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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
 /*
  * linux/fs/lockd/svclock.c
  *
  * Handling of server-side locks, mostly of the blocked variety.
  * This is the ugliest part of lockd because we tread on very thin ice.
  * GRANT and CANCEL calls may get stuck, meet in mid-flight, etc.
  * IMNSHO introducing the grant callback into the NLM protocol was one
  * of the worst ideas Sun ever had. Except maybe for the idea of doing
  * NFS file locking at all.
  *
  * I'm trying hard to avoid race conditions by protecting most accesses
  * to a file's list of blocked locks through a semaphore. The global
  * list of blocked locks is not protected in this fashion however.
  * Therefore, some functions (such as the RPC callback for the async grant
  * call) move blocked locks towards the head of the list *while some other
  * process might be traversing it*. This should not be a problem in
  * practice, because this will only cause functions traversing the list
  * to visit some blocks twice.
  *
  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  */
 
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/svc_xprt.h>
 #include <linux/lockd/nlm.h>
 #include <linux/lockd/lockd.h>
 #include <linux/kthread.h>
 #include <linux/exportfs.h>
 
 #define NLMDBG_FACILITY     NLMDBG_SVCLOCK
 
 #ifdef CONFIG_LOCKD_V4
 #define nlm_deadlock    nlm4_deadlock
 #else
 #define nlm_deadlock    nlm_lck_denied
 #endif
 
 static void nlmsvc_release_block(struct nlm_block *block);
 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long);
 static void nlmsvc_remove_block(struct nlm_block *block);
 
 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock);
 static void nlmsvc_freegrantargs(struct nlm_rqst *call);
 static const struct rpc_call_ops nlmsvc_grant_ops;
 
 /*
  * The list of blocked locks to retry
  */
 static LIST_HEAD(nlm_blocked);
 static DEFINE_SPINLOCK(nlm_blocked_lock);
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
 {
     /*
      * We can get away with a static buffer because this is only called
      * from lockd, which is single-threaded.
      */
     static char buf[2*NLM_MAXCOOKIELEN+1];
     unsigned int i, len = sizeof(buf);
     char *p = buf;
 
     len--;  /* allow for trailing \0 */
     if (len < 3)
         return "???";
     for (i = 0 ; i < cookie->len ; i++) {
         if (len < 2) {
             strcpy(p-3, "...");
             break;
         }
         sprintf(p, "%02x", cookie->data[i]);
         p += 2;
         len -= 2;
     }
     *p = '\0';
 
     return buf;
 }
 #endif
 
 /*
  * Insert a blocked lock into the global list
  */
 static void
 nlmsvc_insert_block_locked(struct nlm_block *block, unsigned long when)
 {
     struct nlm_block *b;
     struct list_head *pos;
 
     dprintk("lockd: nlmsvc_insert_block(%p, %ld)\n", block, when);
     if (list_empty(&block->b_list)) {
         kref_get(&block->b_count);
     } else {
         list_del_init(&block->b_list);
     }
 
     pos = &nlm_blocked;
     if (when != NLM_NEVER) {
         if ((when += jiffies) == NLM_NEVER)
             when ++;
         list_for_each(pos, &nlm_blocked) {
             b = list_entry(pos, struct nlm_block, b_list);
             if (time_after(b->b_when,when) || b->b_when == NLM_NEVER)
                 break;
         }
         /* On normal exit from the loop, pos == &nlm_blocked,
          * so we will be adding to the end of the list - good
          */
     }
 
     list_add_tail(&block->b_list, pos);
     block->b_when = when;
 }
 
 static void nlmsvc_insert_block(struct nlm_block *block, unsigned long when)
 {
     spin_lock(&nlm_blocked_lock);
     nlmsvc_insert_block_locked(block, when);
     spin_unlock(&nlm_blocked_lock);
 }
 
 /*
  * Remove a block from the global list
  */
 static inline void
 nlmsvc_remove_block(struct nlm_block *block)
 {
     if (!list_empty(&block->b_list)) {
         spin_lock(&nlm_blocked_lock);
         list_del_init(&block->b_list);
         spin_unlock(&nlm_blocked_lock);
         nlmsvc_release_block(block);
     }
 }
 
