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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-or-later
 /*
  * Network block device - make block devices work over TCP
  *
  * Note that you can not swap over this thing, yet. Seems to work but
  * deadlocks sometimes - you can not swap over TCP in general.
  * 
  * Copyright 1997-2000, 2008 Pavel Machek <pavel@ucw.cz>
  * Parts copyright 2001 Steven Whitehouse <steve@chygwyn.com>
  *
  * (part of code stolen from loop.c)
  */
 
 #define pr_fmt(fmt) "nbd: " fmt
 
 #include <linux/major.h>
 
 #include <linux/blkdev.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/sched/mm.h>
 #include <linux/fs.h>
 #include <linux/bio.h>
 #include <linux/stat.h>
 #include <linux/errno.h>
 #include <linux/file.h>
 #include <linux/ioctl.h>
 #include <linux/mutex.h>
 #include <linux/compiler.h>
 #include <linux/completion.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <net/sock.h>
 #include <linux/net.h>
 #include <linux/kthread.h>
 #include <linux/types.h>
 #include <linux/debugfs.h>
 #include <linux/blk-mq.h>
 
 #include <linux/uaccess.h>
 #include <asm/types.h>
 
 #include <linux/nbd.h>
 #include <linux/nbd-netlink.h>
 #include <net/genetlink.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nbd.h>
 
 static DEFINE_IDR(nbd_index_idr);
 static DEFINE_MUTEX(nbd_index_mutex);
 static struct workqueue_struct *nbd_del_wq;
 static int nbd_total_devices = 0;
 
 struct nbd_sock {
     struct socket *sock;
     struct mutex tx_lock;
     struct request *pending;
     int sent;
     bool dead;
     int fallback_index;
     int cookie;
 };
 
 struct recv_thread_args {
     struct work_struct work;
     struct nbd_device *nbd;
     int index;
 };
 
 struct link_dead_args {
     struct work_struct work;
     int index;
 };
 
 #define NBD_RT_TIMEDOUT         0
 #define NBD_RT_DISCONNECT_REQUESTED 1
 #define NBD_RT_DISCONNECTED     2
 #define NBD_RT_HAS_PID_FILE     3
 #define NBD_RT_HAS_CONFIG_REF       4
 #define NBD_RT_BOUND            5
 #define NBD_RT_DISCONNECT_ON_CLOSE  6
 #define NBD_RT_HAS_BACKEND_FILE     7
 
 #define NBD_DESTROY_ON_DISCONNECT   0
 #define NBD_DISCONNECT_REQUESTED    1
 
 struct nbd_config {
     u32 flags;
     unsigned long runtime_flags;
     u64 dead_conn_timeout;
 
     struct nbd_sock **socks;
     int num_connections;
     atomic_t live_connections;
     wait_queue_head_t conn_wait;
 
     atomic_t recv_threads;
     wait_queue_head_t recv_wq;
     unsigned int blksize_bits;
     loff_t bytesize;
 #if IS_ENABLED(CONFIG_DEBUG_FS)
     struct dentry *dbg_dir;
 #endif
 };
 
 static inline unsigned int nbd_blksize(struct nbd_config *config)
 {
     return 1u << config->blksize_bits;
 }
 
 struct nbd_device {
     struct blk_mq_tag_set tag_set;
 
     int index;
     refcount_t config_refs;
     refcount_t refs;
     struct nbd_config *config;
     struct mutex config_lock;
     struct gendisk *disk;
     struct workqueue_struct *recv_workq;
     struct work_struct remove_work;
 
     struct list_head list;
     struct task_struct *task_setup;
 
     unsigned long flags;
     pid_t pid; /* pid of nbd-client, if attached */
 
     char *backend;
 };
 
 #define NBD_CMD_REQUEUED    1
 /*
  * This flag will be set if nbd_queue_rq() succeed, and will be checked and
  * cleared in completion. Both setting and clearing of the flag are protected
  * by cmd->lock.
  */
 #define NBD_CMD_INFLIGHT    2
 
 struct nbd_cmd {
     struct nbd_device *nbd;
     struct mutex lock;
     int index;
     int cookie;
     int retries;
     blk_status_t status;
     unsigned long flags;
     u32 cmd_cookie;
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 static struct dentry *nbd_dbg_dir;
 #endif
 
 #define nbd_name(nbd) ((nbd)->disk->disk_name)
 
 #define NBD_MAGIC 0x68797548
 
 #define NBD_DEF_BLKSIZE_BITS 10
 
 static unsigned int nbds_max = 16;
 static int max_part = 16;
 static int part_shift;
 
 static int nbd_dev_dbg_init(struct nbd_device *nbd);
 static void nbd_dev_dbg_close(struct nbd_device *nbd);
 static void nbd_config_put(struct nbd_device *nbd);
 static void nbd_connect_reply(struct genl_info *info, int index);
 static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info);
 static void nbd_dead_link_work(struct work_struct *work);
 static void nbd_disconnect_and_put(struct nbd_device *nbd);
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
     return disk_to_dev(nbd->disk);
 }
 
 static void nbd_requeue_cmd(struct nbd_cmd *cmd)
 {
     struct request *req = blk_mq_rq_from_pdu(cmd);
 
     if (!test_and_set_bit(NBD_CMD_REQUEUED, &cmd->flags))
         blk_mq_requeue_request(req, true);
 }
 
 #define NBD_COOKIE_BITS 32
 
 static u64 nbd_cmd_handle(struct nbd_cmd *cmd)
 {
     struct request *req = blk_mq_rq_from_pdu(cmd);
     u32 tag = blk_mq_unique_tag(req);
     u64 cookie = cmd->cmd_cookie;
 
     return (cookie << NBD_COOKIE_BITS) | tag;
 }
 
 static u32 nbd_handle_to_tag(u64 handle)
 {
     return (u32)handle;
 }
 
 static u32 nbd_handle_to_cookie(u64 handle)
 {
     return (u32)(handle >> NBD_COOKIE_BITS);
 }
 
 static const char *nbdcmd_to_ascii(int cmd)
 {
     switch (cmd) {
     case  NBD_CMD_READ: return "read";
     case NBD_CMD_WRITE: return "write";
     case  NBD_CMD_DISC: return "disconnect";
     case NBD_CMD_FLUSH: return "flush";
     case  NBD_CMD_TRIM: return "trim/discard";
     }
     return "invalid";
 }
 
 static ssize_t pid_show(struct device *dev,
             struct device_attribute *attr, char *buf)
 {
     struct gendisk *disk = dev_to_disk(dev);
     struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
 
     return sprintf(buf, "%d\n", nbd->pid);
 }
 
 static const struct device_attribute pid_attr = {
     .attr = { .name = "pid", .mode = 0444},
     .show = pid_show,
 };
 
 static ssize_t backend_show(struct device *dev,
         struct device_attribute *attr, char *buf)
 {
     struct gendisk *disk = dev_to_disk(dev);
     struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
 
     return sprintf(buf, "%s\n", nbd->backend ?: "");
 }
 
 static const struct device_attribute backend_attr = {
     .attr = { .name = "backend", .mode = 0444},
     .show = backend_show,
 };
 
 static void nbd_dev_remove(struct nbd_device *nbd)
 {
     struct gendisk *disk = nbd->disk;
 
     del_gendisk(disk);
     put_disk(disk);
     blk_mq_free_tag_set(&nbd->tag_set);
 
