutex_unlock(&s->s_mutex);
 }
 
 /*
  * called before mount is ro, and before dentries are torn down.
  * (hmm, does this still race with new lookups?)
  */
 void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
 {
     dout("pre_umount\n");
     mdsc->stopping = 1;
 
     ceph_mdsc_iterate_sessions(mdsc, send_flush_mdlog, true);
     ceph_mdsc_iterate_sessions(mdsc, lock_unlock_session, false);
     ceph_flush_dirty_caps(mdsc);
     wait_requests(mdsc);
 
     /*
      * wait for reply handlers to drop their request refs and
      * their inode/dcache refs
      */
     ceph_msgr_flush();
 
     ceph_cleanup_quotarealms_inodes(mdsc);
 }
 
 /*
  * flush the mdlog and wait for all write mds requests to flush.
  */
 static void flush_mdlog_and_wait_mdsc_unsafe_requests(struct ceph_mds_client *mdsc,
                          u64 want_tid)
 {
     struct ceph_mds_request *req = NULL, *nextreq;
     struct ceph_mds_session *last_session = NULL;
     struct rb_node *n;
 
     mutex_lock(&mdsc->mutex);
     dout("%s want %lld\n", __func__, want_tid);
 restart:
     req = __get_oldest_req(mdsc);
     while (req && req->r_tid <= want_tid) {
         /* find next request */
         n = rb_next(&req->r_node);
         if (n)
             nextreq = rb_entry(n, struct ceph_mds_request, r_node);
         else
             nextreq = NULL;
         if (req->r_op != CEPH_MDS_OP_SETFILELOCK &&
             (req->r_op & CEPH_MDS_OP_WRITE)) {
             struct ceph_mds_session *s = req->r_session;
 
             if (!s) {
                 req = nextreq;
                 continue;
             }
 
             /* write op */
             ceph_mdsc_get_request(req);
             if (nextreq)
                 ceph_mdsc_get_request(nextreq);
             s = ceph_get_mds_session(s);
             mutex_unlock(&mdsc->mutex);
 
             /* send flush mdlog request to MDS */
             if (last_session != s) {
                 send_flush_mdlog(s);
                 ceph_put_mds_session(last_session);
                 last_session = s;
             } else {
                 ceph_put_mds_session(s);
             }
             dout("%s wait on %llu (want %llu)\n", __func__,
                  req->r_tid, want_tid);
             wait_for_completion(&req->r_safe_completion);
 
             mutex_lock(&mdsc->mutex);
             ceph_mdsc_put_request(req);
             if (!nextreq)
                 break;  /* next dne before, so we're done! */
             if (RB_EMPTY_NODE(&nextreq->r_node)) {
                 /* next request was removed from tree */
                 ceph_mdsc_put_request(nextreq);
                 goto restart;
             }
             ceph_mdsc_put_request(nextreq);  /* won't go away */
         }
         req = nextreq;
     }
     mutex_unlock(&mdsc->mutex);
     ceph_put_mds_session(last_session);
     dout("%s done\n", __func__);
 }
 
 void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
 {
     u64 want_tid, want_flush;
 
     if (READ_ONCE(mdsc->fsc->mount_state) >= CEPH_MOUNT_SHUTDOWN)
         return;
 
     dout("sync\n");
     mutex_lock(&mdsc->mutex);
     want_tid = mdsc->last_tid;
     mutex_unlock(&mdsc->mutex);
 
     ceph_flush_dirty_caps(mdsc);
     spin_lock(&mdsc->cap_dirty_lock);
     want_flush = mdsc->last_cap_flush_tid;
     if (!list_empty(&mdsc->cap_flush_list)) {
         struct ceph_cap_flush *cf =
             list_last_entry(&mdsc->cap_flush_list,
                     struct ceph_cap_flush, g_list);
         cf->wake = true;
     }
     spin_unlock(&mdsc->cap_dirty_lock);
 
     dout("sync want tid %lld flush_seq %lld\n",
          want_tid, want_flush);
 
     flush_mdlog_and_wait_mdsc_unsafe_requests(mdsc, want_tid);
     wait_caps_flush(mdsc, want_flush);
 }
 
 /*
  * true if all sessions are closed, or we force unmount
  */
 static bool done_closing_sessions(struct ceph_mds_client *mdsc, int skipped)
 {
     if (READ_ONCE(mdsc->fsc->mount_state) == CEPH_MOUNT_SHUTDOWN)
         return true;
     return atomic_read(&mdsc->num_sessions) <= skipped;
 }
 