 /*
  * Find a block for a given lock
  */
 static struct nlm_block *
 nlmsvc_lookup_block(struct nlm_file *file, struct nlm_lock *lock)
 {
     struct nlm_block    *block;
     struct file_lock    *fl;
 
     dprintk("lockd: nlmsvc_lookup_block f=%p pd=%d %Ld-%Ld ty=%d\n",
                 file, lock->fl.fl_pid,
                 (long long)lock->fl.fl_start,
                 (long long)lock->fl.fl_end, lock->fl.fl_type);
     list_for_each_entry(block, &nlm_blocked, b_list) {
         fl = &block->b_call->a_args.lock.fl;
         dprintk("lockd: check f=%p pd=%d %Ld-%Ld ty=%d cookie=%s\n",
                 block->b_file, fl->fl_pid,
                 (long long)fl->fl_start,
                 (long long)fl->fl_end, fl->fl_type,
                 nlmdbg_cookie2a(&block->b_call->a_args.cookie));
         if (block->b_file == file && nlm_compare_locks(fl, &lock->fl)) {
             kref_get(&block->b_count);
             return block;
         }
     }
 
     return NULL;
 }
 
 static inline int nlm_cookie_match(struct nlm_cookie *a, struct nlm_cookie *b)
 {
     if (a->len != b->len)
         return 0;
     if (memcmp(a->data, b->data, a->len))
         return 0;
     return 1;
 }
 
 /*
  * Find a block with a given NLM cookie.
  */
 static inline struct nlm_block *
 nlmsvc_find_block(struct nlm_cookie *cookie)
 {
     struct nlm_block *block;
 
     list_for_each_entry(block, &nlm_blocked, b_list) {
         if (nlm_cookie_match(&block->b_call->a_args.cookie,cookie))
             goto found;
     }
 
     return NULL;
 
 found:
     dprintk("nlmsvc_find_block(%s): block=%p\n", nlmdbg_cookie2a(cookie), block);
     kref_get(&block->b_count);
     return block;
 }
 
 /*
  * Create a block and initialize it.
  *
  * Note: we explicitly set the cookie of the grant reply to that of
  * the blocked lock request. The spec explicitly mentions that the client
  * should _not_ rely on the callback containing the same cookie as the
  * request, but (as I found out later) that's because some implementations
  * do just this. Never mind the standards comittees, they support our
  * logging industries.
  *
  * 10 years later: I hope we can safely ignore these old and broken
  * clients by now. Let's fix this so we can uniquely identify an incoming
  * GRANTED_RES message by cookie, without having to rely on the client's IP
  * address. --okir
  */
 static struct nlm_block *
 nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
             struct nlm_file *file, struct nlm_lock *lock,
             struct nlm_cookie *cookie)
 {
     struct nlm_block    *block;
     struct nlm_rqst     *call = NULL;
 
     call = nlm_alloc_call(host);
     if (call == NULL)
         return NULL;
 
     /* Allocate memory for block, and initialize arguments */
     block = kzalloc(sizeof(*block), GFP_KERNEL);
     if (block == NULL)
         goto failed;
     kref_init(&block->b_count);
     INIT_LIST_HEAD(&block->b_list);
     INIT_LIST_HEAD(&block->b_flist);
 
     if (!nlmsvc_setgrantargs(call, lock))
         goto failed_free;
 
     /* Set notifier function for VFS, and init args */
     call->a_args.lock.fl.fl_flags |= FL_SLEEP;
     call->a_args.lock.fl.fl_lmops = &nlmsvc_lock_operations;
     nlmclnt_next_cookie(&call->a_args.cookie);
 
     dprintk("lockd: created block %p...\n", block);
 
     /* Create and initialize the block */
     block->b_daemon = rqstp->rq_server;
     block->b_host   = host;
     block->b_file   = file;
     file->f_count++;
 
     /* Add to file's list of blocks */
     list_add(&block->b_flist, &file->f_blocks);
 
     /* Set up RPC arguments for callback */
     block->b_call = call;
     call->a_flags   = RPC_TASK_ASYNC;
     call->a_block = block;
 
     return block;
 
 failed_free:
     kfree(block);
 failed:
     nlmsvc_release_call(call);
     return NULL;
 }
 