     /*
      * Remove from idr after del_gendisk() completes, so if the same ID is
      * reused, the following add_disk() will succeed.
      */
     mutex_lock(&nbd_index_mutex);
     idr_remove(&nbd_index_idr, nbd->index);
     mutex_unlock(&nbd_index_mutex);
     destroy_workqueue(nbd->recv_workq);
     kfree(nbd);
 }
 
 static void nbd_dev_remove_work(struct work_struct *work)
 {
     nbd_dev_remove(container_of(work, struct nbd_device, remove_work));
 }
 
 static void nbd_put(struct nbd_device *nbd)
 {
     if (!refcount_dec_and_test(&nbd->refs))
         return;
 
     /* Call del_gendisk() asynchrounously to prevent deadlock */
     if (test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))
         queue_work(nbd_del_wq, &nbd->remove_work);
     else
         nbd_dev_remove(nbd);
 }
 
 static int nbd_disconnected(struct nbd_config *config)
 {
     return test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags) ||
         test_bit(NBD_RT_DISCONNECT_REQUESTED, &config->runtime_flags);
 }
 
 static void nbd_mark_nsock_dead(struct nbd_device *nbd, struct nbd_sock *nsock,
                 int notify)
 {
     if (!nsock->dead && notify && !nbd_disconnected(nbd->config)) {
         struct link_dead_args *args;
         args = kmalloc(sizeof(struct link_dead_args), GFP_NOIO);
         if (args) {
             INIT_WORK(&args->work, nbd_dead_link_work);
             args->index = nbd->index;
             queue_work(system_wq, &args->work);
         }
     }
     if (!nsock->dead) {
         kernel_sock_shutdown(nsock->sock, SHUT_RDWR);
         if (atomic_dec_return(&nbd->config->live_connections) == 0) {
             if (test_and_clear_bit(NBD_RT_DISCONNECT_REQUESTED,
                            &nbd->config->runtime_flags)) {
                 set_bit(NBD_RT_DISCONNECTED,
                     &nbd->config->runtime_flags);
                 dev_info(nbd_to_dev(nbd),
                     "Disconnected due to user request.\n");
             }
         }
     }
     nsock->dead = true;
     nsock->pending = NULL;
     nsock->sent = 0;
 }
 
 static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize,
         loff_t blksize)
 {
     if (!blksize)
         blksize = 1u << NBD_DEF_BLKSIZE_BITS;
 
     if (blk_validate_block_size(blksize))
         return -EINVAL;
 
     nbd->config->bytesize = bytesize;
     nbd->config->blksize_bits = __ffs(blksize);
 
     if (!nbd->pid)
         return 0;
 
     if (nbd->config->flags & NBD_FLAG_SEND_TRIM) {
         nbd->disk->queue->limits.discard_granularity = blksize;
         blk_queue_max_discard_sectors(nbd->disk->queue, UINT_MAX);
     }
     blk_queue_logical_block_size(nbd->disk->queue, blksize);
     blk_queue_physical_block_size(nbd->disk->queue, blksize);
 
     if (max_part)
         set_bit(GD_NEED_PART_SCAN, &nbd->disk->state);
     if (!set_capacity_and_notify(nbd->disk, bytesize >> 9))
         kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
     return 0;
 }
 
 static void nbd_complete_rq(struct request *req)
 {
     struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
 
     dev_dbg(nbd_to_dev(cmd->nbd), "request %p: %s\n", req,
         cmd->status ? "failed" : "done");
 
     blk_mq_end_request(req, cmd->status);
 }
 
 /*
  * Forcibly shutdown the socket causing all listeners to error
  */
 static void sock_shutdown(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     int i;
 
     if (config->num_connections == 0)
         return;
     if (test_and_set_bit(NBD_RT_DISCONNECTED, &config->runtime_flags))
         return;
 
     for (i = 0; i < config->num_connections; i++) {
         struct nbd_sock *nsock = config->socks[i];
         mutex_lock(&nsock->tx_lock);
         nbd_mark_nsock_dead(nbd, nsock, 0);
         mutex_unlock(&nsock->tx_lock);
     }
     dev_warn(disk_to_dev(nbd->disk), "shutting down sockets\n");
 }
 
 static u32 req_to_nbd_cmd_type(struct request *req)
 {
     switch (req_op(req)) {
     case REQ_OP_DISCARD:
         return NBD_CMD_TRIM;
     case REQ_OP_FLUSH:
         return NBD_CMD_FLUSH;
     case REQ_OP_WRITE:
         return NBD_CMD_WRITE;
     case REQ_OP_READ:
         return NBD_CMD_READ;
     default:
         return U32_MAX;
     }
 }
 
 static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req)
 {
     struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
     struct nbd_device *nbd = cmd->nbd;
     struct nbd_config *config;
 
     if (!mutex_trylock(&cmd->lock))
         return BLK_EH_RESET_TIMER;
 
     if (!test_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
         mutex_unlock(&cmd->lock);
         return BLK_EH_DONE;
     }
 
     if (!refcount_inc_not_zero(&nbd->config_refs)) {
         cmd->status = BLK_STS_TIMEOUT;
         __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
         mutex_unlock(&cmd->lock);
         goto done;
     }
     config = nbd->config;
 
     if (config->num_connections > 1 ||
         (config->num_connections == 1 && nbd->tag_set.timeout)) {
         dev_err_ratelimited(nbd_to_dev(nbd),
                     "Connection timed out, retrying (%d/%d alive)\n",
                     atomic_read(&config->live_connections),
                     config->num_connections);
         /*
          * Hooray we have more connections, requeue this IO, the submit
          * path will put it on a real connection. Or if only one
          * connection is configured, the submit path will wait util
          * a new connection is reconfigured or util dead timeout.
          */
         if (config->socks) {
             if (cmd->index < config->num_connections) {
                 struct nbd_sock *nsock =
                     config->socks[cmd->index];
                 mutex_lock(&nsock->tx_lock);
                 /* We can have multiple outstanding requests, so
                  * we don't want to mark the nsock dead if we've
                  * already reconnected with a new socket, so
                  * only mark it dead if its the same socket we
                  * were sent out on.
                  */
                 if (cmd->cookie == nsock->cookie)
                     nbd_mark_nsock_dead(nbd, nsock, 1);
                 mutex_unlock(&nsock->tx_lock);
             }
             mutex_unlock(&cmd->lock);
             nbd_requeue_cmd(cmd);
             nbd_config_put(nbd);
             return BLK_EH_DONE;
         }
     }
 