 /*
  * called after sb is ro.
  */
 void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
 {
     struct ceph_options *opts = mdsc->fsc->client->options;
     struct ceph_mds_session *session;
     int i;
     int skipped = 0;
 
     dout("close_sessions\n");
 
     /* close sessions */
     mutex_lock(&mdsc->mutex);
     for (i = 0; i < mdsc->max_sessions; i++) {
         session = __ceph_lookup_mds_session(mdsc, i);
         if (!session)
             continue;
         mutex_unlock(&mdsc->mutex);
         mutex_lock(&session->s_mutex);
         if (__close_session(mdsc, session) <= 0)
             skipped++;
         mutex_unlock(&session->s_mutex);
         ceph_put_mds_session(session);
         mutex_lock(&mdsc->mutex);
     }
     mutex_unlock(&mdsc->mutex);
 
     dout("waiting for sessions to close\n");
     wait_event_timeout(mdsc->session_close_wq,
                done_closing_sessions(mdsc, skipped),
                ceph_timeout_jiffies(opts->mount_timeout));
 
     /* tear down remaining sessions */
     mutex_lock(&mdsc->mutex);
     for (i = 0; i < mdsc->max_sessions; i++) {
         if (mdsc->sessions[i]) {
             session = ceph_get_mds_session(mdsc->sessions[i]);
             __unregister_session(mdsc, session);
             mutex_unlock(&mdsc->mutex);
             mutex_lock(&session->s_mutex);
             remove_session_caps(session);
             mutex_unlock(&session->s_mutex);
             ceph_put_mds_session(session);
             mutex_lock(&mdsc->mutex);
         }
     }
     WARN_ON(!list_empty(&mdsc->cap_delay_list));
     mutex_unlock(&mdsc->mutex);
 
     ceph_cleanup_snapid_map(mdsc);
     ceph_cleanup_global_and_empty_realms(mdsc);
 
     cancel_work_sync(&mdsc->cap_reclaim_work);
     cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
 
     dout("stopped\n");
 }
 
 void ceph_mdsc_force_umount(struct ceph_mds_client *mdsc)
 {
     struct ceph_mds_session *session;
     int mds;
 
     dout("force umount\n");
 
     mutex_lock(&mdsc->mutex);
     for (mds = 0; mds < mdsc->max_sessions; mds++) {
         session = __ceph_lookup_mds_session(mdsc, mds);
         if (!session)
             continue;
 
         if (session->s_state == CEPH_MDS_SESSION_REJECTED)
             __unregister_session(mdsc, session);
         __wake_requests(mdsc, &session->s_waiting);
         mutex_unlock(&mdsc->mutex);
 
         mutex_lock(&session->s_mutex);
         __close_session(mdsc, session);
         if (session->s_state == CEPH_MDS_SESSION_CLOSING) {
             cleanup_session_requests(mdsc, session);
             remove_session_caps(session);
         }
         mutex_unlock(&session->s_mutex);
         ceph_put_mds_session(session);
 
         mutex_lock(&mdsc->mutex);
         kick_requests(mdsc, mds);
     }
     __wake_requests(mdsc, &mdsc->waiting_for_map);
     mutex_unlock(&mdsc->mutex);
 }
 
 static void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
 {
     dout("stop\n");
     /*
      * Make sure the delayed work stopped before releasing
      * the resources.
      *
      * Because the cancel_delayed_work_sync() will only
      * guarantee that the work finishes executing. But the
      * delayed work will re-arm itself again after that.
      */
     flush_delayed_work(&mdsc->delayed_work);
 
     if (mdsc->mdsmap)
         ceph_mdsmap_destroy(mdsc->mdsmap);
     kfree(mdsc->sessions);
     ceph_caps_finalize(mdsc);
     ceph_pool_perm_destroy(mdsc);
 }
 
 void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
 {
     struct ceph_mds_client *mdsc = fsc->mdsc;
     dout("mdsc_destroy %p\n", mdsc);
 
     if (!mdsc)
         return;
 