 /*
  * Delete a block.
  * It is the caller's responsibility to check whether the file
  * can be closed hereafter.
  */
 static int nlmsvc_unlink_block(struct nlm_block *block)
 {
     int status;
     dprintk("lockd: unlinking block %p...\n", block);
 
     /* Remove block from list */
     status = locks_delete_block(&block->b_call->a_args.lock.fl);
     nlmsvc_remove_block(block);
     return status;
 }
 
 static void nlmsvc_free_block(struct kref *kref)
 {
     struct nlm_block *block = container_of(kref, struct nlm_block, b_count);
     struct nlm_file     *file = block->b_file;
 
     dprintk("lockd: freeing block %p...\n", block);
 
     /* Remove block from file's list of blocks */
     list_del_init(&block->b_flist);
     mutex_unlock(&file->f_mutex);
 
     nlmsvc_freegrantargs(block->b_call);
     nlmsvc_release_call(block->b_call);
     nlm_release_file(block->b_file);
     kfree(block);
 }
 
 static void nlmsvc_release_block(struct nlm_block *block)
 {
     if (block != NULL)
         kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
 }
 
 /*
  * Loop over all blocks and delete blocks held by
  * a matching host.
  */
 void nlmsvc_traverse_blocks(struct nlm_host *host,
             struct nlm_file *file,
             nlm_host_match_fn_t match)
 {
     struct nlm_block *block, *next;
 
 restart:
     mutex_lock(&file->f_mutex);
     list_for_each_entry_safe(block, next, &file->f_blocks, b_flist) {
         if (!match(block->b_host, host))
             continue;
         /* Do not destroy blocks that are not on
          * the global retry list - why? */
         if (list_empty(&block->b_list))
             continue;
         kref_get(&block->b_count);
         mutex_unlock(&file->f_mutex);
         nlmsvc_unlink_block(block);
         nlmsvc_release_block(block);
         goto restart;
     }
     mutex_unlock(&file->f_mutex);
 }
 
 static struct nlm_lockowner *
 nlmsvc_get_lockowner(struct nlm_lockowner *lockowner)
 {
     refcount_inc(&lockowner->count);
     return lockowner;
 }
 
 void nlmsvc_put_lockowner(struct nlm_lockowner *lockowner)
 {
     if (!refcount_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
         return;
     list_del(&lockowner->list);
     spin_unlock(&lockowner->host->h_lock);
     nlmsvc_release_host(lockowner->host);
     kfree(lockowner);
 }
 
 static struct nlm_lockowner *__nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
 {
     struct nlm_lockowner *lockowner;
     list_for_each_entry(lockowner, &host->h_lockowners, list) {
         if (lockowner->pid != pid)
             continue;
         return nlmsvc_get_lockowner(lockowner);
     }
     return NULL;
 }
 
 static struct nlm_lockowner *nlmsvc_find_lockowner(struct nlm_host *host, pid_t pid)
 {
     struct nlm_lockowner *res, *new = NULL;
 
     spin_lock(&host->h_lock);
     res = __nlmsvc_find_lockowner(host, pid);
 
     if (res == NULL) {
         spin_unlock(&host->h_lock);
         new = kmalloc(sizeof(*res), GFP_KERNEL);
         spin_lock(&host->h_lock);
         res = __nlmsvc_find_lockowner(host, pid);
         if (res == NULL && new != NULL) {
             res = new;
             /* fs/locks.c will manage the refcount through lock_ops */
             refcount_set(&new->count, 1);
             new->pid = pid;
             new->host = nlm_get_host(host);
             list_add(&new->list, &host->h_lockowners);
             new = NULL;
         }
     }
 
     spin_unlock(&host->h_lock);
     kfree(new);
     return res;
 }
 
 void
 nlmsvc_release_lockowner(struct nlm_lock *lock)
 {
     if (lock->fl.fl_owner)
         nlmsvc_put_lockowner(lock->fl.fl_owner);
 }
 
 void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host,
                         pid_t pid)
 {
     fl->fl_owner = nlmsvc_find_lockowner(host, pid);
 }
 