     if (!nbd->tag_set.timeout) {
         /*
          * Userspace sets timeout=0 to disable socket disconnection,
          * so just warn and reset the timer.
          */
         struct nbd_sock *nsock = config->socks[cmd->index];
         cmd->retries++;
         dev_info(nbd_to_dev(nbd), "Possible stuck request %p: control (%s@%llu,%uB). Runtime %u seconds\n",
             req, nbdcmd_to_ascii(req_to_nbd_cmd_type(req)),
             (unsigned long long)blk_rq_pos(req) << 9,
             blk_rq_bytes(req), (req->timeout / HZ) * cmd->retries);
 
         mutex_lock(&nsock->tx_lock);
         if (cmd->cookie != nsock->cookie) {
             nbd_requeue_cmd(cmd);
             mutex_unlock(&nsock->tx_lock);
             mutex_unlock(&cmd->lock);
             nbd_config_put(nbd);
             return BLK_EH_DONE;
         }
         mutex_unlock(&nsock->tx_lock);
         mutex_unlock(&cmd->lock);
         nbd_config_put(nbd);
         return BLK_EH_RESET_TIMER;
     }
 
     dev_err_ratelimited(nbd_to_dev(nbd), "Connection timed out\n");
     set_bit(NBD_RT_TIMEDOUT, &config->runtime_flags);
     cmd->status = BLK_STS_IOERR;
     __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
     mutex_unlock(&cmd->lock);
     sock_shutdown(nbd);
     nbd_config_put(nbd);
 done:
     blk_mq_complete_request(req);
     return BLK_EH_DONE;
 }
 
 /*
  *  Send or receive packet. Return a positive value on success and
  *  negtive value on failue, and never return 0.
  */
 static int sock_xmit(struct nbd_device *nbd, int index, int send,
              struct iov_iter *iter, int msg_flags, int *sent)
 {
     struct nbd_config *config = nbd->config;
     struct socket *sock = config->socks[index]->sock;
     int result;
     struct msghdr msg;
     unsigned int noreclaim_flag;
 
     if (unlikely(!sock)) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
             "Attempted %s on closed socket in sock_xmit\n",
             (send ? "send" : "recv"));
         return -EINVAL;
     }
 
     msg.msg_iter = *iter;
 
     noreclaim_flag = memalloc_noreclaim_save();
     do {
         sock->sk->sk_allocation = GFP_NOIO | __GFP_MEMALLOC;
         msg.msg_name = NULL;
         msg.msg_namelen = 0;
         msg.msg_control = NULL;
         msg.msg_controllen = 0;
         msg.msg_flags = msg_flags | MSG_NOSIGNAL;
 
         if (send)
             result = sock_sendmsg(sock, &msg);
         else
             result = sock_recvmsg(sock, &msg, msg.msg_flags);
 
         if (result <= 0) {
             if (result == 0)
                 result = -EPIPE; /* short read */
             break;
         }
         if (sent)
             *sent += result;
     } while (msg_data_left(&msg));
 
     memalloc_noreclaim_restore(noreclaim_flag);
 
     return result;
 }
 
 /*
  * Different settings for sk->sk_sndtimeo can result in different return values
  * if there is a signal pending when we enter sendmsg, because reasons?
  */
 static inline int was_interrupted(int result)
 {
     return result == -ERESTARTSYS || result == -EINTR;
 }
 
 /* always call with the tx_lock held */
 static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
 {
     struct request *req = blk_mq_rq_from_pdu(cmd);
     struct nbd_config *config = nbd->config;
     struct nbd_sock *nsock = config->socks[index];
     int result;
     struct nbd_request request = {.magic = htonl(NBD_REQUEST_MAGIC)};
     struct kvec iov = {.iov_base = &request, .iov_len = sizeof(request)};
     struct iov_iter from;
     unsigned long size = blk_rq_bytes(req);
     struct bio *bio;
     u64 handle;
     u32 type;
     u32 nbd_cmd_flags = 0;
     int sent = nsock->sent, skip = 0;
 
     iov_iter_kvec(&from, WRITE, &iov, 1, sizeof(request));
 
     type = req_to_nbd_cmd_type(req);
     if (type == U32_MAX)
         return -EIO;
 
     if (rq_data_dir(req) == WRITE &&
         (config->flags & NBD_FLAG_READ_ONLY)) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
                     "Write on read-only\n");
         return -EIO;
     }
 
     if (req->cmd_flags & REQ_FUA)
         nbd_cmd_flags |= NBD_CMD_FLAG_FUA;
 
     /* We did a partial send previously, and we at least sent the whole
      * request struct, so just go and send the rest of the pages in the
      * request.
      */
     if (sent) {
         if (sent >= sizeof(request)) {
             skip = sent - sizeof(request);
 
             /* initialize handle for tracing purposes */
             handle = nbd_cmd_handle(cmd);
 
             goto send_pages;
         }
         iov_iter_advance(&from, sent);
     } else {
         cmd->cmd_cookie++;
     }
     cmd->index = index;
     cmd->cookie = nsock->cookie;
     cmd->retries = 0;
     request.type = htonl(type | nbd_cmd_flags);
     if (type != NBD_CMD_FLUSH) {
         request.from = cpu_to_be64((u64)blk_rq_pos(req) << 9);
         request.len = htonl(size);
     }
     handle = nbd_cmd_handle(cmd);
     memcpy(request.handle, &handle, sizeof(handle));
 
     trace_nbd_send_request(&request, nbd->index, blk_mq_rq_from_pdu(cmd));
 
     dev_dbg(nbd_to_dev(nbd), "request %p: sending control (%s@%llu,%uB)\n",
         req, nbdcmd_to_ascii(type),
         (unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
     result = sock_xmit(nbd, index, 1, &from,
             (type == NBD_CMD_WRITE) ? MSG_MORE : 0, &sent);
     trace_nbd_header_sent(req, handle);
     if (result < 0) {
         if (was_interrupted(result)) {
             /* If we havne't sent anything we can just return BUSY,
              * however if we have sent something we need to make
              * sure we only allow this req to be sent until we are
              * completely done.
              */
             if (sent) {
                 nsock->pending = req;
                 nsock->sent = sent;
             }
             set_bit(NBD_CMD_REQUEUED, &cmd->flags);
             return BLK_STS_RESOURCE;
         }
         dev_err_ratelimited(disk_to_dev(nbd->disk),
             "Send control failed (result %d)\n", result);
         return -EAGAIN;
     }
 send_pages:
     if (type != NBD_CMD_WRITE)
         goto out;
 