     /* flush out any connection work with references to us */
     ceph_msgr_flush();
 
     ceph_mdsc_stop(mdsc);
 
     ceph_metric_destroy(&mdsc->metric);
 
     fsc->mdsc = NULL;
     kfree(mdsc);
     dout("mdsc_destroy %p done\n", mdsc);
 }
 
 void ceph_mdsc_handle_fsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
 {
     struct ceph_fs_client *fsc = mdsc->fsc;
     const char *mds_namespace = fsc->mount_options->mds_namespace;
     void *p = msg->front.iov_base;
     void *end = p + msg->front.iov_len;
     u32 epoch;
     u32 num_fs;
     u32 mount_fscid = (u32)-1;
     int err = -EINVAL;
 
     ceph_decode_need(&p, end, sizeof(u32), bad);
     epoch = ceph_decode_32(&p);
 
     dout("handle_fsmap epoch %u\n", epoch);
 
     /* struct_v, struct_cv, map_len, epoch, legacy_client_fscid */
     ceph_decode_skip_n(&p, end, 2 + sizeof(u32) * 3, bad);
 
     ceph_decode_32_safe(&p, end, num_fs, bad);
     while (num_fs-- > 0) {
         void *info_p, *info_end;
         u32 info_len;
         u32 fscid, namelen;
 
         ceph_decode_need(&p, end, 2 + sizeof(u32), bad);
         p += 2;     // info_v, info_cv
         info_len = ceph_decode_32(&p);
         ceph_decode_need(&p, end, info_len, bad);
         info_p = p;
         info_end = p + info_len;
         p = info_end;
 
         ceph_decode_need(&info_p, info_end, sizeof(u32) * 2, bad);
         fscid = ceph_decode_32(&info_p);
         namelen = ceph_decode_32(&info_p);
         ceph_decode_need(&info_p, info_end, namelen, bad);
 
         if (mds_namespace &&
             strlen(mds_namespace) == namelen &&
             !strncmp(mds_namespace, (char *)info_p, namelen)) {
             mount_fscid = fscid;
             break;
         }
     }
 
     ceph_monc_got_map(&fsc->client->monc, CEPH_SUB_FSMAP, epoch);
     if (mount_fscid != (u32)-1) {
         fsc->client->monc.fs_cluster_id = mount_fscid;
         ceph_monc_want_map(&fsc->client->monc, CEPH_SUB_MDSMAP,
                    0, true);
         ceph_monc_renew_subs(&fsc->client->monc);
     } else {
         err = -ENOENT;
         goto err_out;
     }
     return;
 
 bad:
     pr_err("error decoding fsmap %d. Shutting down mount.\n", err);
     ceph_umount_begin(mdsc->fsc->sb);
 err_out:
     mutex_lock(&mdsc->mutex);
     mdsc->mdsmap_err = err;
     __wake_requests(mdsc, &mdsc->waiting_for_map);
     mutex_unlock(&mdsc->mutex);
 }
 
 /*
  * handle mds map update.
  */
 void ceph_mdsc_handle_mdsmap(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
 {
     u32 epoch;
     u32 maplen;
     void *p = msg->front.iov_base;
     void *end = p + msg->front.iov_len;
     struct ceph_mdsmap *newmap, *oldmap;
     struct ceph_fsid fsid;
     int err = -EINVAL;
 
     ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
     ceph_decode_copy(&p, &fsid, sizeof(fsid));
     if (ceph_check_fsid(mdsc->fsc->client, &fsid) < 0)
         return;
     epoch = ceph_decode_32(&p);
     maplen = ceph_decode_32(&p);
     dout("handle_map epoch %u len %d\n", epoch, (int)maplen);
 
     /* do we need it? */
     mutex_lock(&mdsc->mutex);
     if (mdsc->mdsmap && epoch <= mdsc->mdsmap->m_epoch) {
         dout("handle_map epoch %u <= our %u\n",
              epoch, mdsc->mdsmap->m_epoch);
         mutex_unlock(&mdsc->mutex);
         return;
     }
 
     newmap = ceph_mdsmap_decode(&p, end, ceph_msgr2(mdsc->fsc->client));
     if (IS_ERR(newmap)) {
         err = PTR_ERR(newmap);
         goto bad_unlock;
     }
 
     /* swap into place */
     if (mdsc->mdsmap) {
         oldmap = mdsc->mdsmap;
         mdsc->mdsmap = newmap;
         check_new_map(mdsc, newmap, oldmap);
         ceph_mdsmap_destroy(oldmap);
     } else {
         mdsc->mdsmap = newmap;  /* first mds map */
     }
     mdsc->fsc->max_file_size = min((loff_t)mdsc->mdsmap->m_max_file_size,
                     MAX_LFS_FILESIZE);
 