 /*
  * Initialize arguments for GRANTED call. The nlm_rqst structure
  * has been cleared already.
  */
 static int nlmsvc_setgrantargs(struct nlm_rqst *call, struct nlm_lock *lock)
 {
     locks_copy_lock(&call->a_args.lock.fl, &lock->fl);
     memcpy(&call->a_args.lock.fh, &lock->fh, sizeof(call->a_args.lock.fh));
     call->a_args.lock.caller = utsname()->nodename;
     call->a_args.lock.oh.len = lock->oh.len;
 
     /* set default data area */
     call->a_args.lock.oh.data = call->a_owner;
     call->a_args.lock.svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
 
     if (lock->oh.len > NLMCLNT_OHSIZE) {
         void *data = kmalloc(lock->oh.len, GFP_KERNEL);
         if (!data)
             return 0;
         call->a_args.lock.oh.data = (u8 *) data;
     }
 
     memcpy(call->a_args.lock.oh.data, lock->oh.data, lock->oh.len);
     return 1;
 }
 
 static void nlmsvc_freegrantargs(struct nlm_rqst *call)
 {
     if (call->a_args.lock.oh.data != call->a_owner)
         kfree(call->a_args.lock.oh.data);
 
     locks_release_private(&call->a_args.lock.fl);
 }
 
 /*
  * Deferred lock request handling for non-blocking lock
  */
 static __be32
 nlmsvc_defer_lock_rqst(struct svc_rqst *rqstp, struct nlm_block *block)
 {
     __be32 status = nlm_lck_denied_nolocks;
 
     block->b_flags |= B_QUEUED;
 
     nlmsvc_insert_block(block, NLM_TIMEOUT);
 
     block->b_cache_req = &rqstp->rq_chandle;
     if (rqstp->rq_chandle.defer) {
         block->b_deferred_req =
             rqstp->rq_chandle.defer(block->b_cache_req);
         if (block->b_deferred_req != NULL)
             status = nlm_drop_reply;
     }
     dprintk("lockd: nlmsvc_defer_lock_rqst block %p flags %d status %d\n",
         block, block->b_flags, ntohl(status));
 
     return status;
 }
 
 /*
  * Attempt to establish a lock, and if it can't be granted, block it
  * if required.
  */
 __be32
 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
         struct nlm_host *host, struct nlm_lock *lock, int wait,
         struct nlm_cookie *cookie, int reclaim)
 {
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
     struct inode        *inode = nlmsvc_file_inode(file);
 #endif
     struct nlm_block    *block = NULL;
     int         error;
     int         mode;
     int         async_block = 0;
     __be32          ret;
 
     dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
                 inode->i_sb->s_id, inode->i_ino,
                 lock->fl.fl_type, lock->fl.fl_pid,
                 (long long)lock->fl.fl_start,
                 (long long)lock->fl.fl_end,
                 wait);
 
     if (nlmsvc_file_file(file)->f_op->lock) {
         async_block = wait;
         wait = 0;
     }
 
     /* Lock file against concurrent access */
     mutex_lock(&file->f_mutex);
     /* Get existing block (in case client is busy-waiting)
      * or create new block
      */
     block = nlmsvc_lookup_block(file, lock);
     if (block == NULL) {
         block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
         ret = nlm_lck_denied_nolocks;
         if (block == NULL)
             goto out;
         lock = &block->b_call->a_args.lock;
     } else
         lock->fl.fl_flags &= ~FL_SLEEP;
 
     if (block->b_flags & B_QUEUED) {
         dprintk("lockd: nlmsvc_lock deferred block %p flags %d\n",
                             block, block->b_flags);
         if (block->b_granted) {
             nlmsvc_unlink_block(block);
             ret = nlm_granted;
             goto out;
         }
         if (block->b_flags & B_TIMED_OUT) {
             nlmsvc_unlink_block(block);
             ret = nlm_lck_denied;
             goto out;
         }
         ret = nlm_drop_reply;
         goto out;
     }
 
     if (locks_in_grace(SVC_NET(rqstp)) && !reclaim) {
         ret = nlm_lck_denied_grace_period;
         goto out;
     }
     if (reclaim && !locks_in_grace(SVC_NET(rqstp))) {
         ret = nlm_lck_denied_grace_period;
         goto out;
     }
 