     bio = req->bio;
     while (bio) {
         struct bio *next = bio->bi_next;
         struct bvec_iter iter;
         struct bio_vec bvec;
 
         bio_for_each_segment(bvec, bio, iter) {
             bool is_last = !next && bio_iter_last(bvec, iter);
             int flags = is_last ? 0 : MSG_MORE;
 
             dev_dbg(nbd_to_dev(nbd), "request %p: sending %d bytes data\n",
                 req, bvec.bv_len);
             iov_iter_bvec(&from, WRITE, &bvec, 1, bvec.bv_len);
             if (skip) {
                 if (skip >= iov_iter_count(&from)) {
                     skip -= iov_iter_count(&from);
                     continue;
                 }
                 iov_iter_advance(&from, skip);
                 skip = 0;
             }
             result = sock_xmit(nbd, index, 1, &from, flags, &sent);
             if (result < 0) {
                 if (was_interrupted(result)) {
                     /* We've already sent the header, we
                      * have no choice but to set pending and
                      * return BUSY.
                      */
                     nsock->pending = req;
                     nsock->sent = sent;
                     set_bit(NBD_CMD_REQUEUED, &cmd->flags);
                     return BLK_STS_RESOURCE;
                 }
                 dev_err(disk_to_dev(nbd->disk),
                     "Send data failed (result %d)\n",
                     result);
                 return -EAGAIN;
             }
             /*
              * The completion might already have come in,
              * so break for the last one instead of letting
              * the iterator do it. This prevents use-after-free
              * of the bio.
              */
             if (is_last)
                 break;
         }
         bio = next;
     }
 out:
     trace_nbd_payload_sent(req, handle);
     nsock->pending = NULL;
     nsock->sent = 0;
     return 0;
 }
 
 static int nbd_read_reply(struct nbd_device *nbd, int index,
               struct nbd_reply *reply)
 {
     struct kvec iov = {.iov_base = reply, .iov_len = sizeof(*reply)};
     struct iov_iter to;
     int result;
 
     reply->magic = 0;
     iov_iter_kvec(&to, READ, &iov, 1, sizeof(*reply));
     result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
     if (result < 0) {
         if (!nbd_disconnected(nbd->config))
             dev_err(disk_to_dev(nbd->disk),
                 "Receive control failed (result %d)\n", result);
         return result;
     }
 
     if (ntohl(reply->magic) != NBD_REPLY_MAGIC) {
         dev_err(disk_to_dev(nbd->disk), "Wrong magic (0x%lx)\n",
                 (unsigned long)ntohl(reply->magic));
         return -EPROTO;
     }
 
     return 0;
 }
 
 /* NULL returned = something went wrong, inform userspace */
 static struct nbd_cmd *nbd_handle_reply(struct nbd_device *nbd, int index,
                     struct nbd_reply *reply)
 {
     int result;
     struct nbd_cmd *cmd;
     struct request *req = NULL;
     u64 handle;
     u16 hwq;
     u32 tag;
     int ret = 0;
 
     memcpy(&handle, reply->handle, sizeof(handle));
     tag = nbd_handle_to_tag(handle);
     hwq = blk_mq_unique_tag_to_hwq(tag);
     if (hwq < nbd->tag_set.nr_hw_queues)
         req = blk_mq_tag_to_rq(nbd->tag_set.tags[hwq],
                        blk_mq_unique_tag_to_tag(tag));
     if (!req || !blk_mq_request_started(req)) {
         dev_err(disk_to_dev(nbd->disk), "Unexpected reply (%d) %p\n",
             tag, req);
         return ERR_PTR(-ENOENT);
     }
     trace_nbd_header_received(req, handle);
     cmd = blk_mq_rq_to_pdu(req);
 
     mutex_lock(&cmd->lock);
     if (!test_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
         dev_err(disk_to_dev(nbd->disk), "Suspicious reply %d (status %u flags %lu)",
             tag, cmd->status, cmd->flags);
         ret = -ENOENT;
         goto out;
     }
     if (cmd->index != index) {
         dev_err(disk_to_dev(nbd->disk), "Unexpected reply %d from different sock %d (expected %d)",
             tag, index, cmd->index);
         ret = -ENOENT;
         goto out;
     }
     if (cmd->cmd_cookie != nbd_handle_to_cookie(handle)) {
         dev_err(disk_to_dev(nbd->disk), "Double reply on req %p, cmd_cookie %u, handle cookie %u\n",
             req, cmd->cmd_cookie, nbd_handle_to_cookie(handle));
         ret = -ENOENT;
         goto out;
     }
     if (cmd->status != BLK_STS_OK) {
         dev_err(disk_to_dev(nbd->disk), "Command already handled %p\n",
             req);
         ret = -ENOENT;
         goto out;
     }
     if (test_bit(NBD_CMD_REQUEUED, &cmd->flags)) {
         dev_err(disk_to_dev(nbd->disk), "Raced with timeout on req %p\n",
             req);
         ret = -ENOENT;
         goto out;
     }
     if (ntohl(reply->error)) {
         dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
             ntohl(reply->error));
         cmd->status = BLK_STS_IOERR;
         goto out;
     }
 
     dev_dbg(nbd_to_dev(nbd), "request %p: got reply\n", req);
     if (rq_data_dir(req) != WRITE) {
         struct req_iterator iter;
         struct bio_vec bvec;
         struct iov_iter to;
 
         rq_for_each_segment(bvec, req, iter) {
             iov_iter_bvec(&to, READ, &bvec, 1, bvec.bv_len);
             result = sock_xmit(nbd, index, 0, &to, MSG_WAITALL, NULL);
             if (result < 0) {
                 dev_err(disk_to_dev(nbd->disk), "Receive data failed (result %d)\n",
                     result);
                 /*
                  * If we've disconnected, we need to make sure we
                  * complete this request, otherwise error out
                  * and let the timeout stuff handle resubmitting
                  * this request onto another connection.
                  */
                 if (nbd_disconnected(nbd->config)) {
                     cmd->status = BLK_STS_IOERR;
                     goto out;
                 }
                 ret = -EIO;
                 goto out;
             }
             dev_dbg(nbd_to_dev(nbd), "request %p: got %d bytes data\n",
                 req, bvec.bv_len);
         }
     }
 out:
     trace_nbd_payload_received(req, handle);
     mutex_unlock(&cmd->lock);
     return ret ? ERR_PTR(ret) : cmd;
 }
 
 static void recv_work(struct work_struct *work)
 {
     struct recv_thread_args *args = container_of(work,
                              struct recv_thread_args,
                              work);
     struct nbd_device *nbd = args->nbd;
     struct nbd_config *config = nbd->config;
     struct request_queue *q = nbd->disk->queue;
     struct nbd_sock *nsock;
     struct nbd_cmd *cmd;
     struct request *rq;
 
     while (1) {
         struct nbd_reply reply;
 
         if (nbd_read_reply(nbd, args->index, &reply))
             break;
 