     __wake_requests(mdsc, &mdsc->waiting_for_map);
     ceph_monc_got_map(&mdsc->fsc->client->monc, CEPH_SUB_MDSMAP,
               mdsc->mdsmap->m_epoch);
 
     mutex_unlock(&mdsc->mutex);
     schedule_delayed(mdsc, 0);
     return;
 
 bad_unlock:
     mutex_unlock(&mdsc->mutex);
 bad:
     pr_err("error decoding mdsmap %d. Shutting down mount.\n", err);
     ceph_umount_begin(mdsc->fsc->sb);
     return;
 }
 
 static struct ceph_connection *mds_get_con(struct ceph_connection *con)
 {
     struct ceph_mds_session *s = con->private;
 
     if (ceph_get_mds_session(s))
         return con;
     return NULL;
 }
 
 static void mds_put_con(struct ceph_connection *con)
 {
     struct ceph_mds_session *s = con->private;
 
     ceph_put_mds_session(s);
 }
 
 /*
  * if the client is unresponsive for long enough, the mds will kill
  * the session entirely.
  */
 static void mds_peer_reset(struct ceph_connection *con)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
 
     pr_warn("mds%d closed our session\n", s->s_mds);
     send_mds_reconnect(mdsc, s);
 }
 
 static void mds_dispatch(struct ceph_connection *con, struct ceph_msg *msg)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
     int type = le16_to_cpu(msg->hdr.type);
 
     mutex_lock(&mdsc->mutex);
     if (__verify_registered_session(mdsc, s) < 0) {
         mutex_unlock(&mdsc->mutex);
         goto out;
     }
     mutex_unlock(&mdsc->mutex);
 
     switch (type) {
     case CEPH_MSG_MDS_MAP:
         ceph_mdsc_handle_mdsmap(mdsc, msg);
         break;
     case CEPH_MSG_FS_MAP_USER:
         ceph_mdsc_handle_fsmap(mdsc, msg);
         break;
     case CEPH_MSG_CLIENT_SESSION:
         handle_session(s, msg);
         break;
     case CEPH_MSG_CLIENT_REPLY:
         handle_reply(s, msg);
         break;
     case CEPH_MSG_CLIENT_REQUEST_FORWARD:
         handle_forward(mdsc, s, msg);
         break;
     case CEPH_MSG_CLIENT_CAPS:
         ceph_handle_caps(s, msg);
         break;
     case CEPH_MSG_CLIENT_SNAP:
         ceph_handle_snap(mdsc, s, msg);
         break;
     case CEPH_MSG_CLIENT_LEASE:
         handle_lease(mdsc, s, msg);
         break;
     case CEPH_MSG_CLIENT_QUOTA:
         ceph_handle_quota(mdsc, s, msg);
         break;
 
     default:
         pr_err("received unknown message type %d %s\n", type,
                ceph_msg_type_name(type));
     }
 out:
     ceph_msg_put(msg);
 }
 
 /*
  * authentication
  */
 
 /*
  * Note: returned pointer is the address of a structure that's
  * managed separately.  Caller must *not* attempt to free it.
  */
 static struct ceph_auth_handshake *
 mds_get_authorizer(struct ceph_connection *con, int *proto, int force_new)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
     struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
     struct ceph_auth_handshake *auth = &s->s_auth;
     int ret;
 
     ret = __ceph_auth_get_authorizer(ac, auth, CEPH_ENTITY_TYPE_MDS,
                      force_new, proto, NULL, NULL);
     if (ret)
         return ERR_PTR(ret);
 
     return auth;
 }
 
 static int mds_add_authorizer_challenge(struct ceph_connection *con,
                     void *challenge_buf, int challenge_buf_len)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
     struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
 
     return ceph_auth_add_authorizer_challenge(ac, s->s_auth.authorizer,
                         challenge_buf, challenge_buf_len);
 }
 
 static int mds_verify_authorizer_reply(struct ceph_connection *con)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
     struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
     struct ceph_auth_handshake *auth = &s->s_auth;
 
     return ceph_auth_verify_authorizer_reply(ac, auth->authorizer,
         auth->authorizer_reply_buf, auth->authorizer_reply_buf_len,
         NULL, NULL, NULL, NULL);
 }
 
 static int mds_invalidate_authorizer(struct ceph_connection *con)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mds_client *mdsc = s->s_mdsc;
     struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
 
     ceph_auth_invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);
 
     return ceph_monc_validate_auth(&mdsc->fsc->client->monc);
 }
 
 static int mds_get_auth_request(struct ceph_connection *con,
                 void *buf, int *buf_len,
                 void **authorizer, int *authorizer_len)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
     struct ceph_auth_handshake *auth = &s->s_auth;
     int ret;
 
     ret = ceph_auth_get_authorizer(ac, auth, CEPH_ENTITY_TYPE_MDS,
                        buf, buf_len);
     if (ret)
         return ret;
 