     if (!wait)
         lock->fl.fl_flags &= ~FL_SLEEP;
     mode = lock_to_openmode(&lock->fl);
     error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
     lock->fl.fl_flags &= ~FL_SLEEP;
 
     dprintk("lockd: vfs_lock_file returned %d\n", error);
     switch (error) {
         case 0:
             ret = nlm_granted;
             goto out;
         case -EAGAIN:
             /*
              * If this is a blocking request for an
              * already pending lock request then we need
              * to put it back on lockd's block list
              */
             if (wait)
                 break;
             ret = async_block ? nlm_lck_blocked : nlm_lck_denied;
             goto out;
         case FILE_LOCK_DEFERRED:
             if (wait)
                 break;
             /* Filesystem lock operation is in progress
                Add it to the queue waiting for callback */
             ret = nlmsvc_defer_lock_rqst(rqstp, block);
             goto out;
         case -EDEADLK:
             ret = nlm_deadlock;
             goto out;
         default:            /* includes ENOLCK */
             ret = nlm_lck_denied_nolocks;
             goto out;
     }
 
     ret = nlm_lck_blocked;
 
     /* Append to list of blocked */
     nlmsvc_insert_block(block, NLM_NEVER);
 out:
     mutex_unlock(&file->f_mutex);
     nlmsvc_release_block(block);
     dprintk("lockd: nlmsvc_lock returned %u\n", ret);
     return ret;
 }
 
 /*
  * Test for presence of a conflicting lock.
  */
 __be32
 nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
         struct nlm_host *host, struct nlm_lock *lock,
         struct nlm_lock *conflock, struct nlm_cookie *cookie)
 {
     int         error;
     int         mode;
     __be32          ret;
 
     dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
                 nlmsvc_file_inode(file)->i_sb->s_id,
                 nlmsvc_file_inode(file)->i_ino,
                 lock->fl.fl_type,
                 (long long)lock->fl.fl_start,
                 (long long)lock->fl.fl_end);
 
     if (locks_in_grace(SVC_NET(rqstp))) {
         ret = nlm_lck_denied_grace_period;
         goto out;
     }
 
     mode = lock_to_openmode(&lock->fl);
     error = vfs_test_lock(file->f_file[mode], &lock->fl);
     if (error) {
         /* We can't currently deal with deferred test requests */
         if (error == FILE_LOCK_DEFERRED)
             WARN_ON_ONCE(1);
 
         ret = nlm_lck_denied_nolocks;
         goto out;
     }
 
     if (lock->fl.fl_type == F_UNLCK) {
         ret = nlm_granted;
         goto out;
     }
 
     dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
         lock->fl.fl_type, (long long)lock->fl.fl_start,
         (long long)lock->fl.fl_end);
     conflock->caller = "somehost";  /* FIXME */
     conflock->len = strlen(conflock->caller);
     conflock->oh.len = 0;       /* don't return OH info */
     conflock->svid = lock->fl.fl_pid;
     conflock->fl.fl_type = lock->fl.fl_type;
     conflock->fl.fl_start = lock->fl.fl_start;
     conflock->fl.fl_end = lock->fl.fl_end;
     locks_release_private(&lock->fl);
 
     ret = nlm_lck_denied;
 out:
     return ret;
 }
 
 /*
  * Remove a lock.
  * This implies a CANCEL call: We send a GRANT_MSG, the client replies
  * with a GRANT_RES call which gets lost, and calls UNLOCK immediately
  * afterwards. In this case the block will still be there, and hence
  * must be removed.
  */
 __be32
 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 {
     int error = 0;
 
     dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
                 nlmsvc_file_inode(file)->i_sb->s_id,
                 nlmsvc_file_inode(file)->i_ino,
                 lock->fl.fl_pid,
                 (long long)lock->fl.fl_start,
                 (long long)lock->fl.fl_end);
 