         /*
          * Grab .q_usage_counter so request pool won't go away, then no
          * request use-after-free is possible during nbd_handle_reply().
          * If queue is frozen, there won't be any inflight requests, we
          * needn't to handle the incoming garbage message.
          */
         if (!percpu_ref_tryget(&q->q_usage_counter)) {
             dev_err(disk_to_dev(nbd->disk), "%s: no io inflight\n",
                 __func__);
             break;
         }
 
         cmd = nbd_handle_reply(nbd, args->index, &reply);
         if (IS_ERR(cmd)) {
             percpu_ref_put(&q->q_usage_counter);
             break;
         }
 
         rq = blk_mq_rq_from_pdu(cmd);
         if (likely(!blk_should_fake_timeout(rq->q))) {
             bool complete;
 
             mutex_lock(&cmd->lock);
             complete = __test_and_clear_bit(NBD_CMD_INFLIGHT,
                             &cmd->flags);
             mutex_unlock(&cmd->lock);
             if (complete)
                 blk_mq_complete_request(rq);
         }
         percpu_ref_put(&q->q_usage_counter);
     }
 
     nsock = config->socks[args->index];
     mutex_lock(&nsock->tx_lock);
     nbd_mark_nsock_dead(nbd, nsock, 1);
     mutex_unlock(&nsock->tx_lock);
 
     nbd_config_put(nbd);
     atomic_dec(&config->recv_threads);
     wake_up(&config->recv_wq);
     kfree(args);
 }
 
 static bool nbd_clear_req(struct request *req, void *data)
 {
     struct nbd_cmd *cmd = blk_mq_rq_to_pdu(req);
 
     /* don't abort one completed request */
     if (blk_mq_request_completed(req))
         return true;
 
     mutex_lock(&cmd->lock);
     if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
         mutex_unlock(&cmd->lock);
         return true;
     }
     cmd->status = BLK_STS_IOERR;
     mutex_unlock(&cmd->lock);
 
     blk_mq_complete_request(req);
     return true;
 }
 
 static void nbd_clear_que(struct nbd_device *nbd)
 {
     blk_mq_quiesce_queue(nbd->disk->queue);
     blk_mq_tagset_busy_iter(&nbd->tag_set, nbd_clear_req, NULL);
     blk_mq_unquiesce_queue(nbd->disk->queue);
     dev_dbg(disk_to_dev(nbd->disk), "queue cleared\n");
 }
 
 static int find_fallback(struct nbd_device *nbd, int index)
 {
     struct nbd_config *config = nbd->config;
     int new_index = -1;
     struct nbd_sock *nsock = config->socks[index];
     int fallback = nsock->fallback_index;
 
     if (test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags))
         return new_index;
 
     if (config->num_connections <= 1) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
                     "Dead connection, failed to find a fallback\n");
         return new_index;
     }
 
     if (fallback >= 0 && fallback < config->num_connections &&
         !config->socks[fallback]->dead)
         return fallback;
 
     if (nsock->fallback_index < 0 ||
         nsock->fallback_index >= config->num_connections ||
         config->socks[nsock->fallback_index]->dead) {
         int i;
         for (i = 0; i < config->num_connections; i++) {
             if (i == index)
                 continue;
             if (!config->socks[i]->dead) {
                 new_index = i;
                 break;
             }
         }
         nsock->fallback_index = new_index;
         if (new_index < 0) {
             dev_err_ratelimited(disk_to_dev(nbd->disk),
                         "Dead connection, failed to find a fallback\n");
             return new_index;
         }
     }
     new_index = nsock->fallback_index;
     return new_index;
 }
 
 static int wait_for_reconnect(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     if (!config->dead_conn_timeout)
         return 0;
 
     if (!wait_event_timeout(config->conn_wait,
                 test_bit(NBD_RT_DISCONNECTED,
                      &config->runtime_flags) ||
                 atomic_read(&config->live_connections) > 0,
                 config->dead_conn_timeout))
         return 0;
 
     return !test_bit(NBD_RT_DISCONNECTED, &config->runtime_flags);
 }
 
 static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
 {
     struct request *req = blk_mq_rq_from_pdu(cmd);
     struct nbd_device *nbd = cmd->nbd;
     struct nbd_config *config;
     struct nbd_sock *nsock;
     int ret;
 
     if (!refcount_inc_not_zero(&nbd->config_refs)) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
                     "Socks array is empty\n");
         return -EINVAL;
     }
     config = nbd->config;
 
     if (index >= config->num_connections) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
                     "Attempted send on invalid socket\n");
         nbd_config_put(nbd);
         return -EINVAL;
     }
     cmd->status = BLK_STS_OK;
 again:
     nsock = config->socks[index];
     mutex_lock(&nsock->tx_lock);
     if (nsock->dead) {
         int old_index = index;
         index = find_fallback(nbd, index);
         mutex_unlock(&nsock->tx_lock);
         if (index < 0) {
             if (wait_for_reconnect(nbd)) {
                 index = old_index;
                 goto again;
             }
             /* All the sockets should already be down at this point,
              * we just want to make sure that DISCONNECTED is set so
              * any requests that come in that were queue'ed waiting
              * for the reconnect timer don't trigger the timer again
              * and instead just error out.
              */
             sock_shutdown(nbd);
             nbd_config_put(nbd);
             return -EIO;
         }
         goto again;
     }
 
     /* Handle the case that we have a pending request that was partially
      * transmitted that _has_ to be serviced first.  We need to call requeue
      * here so that it gets put _after_ the request that is already on the
      * dispatch list.
      */
     blk_mq_start_request(req);
     if (unlikely(nsock->pending && nsock->pending != req)) {
         nbd_requeue_cmd(cmd);
         ret = 0;
         goto out;
     }
     /*
      * Some failures are related to the link going down, so anything that
      * returns EAGAIN can be retried on a different socket.
      */
     ret = nbd_send_cmd(nbd, cmd, index);
     /*
      * Access to this flag is protected by cmd->lock, thus it's safe to set
      * the flag after nbd_send_cmd() succeed to send request to server.
      */
     if (!ret)
         __set_bit(NBD_CMD_INFLIGHT, &cmd->flags);
     else if (ret == -EAGAIN) {
         dev_err_ratelimited(disk_to_dev(nbd->disk),
                     "Request send failed, requeueing\n");
         nbd_mark_nsock_dead(nbd, nsock, 1);
         nbd_requeue_cmd(cmd);
         ret = 0;
     }
 out:
     mutex_unlock(&nsock->tx_lock);
     nbd_config_put(nbd);
     return ret;
 }
 
 static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
             const struct blk_mq_queue_data *bd)
 {
     struct nbd_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
     int ret;
 