     *authorizer = auth->authorizer_buf;
     *authorizer_len = auth->authorizer_buf_len;
     return 0;
 }
 
 static int mds_handle_auth_reply_more(struct ceph_connection *con,
                       void *reply, int reply_len,
                       void *buf, int *buf_len,
                       void **authorizer, int *authorizer_len)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
     struct ceph_auth_handshake *auth = &s->s_auth;
     int ret;
 
     ret = ceph_auth_handle_svc_reply_more(ac, auth, reply, reply_len,
                           buf, buf_len);
     if (ret)
         return ret;
 
     *authorizer = auth->authorizer_buf;
     *authorizer_len = auth->authorizer_buf_len;
     return 0;
 }
 
 static int mds_handle_auth_done(struct ceph_connection *con,
                 u64 global_id, void *reply, int reply_len,
                 u8 *session_key, int *session_key_len,
                 u8 *con_secret, int *con_secret_len)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_auth_client *ac = s->s_mdsc->fsc->client->monc.auth;
     struct ceph_auth_handshake *auth = &s->s_auth;
 
     return ceph_auth_handle_svc_reply_done(ac, auth, reply, reply_len,
                            session_key, session_key_len,
                            con_secret, con_secret_len);
 }
 
 static int mds_handle_auth_bad_method(struct ceph_connection *con,
                       int used_proto, int result,
                       const int *allowed_protos, int proto_cnt,
                       const int *allowed_modes, int mode_cnt)
 {
     struct ceph_mds_session *s = con->private;
     struct ceph_mon_client *monc = &s->s_mdsc->fsc->client->monc;
     int ret;
 
     if (ceph_auth_handle_bad_authorizer(monc->auth, CEPH_ENTITY_TYPE_MDS,
                         used_proto, result,
                         allowed_protos, proto_cnt,
                         allowed_modes, mode_cnt)) {
         ret = ceph_monc_validate_auth(monc);
         if (ret)
             return ret;
     }
 
     return -EACCES;
 }
 
 static struct ceph_msg *mds_alloc_msg(struct ceph_connection *con,
                 struct ceph_msg_header *hdr, int *skip)
 {
     struct ceph_msg *msg;
     int type = (int) le16_to_cpu(hdr->type);
     int front_len = (int) le32_to_cpu(hdr->front_len);
 
     if (con->in_msg)
         return con->in_msg;
 
     *skip = 0;
     msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
     if (!msg) {
         pr_err("unable to allocate msg type %d len %d\n",
                type, front_len);
         return NULL;
     }
 
     return msg;
 }
 
 static int mds_sign_message(struct ceph_msg *msg)
 {
        struct ceph_mds_session *s = msg->con->private;
        struct ceph_auth_handshake *auth = &s->s_auth;
 
        return ceph_auth_sign_message(auth, msg);
 }
 
 static int mds_check_message_signature(struct ceph_msg *msg)
 {
        struct ceph_mds_session *s = msg->con->private;
        struct ceph_auth_handshake *auth = &s->s_auth;
 
        return ceph_auth_check_message_signature(auth, msg);
 }
 
 static const struct ceph_connection_operations mds_con_ops = {
     .get = mds_get_con,
     .put = mds_put_con,
     .alloc_msg = mds_alloc_msg,
     .dispatch = mds_dispatch,
     .peer_reset = mds_peer_reset,
     .get_authorizer = mds_get_authorizer,
     .add_authorizer_challenge = mds_add_authorizer_challenge,
     .verify_authorizer_reply = mds_verify_authorizer_reply,
     .invalidate_authorizer = mds_invalidate_authorizer,
     .sign_message = mds_sign_message,
     .check_message_signature = mds_check_message_signature,
     .get_auth_request = mds_get_auth_request,
     .handle_auth_reply_more = mds_handle_auth_reply_more,
     .handle_auth_done = mds_handle_auth_done,
     .handle_auth_bad_method = mds_handle_auth_bad_method,
 };
 
 /* eof */