     /* First, cancel any lock that might be there */
     nlmsvc_cancel_blocked(net, file, lock);
 
     lock->fl.fl_type = F_UNLCK;
     if (file->f_file[O_RDONLY])
         error = vfs_lock_file(file->f_file[O_RDONLY], F_SETLK,
                     &lock->fl, NULL);
     if (file->f_file[O_WRONLY])
         error = vfs_lock_file(file->f_file[O_WRONLY], F_SETLK,
                     &lock->fl, NULL);
 
     return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 }
 
 /*
  * Cancel a previously blocked request.
  *
  * A cancel request always overrides any grant that may currently
  * be in progress.
  * The calling procedure must check whether the file can be closed.
  */
 __be32
 nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 {
     struct nlm_block    *block;
     int status = 0;
     int mode;
 
     dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
                 nlmsvc_file_inode(file)->i_sb->s_id,
                 nlmsvc_file_inode(file)->i_ino,
                 lock->fl.fl_pid,
                 (long long)lock->fl.fl_start,
                 (long long)lock->fl.fl_end);
 
     if (locks_in_grace(net))
         return nlm_lck_denied_grace_period;
 
     mutex_lock(&file->f_mutex);
     block = nlmsvc_lookup_block(file, lock);
     mutex_unlock(&file->f_mutex);
     if (block != NULL) {
         mode = lock_to_openmode(&lock->fl);
         vfs_cancel_lock(block->b_file->f_file[mode],
                 &block->b_call->a_args.lock.fl);
         status = nlmsvc_unlink_block(block);
         nlmsvc_release_block(block);
     }
     return status ? nlm_lck_denied : nlm_granted;
 }
 
 /*
  * This is a callback from the filesystem for VFS file lock requests.
  * It will be used if lm_grant is defined and the filesystem can not
  * respond to the request immediately.
  * For SETLK or SETLKW request it will get the local posix lock.
  * In all cases it will move the block to the head of nlm_blocked q where
  * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
  * deferred rpc for GETLK and SETLK.
  */
 static void
 nlmsvc_update_deferred_block(struct nlm_block *block, int result)
 {
     block->b_flags |= B_GOT_CALLBACK;
     if (result == 0)
         block->b_granted = 1;
     else
         block->b_flags |= B_TIMED_OUT;
 }
 
 static int nlmsvc_grant_deferred(struct file_lock *fl, int result)
 {
     struct nlm_block *block;
     int rc = -ENOENT;
 
     spin_lock(&nlm_blocked_lock);
     list_for_each_entry(block, &nlm_blocked, b_list) {
         if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
             dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n",
                             block, block->b_flags);
             if (block->b_flags & B_QUEUED) {
                 if (block->b_flags & B_TIMED_OUT) {
                     rc = -ENOLCK;
                     break;
                 }
                 nlmsvc_update_deferred_block(block, result);
             } else if (result == 0)
                 block->b_granted = 1;
 
             nlmsvc_insert_block_locked(block, 0);
             svc_wake_up(block->b_daemon);
             rc = 0;
             break;
         }
     }
     spin_unlock(&nlm_blocked_lock);
     if (rc == -ENOENT)
         printk(KERN_WARNING "lockd: grant for unknown block\n");
     return rc;
 }
 
 /*
  * Unblock a blocked lock request. This is a callback invoked from the
  * VFS layer when a lock on which we blocked is removed.
  *
  * This function doesn't grant the blocked lock instantly, but rather moves
  * the block to the head of nlm_blocked where it can be picked up by lockd.
  */
 static void
 nlmsvc_notify_blocked(struct file_lock *fl)
 {
     struct nlm_block    *block;
 
     dprintk("lockd: VFS unblock notification for block %p\n", fl);
     spin_lock(&nlm_blocked_lock);
     list_for_each_entry(block, &nlm_blocked, b_list) {
         if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) {
             nlmsvc_insert_block_locked(block, 0);
             spin_unlock(&nlm_blocked_lock);
             svc_wake_up(block->b_daemon);
             return;
         }
     }
     spin_unlock(&nlm_blocked_lock);
     printk(KERN_WARNING "lockd: notification for unknown block!\n");
 }
 
 static fl_owner_t nlmsvc_get_owner(fl_owner_t owner)
 {
     return nlmsvc_get_lockowner(owner);
 }
 
 static void nlmsvc_put_owner(fl_owner_t owner)
 {
     nlmsvc_put_lockowner(owner);
 }
 
 const struct lock_manager_operations nlmsvc_lock_operations = {
     .lm_notify = nlmsvc_notify_blocked,
     .lm_grant = nlmsvc_grant_deferred,
     .lm_get_owner = nlmsvc_get_owner,
     .lm_put_owner = nlmsvc_put_owner,
 };
 