     /*
      * Since we look at the bio's to send the request over the network we
      * need to make sure the completion work doesn't mark this request done
      * before we are done doing our send.  This keeps us from dereferencing
      * freed data if we have particularly fast completions (ie we get the
      * completion before we exit sock_xmit on the last bvec) or in the case
      * that the server is misbehaving (or there was an error) before we're
      * done sending everything over the wire.
      */
     mutex_lock(&cmd->lock);
     clear_bit(NBD_CMD_REQUEUED, &cmd->flags);
 
     /* We can be called directly from the user space process, which means we
      * could possibly have signals pending so our sendmsg will fail.  In
      * this case we need to return that we are busy, otherwise error out as
      * appropriate.
      */
     ret = nbd_handle_cmd(cmd, hctx->queue_num);
     if (ret < 0)
         ret = BLK_STS_IOERR;
     else if (!ret)
         ret = BLK_STS_OK;
     mutex_unlock(&cmd->lock);
 
     return ret;
 }
 
 static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
                      int *err)
 {
     struct socket *sock;
 
     *err = 0;
     sock = sockfd_lookup(fd, err);
     if (!sock)
         return NULL;
 
     if (sock->ops->shutdown == sock_no_shutdown) {
         dev_err(disk_to_dev(nbd->disk), "Unsupported socket: shutdown callout must be supported.\n");
         *err = -EINVAL;
         sockfd_put(sock);
         return NULL;
     }
 
     return sock;
 }
 
 static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
               bool netlink)
 {
     struct nbd_config *config = nbd->config;
     struct socket *sock;
     struct nbd_sock **socks;
     struct nbd_sock *nsock;
     int err;
 
     sock = nbd_get_socket(nbd, arg, &err);
     if (!sock)
         return err;
 
     /*
      * We need to make sure we don't get any errant requests while we're
      * reallocating the ->socks array.
      */
     blk_mq_freeze_queue(nbd->disk->queue);
 
     if (!netlink && !nbd->task_setup &&
         !test_bit(NBD_RT_BOUND, &config->runtime_flags))
         nbd->task_setup = current;
 
     if (!netlink &&
         (nbd->task_setup != current ||
          test_bit(NBD_RT_BOUND, &config->runtime_flags))) {
         dev_err(disk_to_dev(nbd->disk),
             "Device being setup by another task");
         err = -EBUSY;
         goto put_socket;
     }
 
     nsock = kzalloc(sizeof(*nsock), GFP_KERNEL);
     if (!nsock) {
         err = -ENOMEM;
         goto put_socket;
     }
 
     socks = krealloc(config->socks, (config->num_connections + 1) *
              sizeof(struct nbd_sock *), GFP_KERNEL);
     if (!socks) {
         kfree(nsock);
         err = -ENOMEM;
         goto put_socket;
     }
 
     config->socks = socks;
 
     nsock->fallback_index = -1;
     nsock->dead = false;
     mutex_init(&nsock->tx_lock);
     nsock->sock = sock;
     nsock->pending = NULL;
     nsock->sent = 0;
     nsock->cookie = 0;
     socks[config->num_connections++] = nsock;
     atomic_inc(&config->live_connections);
     blk_mq_unfreeze_queue(nbd->disk->queue);
 
     return 0;
 
 put_socket:
     blk_mq_unfreeze_queue(nbd->disk->queue);
     sockfd_put(sock);
     return err;
 }
 
 static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
 {
     struct nbd_config *config = nbd->config;
     struct socket *sock, *old;
     struct recv_thread_args *args;
     int i;
     int err;
 
     sock = nbd_get_socket(nbd, arg, &err);
     if (!sock)
         return err;
 
     args = kzalloc(sizeof(*args), GFP_KERNEL);
     if (!args) {
         sockfd_put(sock);
         return -ENOMEM;
     }
 
     for (i = 0; i < config->num_connections; i++) {
         struct nbd_sock *nsock = config->socks[i];
 
         if (!nsock->dead)
             continue;
 
         mutex_lock(&nsock->tx_lock);
         if (!nsock->dead) {
             mutex_unlock(&nsock->tx_lock);
             continue;
         }
         sk_set_memalloc(sock->sk);
         if (nbd->tag_set.timeout)
             sock->sk->sk_sndtimeo = nbd->tag_set.timeout;
         atomic_inc(&config->recv_threads);
         refcount_inc(&nbd->config_refs);
         old = nsock->sock;
         nsock->fallback_index = -1;
         nsock->sock = sock;
         nsock->dead = false;
         INIT_WORK(&args->work, recv_work);
         args->index = i;
         args->nbd = nbd;
         nsock->cookie++;
         mutex_unlock(&nsock->tx_lock);
         sockfd_put(old);
 
         clear_bit(NBD_RT_DISCONNECTED, &config->runtime_flags);
 
         /* We take the tx_mutex in an error path in the recv_work, so we
          * need to queue_work outside of the tx_mutex.
          */
         queue_work(nbd->recv_workq, &args->work);
 
         atomic_inc(&config->live_connections);
         wake_up(&config->conn_wait);
         return 0;
     }
     sockfd_put(sock);
     kfree(args);
     return -ENOSPC;
 }
 
 static void nbd_bdev_reset(struct nbd_device *nbd)
 {
     if (disk_openers(nbd->disk) > 1)
         return;
     set_capacity(nbd->disk, 0);
 }
 
 static void nbd_parse_flags(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     if (config->flags & NBD_FLAG_READ_ONLY)
         set_disk_ro(nbd->disk, true);
     else
         set_disk_ro(nbd->disk, false);
     if (config->flags & NBD_FLAG_SEND_FLUSH) {
         if (config->flags & NBD_FLAG_SEND_FUA)
             blk_queue_write_cache(nbd->disk->queue, true, true);
         else
             blk_queue_write_cache(nbd->disk->queue, true, false);
     }
     else
         blk_queue_write_cache(nbd->disk->queue, false, false);
 }
 
 static void send_disconnects(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     struct nbd_request request = {
         .magic = htonl(NBD_REQUEST_MAGIC),
         .type = htonl(NBD_CMD_DISC),
     };
     struct kvec iov = {.iov_base = &request, .iov_len = sizeof(request)};
     struct iov_iter from;
     int i, ret;
 
     for (i = 0; i < config->num_connections; i++) {
         struct nbd_sock *nsock = config->socks[i];
 
         iov_iter_kvec(&from, WRITE, &iov, 1, sizeof(request));
         mutex_lock(&nsock->tx_lock);
         ret = sock_xmit(nbd, i, 1, &from, 0, NULL);
         if (ret < 0)
             dev_err(disk_to_dev(nbd->disk),
                 "Send disconnect failed %d\n", ret);
         mutex_unlock(&nsock->tx_lock);
     }
 }
 
 static int nbd_disconnect(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
 
     dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n");
     set_bit(NBD_RT_DISCONNECT_REQUESTED, &config->runtime_flags);
     set_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags);
     send_disconnects(nbd);
     return 0;
 }
 
 static void nbd_clear_sock(struct nbd_device *nbd)
 {
     sock_shutdown(nbd);
     nbd_clear_que(nbd);
     nbd->task_setup = NULL;
 }
 
 static void nbd_config_put(struct nbd_device *nbd)
 {
     if (refcount_dec_and_mutex_lock(&nbd->config_refs,
                     &nbd->config_lock)) {
         struct nbd_config *config = nbd->config;
         nbd_dev_dbg_close(nbd);
         invalidate_disk(nbd->disk);
         if (nbd->config->bytesize)
             kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
         if (test_and_clear_bit(NBD_RT_HAS_PID_FILE,
                        &config->runtime_flags))
             device_remove_file(disk_to_dev(nbd->disk), &pid_attr);
         nbd->pid = 0;
         if (test_and_clear_bit(NBD_RT_HAS_BACKEND_FILE,
                        &config->runtime_flags)) {
             device_remove_file(disk_to_dev(nbd->disk), &backend_attr);
             kfree(nbd->backend);
             nbd->backend = NULL;
         }
         nbd_clear_sock(nbd);
         if (config->num_connections) {
             int i;
             for (i = 0; i < config->num_connections; i++) {
                 sockfd_put(config->socks[i]->sock);
                 kfree(config->socks[i]);
             }
             kfree(config->socks);
         }
         kfree(nbd->config);
         nbd->config = NULL;
 
         nbd->tag_set.timeout = 0;
         nbd->disk->queue->limits.discard_granularity = 0;
         blk_queue_max_discard_sectors(nbd->disk->queue, 0);
 
         mutex_unlock(&nbd->config_lock);
         nbd_put(nbd);
         module_put(THIS_MODULE);
     }
 }
 
 static int nbd_start_device(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     int num_connections = config->num_connections;
     int error = 0, i;
 
     if (nbd->pid)
         return -EBUSY;
     if (!config->socks)
         return -EINVAL;
     if (num_connections > 1 &&
         !(config->flags & NBD_FLAG_CAN_MULTI_CONN)) {
         dev_err(disk_to_dev(nbd->disk), "server does not support multiple connections per device.\n");
         return -EINVAL;
     }
 
     blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections);
     nbd->pid = task_pid_nr(current);
 
     nbd_parse_flags(nbd);
 
     error = device_create_file(disk_to_dev(nbd->disk), &pid_attr);
     if (error) {
         dev_err(disk_to_dev(nbd->disk), "device_create_file failed for pid!\n");
         return error;
     }
     set_bit(NBD_RT_HAS_PID_FILE, &config->runtime_flags);
 
     nbd_dev_dbg_init(nbd);
     for (i = 0; i < num_connections; i++) {
         struct recv_thread_args *args;
 
         args = kzalloc(sizeof(*args), GFP_KERNEL);
         if (!args) {
             sock_shutdown(nbd);
             /*
              * If num_connections is m (2 < m),
              * and NO.1 ~ NO.n(1 < n < m) kzallocs are successful.
              * But NO.(n + 1) failed. We still have n recv threads.
              * So, add flush_workqueue here to prevent recv threads
              * dropping the last config_refs and trying to destroy
              * the workqueue from inside the workqueue.
              */
             if (i)
                 flush_workqueue(nbd->recv_workq);
             return -ENOMEM;
         }
         sk_set_memalloc(config->socks[i]->sock->sk);
         if (nbd->tag_set.timeout)
             config->socks[i]->sock->sk->sk_sndtimeo =
                 nbd->tag_set.timeout;
         atomic_inc(&config->recv_threads);
         refcount_inc(&nbd->config_refs);
         INIT_WORK(&args->work, recv_work);
         args->nbd = nbd;
         args->index = i;
         queue_work(nbd->recv_workq, &args->work);
     }
     return nbd_set_size(nbd, config->bytesize, nbd_blksize(config));
 }
 
 static int nbd_start_device_ioctl(struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     int ret;
 
     ret = nbd_start_device(nbd);
     if (ret)
         return ret;
 
     if (max_part)
         set_bit(GD_NEED_PART_SCAN, &nbd->disk->state);
     mutex_unlock(&nbd->config_lock);
     ret = wait_event_interruptible(config->recv_wq,
                      atomic_read(&config->recv_threads) == 0);
     if (ret)
         sock_shutdown(nbd);
     flush_workqueue(nbd->recv_workq);
 
     mutex_lock(&nbd->config_lock);
     nbd_bdev_reset(nbd);
     /* user requested, ignore socket errors */
     if (test_bit(NBD_RT_DISCONNECT_REQUESTED, &config->runtime_flags))
         ret = 0;
     if (test_bit(NBD_RT_TIMEDOUT, &config->runtime_flags))
         ret = -ETIMEDOUT;
     return ret;
 }
 
 static void nbd_clear_sock_ioctl(struct nbd_device *nbd,
                  struct block_device *bdev)
 {
     nbd_clear_sock(nbd);
     __invalidate_device(bdev, true);
     nbd_bdev_reset(nbd);
     if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF,
                    &nbd->config->runtime_flags))
         nbd_config_put(nbd);
 }
 
 static void nbd_set_cmd_timeout(struct nbd_device *nbd, u64 timeout)
 {
     nbd->tag_set.timeout = timeout * HZ;
     if (timeout)
         blk_queue_rq_timeout(nbd->disk->queue, timeout * HZ);
     else
         blk_queue_rq_timeout(nbd->disk->queue, 30 * HZ);
 }
 