 /*
  * Try to claim a lock that was previously blocked.
  *
  * Note that we use both the RPC_GRANTED_MSG call _and_ an async
  * RPC thread when notifying the client. This seems like overkill...
  * Here's why:
  *  -   we don't want to use a synchronous RPC thread, otherwise
  *  we might find ourselves hanging on a dead portmapper.
  *  -   Some lockd implementations (e.g. HP) don't react to
  *  RPC_GRANTED calls; they seem to insist on RPC_GRANTED_MSG calls.
  */
 static void
 nlmsvc_grant_blocked(struct nlm_block *block)
 {
     struct nlm_file     *file = block->b_file;
     struct nlm_lock     *lock = &block->b_call->a_args.lock;
     int         mode;
     int         error;
     loff_t          fl_start, fl_end;
 
     dprintk("lockd: grant blocked lock %p\n", block);
 
     kref_get(&block->b_count);
 
     /* Unlink block request from list */
     nlmsvc_unlink_block(block);
 
     /* If b_granted is true this means we've been here before.
      * Just retry the grant callback, possibly refreshing the RPC
      * binding */
     if (block->b_granted) {
         nlm_rebind_host(block->b_host);
         goto callback;
     }
 
     /* Try the lock operation again */
     /* vfs_lock_file() can mangle fl_start and fl_end, but we need
      * them unchanged for the GRANT_MSG
      */
     lock->fl.fl_flags |= FL_SLEEP;
     fl_start = lock->fl.fl_start;
     fl_end = lock->fl.fl_end;
     mode = lock_to_openmode(&lock->fl);
     error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
     lock->fl.fl_flags &= ~FL_SLEEP;
     lock->fl.fl_start = fl_start;
     lock->fl.fl_end = fl_end;
 
     switch (error) {
     case 0:
         break;
     case FILE_LOCK_DEFERRED:
         dprintk("lockd: lock still blocked error %d\n", error);
         nlmsvc_insert_block(block, NLM_NEVER);
         nlmsvc_release_block(block);
         return;
     default:
         printk(KERN_WARNING "lockd: unexpected error %d in %s!\n",
                 -error, __func__);
         nlmsvc_insert_block(block, 10 * HZ);
         nlmsvc_release_block(block);
         return;
     }
 
 callback:
     /* Lock was granted by VFS. */
     dprintk("lockd: GRANTing blocked lock.\n");
     block->b_granted = 1;
 
     /* keep block on the list, but don't reattempt until the RPC
      * completes or the submission fails
      */
     nlmsvc_insert_block(block, NLM_NEVER);
 
     /* Call the client -- use a soft RPC task since nlmsvc_retry_blocked
      * will queue up a new one if this one times out
      */
     error = nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG,
                 &nlmsvc_grant_ops);
 
     /* RPC submission failed, wait a bit and retry */
     if (error < 0)
         nlmsvc_insert_block(block, 10 * HZ);
 }
 
 /*
  * This is the callback from the RPC layer when the NLM_GRANTED_MSG
  * RPC call has succeeded or timed out.
  * Like all RPC callbacks, it is invoked by the rpciod process, so it
  * better not sleep. Therefore, we put the blocked lock on the nlm_blocked
  * chain once more in order to have it removed by lockd itself (which can
  * then sleep on the file semaphore without disrupting e.g. the nfs client).
  */
 static void nlmsvc_grant_callback(struct rpc_task *task, void *data)
 {
     struct nlm_rqst     *call = data;
     struct nlm_block    *block = call->a_block;
     unsigned long       timeout;
 
     dprintk("lockd: GRANT_MSG RPC callback\n");
 
     spin_lock(&nlm_blocked_lock);
     /* if the block is not on a list at this point then it has
      * been invalidated. Don't try to requeue it.
      *
      * FIXME: it's possible that the block is removed from the list
      * after this check but before the nlmsvc_insert_block. In that
      * case it will be added back. Perhaps we need better locking
      * for nlm_blocked?
      */
     if (list_empty(&block->b_list))
         goto out;
 
     /* Technically, we should down the file semaphore here. Since we
      * move the block towards the head of the queue only, no harm
      * can be done, though. */
     if (task->tk_status < 0) {
         /* RPC error: Re-insert for retransmission */
         timeout = 10 * HZ;
     } else {
         /* Call was successful, now wait for client callback */
         timeout = 60 * HZ;
     }
     nlmsvc_insert_block_locked(block, timeout);
     svc_wake_up(block->b_daemon);
 out:
     spin_unlock(&nlm_blocked_lock);
 }
 
 /*
  * FIXME: nlmsvc_release_block() grabs a mutex.  This is not allowed for an
  * .rpc_release rpc_call_op
  */
 static void nlmsvc_grant_release(void *data)
 {
     struct nlm_rqst     *call = data;
     nlmsvc_release_block(call->a_block);
 }
 
 static const struct rpc_call_ops nlmsvc_grant_ops = {
     .rpc_call_done = nlmsvc_grant_callback,
     .rpc_release = nlmsvc_grant_release,
 };
 
 /*
  * We received a GRANT_RES callback. Try to find the corresponding
  * block.
  */
 void
 nlmsvc_grant_reply(struct nlm_cookie *cookie, __be32 status)
 {
     struct nlm_block    *block;
 
     dprintk("grant_reply: looking for cookie %x, s=%d \n",
         *(unsigned int *)(cookie->data), status);
     if (!(block = nlmsvc_find_block(cookie)))
         return;
 
     if (status == nlm_lck_denied_grace_period) {
         /* Try again in a couple of seconds */
         nlmsvc_insert_block(block, 10 * HZ);
     } else {
         /*
          * Lock is now held by client, or has been rejected.
          * In both cases, the block should be removed.
          */
         nlmsvc_unlink_block(block);
     }
     nlmsvc_release_block(block);
 }
 
 /* Helper function to handle retry of a deferred block.
  * If it is a blocking lock, call grant_blocked.
  * For a non-blocking lock or test lock, revisit the request.
  */
 static void
 retry_deferred_block(struct nlm_block *block)
 {
     if (!(block->b_flags & B_GOT_CALLBACK))
         block->b_flags |= B_TIMED_OUT;
     nlmsvc_insert_block(block, NLM_TIMEOUT);
     dprintk("revisit block %p flags %d\n",  block, block->b_flags);
     if (block->b_deferred_req) {
         block->b_deferred_req->revisit(block->b_deferred_req, 0);
         block->b_deferred_req = NULL;
     }
 }
 
 /*
  * Retry all blocked locks that have been notified. This is where lockd
  * picks up locks that can be granted, or grant notifications that must
  * be retransmitted.
  */
 unsigned long
 nlmsvc_retry_blocked(void)
 {
     unsigned long   timeout = MAX_SCHEDULE_TIMEOUT;
     struct nlm_block *block;
 
     spin_lock(&nlm_blocked_lock);
     while (!list_empty(&nlm_blocked) && !kthread_should_stop()) {
         block = list_entry(nlm_blocked.next, struct nlm_block, b_list);
 
         if (block->b_when == NLM_NEVER)
             break;
         if (time_after(block->b_when, jiffies)) {
             timeout = block->b_when - jiffies;
             break;
         }
         spin_unlock(&nlm_blocked_lock);
 
         dprintk("nlmsvc_retry_blocked(%p, when=%ld)\n",
             block, block->b_when);
         if (block->b_flags & B_QUEUED) {
             dprintk("nlmsvc_retry_blocked delete block (%p, granted=%d, flags=%d)\n",
                 block, block->b_granted, block->b_flags);
             retry_deferred_block(block);
         } else
             nlmsvc_grant_blocked(block);
         spin_lock(&nlm_blocked_lock);
     }
     spin_unlock(&nlm_blocked_lock);
 
     return timeout;
 }

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