 /* Must be called with config_lock held */
 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
                unsigned int cmd, unsigned long arg)
 {
     struct nbd_config *config = nbd->config;
     loff_t bytesize;
 
     switch (cmd) {
     case NBD_DISCONNECT:
         return nbd_disconnect(nbd);
     case NBD_CLEAR_SOCK:
         nbd_clear_sock_ioctl(nbd, bdev);
         return 0;
     case NBD_SET_SOCK:
         return nbd_add_socket(nbd, arg, false);
     case NBD_SET_BLKSIZE:
         return nbd_set_size(nbd, config->bytesize, arg);
     case NBD_SET_SIZE:
         return nbd_set_size(nbd, arg, nbd_blksize(config));
     case NBD_SET_SIZE_BLOCKS:
         if (check_shl_overflow(arg, config->blksize_bits, &bytesize))
             return -EINVAL;
         return nbd_set_size(nbd, bytesize, nbd_blksize(config));
     case NBD_SET_TIMEOUT:
         nbd_set_cmd_timeout(nbd, arg);
         return 0;
 
     case NBD_SET_FLAGS:
         config->flags = arg;
         return 0;
     case NBD_DO_IT:
         return nbd_start_device_ioctl(nbd);
     case NBD_CLEAR_QUE:
         /*
          * This is for compatibility only.  The queue is always cleared
          * by NBD_DO_IT or NBD_CLEAR_SOCK.
          */
         return 0;
     case NBD_PRINT_DEBUG:
         /*
          * For compatibility only, we no longer keep a list of
          * outstanding requests.
          */
         return 0;
     }
     return -ENOTTY;
 }
 
 static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
              unsigned int cmd, unsigned long arg)
 {
     struct nbd_device *nbd = bdev->bd_disk->private_data;
     struct nbd_config *config = nbd->config;
     int error = -EINVAL;
 
     if (!capable(CAP_SYS_ADMIN))
         return -EPERM;
 
     /* The block layer will pass back some non-nbd ioctls in case we have
      * special handling for them, but we don't so just return an error.
      */
     if (_IOC_TYPE(cmd) != 0xab)
         return -EINVAL;
 
     mutex_lock(&nbd->config_lock);
 
     /* Don't allow ioctl operations on a nbd device that was created with
      * netlink, unless it's DISCONNECT or CLEAR_SOCK, which are fine.
      */
     if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) ||
         (cmd == NBD_DISCONNECT || cmd == NBD_CLEAR_SOCK))
         error = __nbd_ioctl(bdev, nbd, cmd, arg);
     else
         dev_err(nbd_to_dev(nbd), "Cannot use ioctl interface on a netlink controlled device.\n");
     mutex_unlock(&nbd->config_lock);
     return error;
 }
 
 static struct nbd_config *nbd_alloc_config(void)
 {
     struct nbd_config *config;
 
     if (!try_module_get(THIS_MODULE))
         return ERR_PTR(-ENODEV);
 
     config = kzalloc(sizeof(struct nbd_config), GFP_NOFS);
     if (!config) {
         module_put(THIS_MODULE);
         return ERR_PTR(-ENOMEM);
     }
 
     atomic_set(&config->recv_threads, 0);
     init_waitqueue_head(&config->recv_wq);
     init_waitqueue_head(&config->conn_wait);
     config->blksize_bits = NBD_DEF_BLKSIZE_BITS;
     atomic_set(&config->live_connections, 0);
     return config;
 }
 
 static int nbd_open(struct block_device *bdev, fmode_t mode)
 {
     struct nbd_device *nbd;
     int ret = 0;
 
     mutex_lock(&nbd_index_mutex);
     nbd = bdev->bd_disk->private_data;
     if (!nbd) {
         ret = -ENXIO;
         goto out;
     }
     if (!refcount_inc_not_zero(&nbd->refs)) {
         ret = -ENXIO;
         goto out;
     }
     if (!refcount_inc_not_zero(&nbd->config_refs)) {
         struct nbd_config *config;
 
         mutex_lock(&nbd->config_lock);
         if (refcount_inc_not_zero(&nbd->config_refs)) {
             mutex_unlock(&nbd->config_lock);
             goto out;
         }
         config = nbd_alloc_config();
         if (IS_ERR(config)) {
             ret = PTR_ERR(config);
             mutex_unlock(&nbd->config_lock);
             goto out;
         }
         nbd->config = config;
         refcount_set(&nbd->config_refs, 1);
         refcount_inc(&nbd->refs);
         mutex_unlock(&nbd->config_lock);
         if (max_part)
             set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
     } else if (nbd_disconnected(nbd->config)) {
         if (max_part)
             set_bit(GD_NEED_PART_SCAN, &bdev->bd_disk->state);
     }
 out:
     mutex_unlock(&nbd_index_mutex);
     return ret;
 }
 
 static void nbd_release(struct gendisk *disk, fmode_t mode)
 {
     struct nbd_device *nbd = disk->private_data;
 
     if (test_bit(NBD_RT_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
             disk_openers(disk) == 0)
         nbd_disconnect_and_put(nbd);
 
     nbd_config_put(nbd);
     nbd_put(nbd);
 }
 
 static const struct block_device_operations nbd_fops =
 {
     .owner =    THIS_MODULE,
     .open =     nbd_open,
     .release =  nbd_release,
     .ioctl =    nbd_ioctl,
     .compat_ioctl = nbd_ioctl,
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 
 static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
 {
     struct nbd_device *nbd = s->private;
 
     if (nbd->pid)
         seq_printf(s, "recv: %d\n", nbd->pid);
 
     return 0;
 }
 
 DEFINE_SHOW_ATTRIBUTE(nbd_dbg_tasks);
 
 static int nbd_dbg_flags_show(struct seq_file *s, void *unused)
 {
     struct nbd_device *nbd = s->private;
     u32 flags = nbd->config->flags;
 
     seq_printf(s, "Hex: 0x%08x\n\n", flags);
 
     seq_puts(s, "Known flags:\n");
 
     if (flags & NBD_FLAG_HAS_FLAGS)
         seq_puts(s, "NBD_FLAG_HAS_FLAGS\n");
     if (flags & NBD_FLAG_READ_ONLY)
         seq_puts(s, "NBD_FLAG_READ_ONLY\n");
     if (flags & NBD_FLAG_SEND_FLUSH)
         seq_puts(s, "NBD_FLAG_SEND_FLUSH\n");
     if (flags & NBD_FLAG_SEND_FUA)
         seq_puts(s, "NBD_FLAG_SEND_FUA\n");
     if (flags & NBD_FLAG_SEND_TRIM)
         seq_puts(s, "NBD_FLAG_SEND_TRIM\n");
 
     return 0;
 }
 
 DEFINE_SHOW_ATTRIBUTE(nbd_dbg_flags);
 
 static int nbd_dev_dbg_init(struct nbd_device *nbd)
 {
     struct dentry *dir;
     struct nbd_config *config = nbd->config;
 
     if (!nbd_dbg_dir)
         return -EIO;
 
     dir = debugfs_create_dir(nbd_name(nbd), nbd_dbg_dir);
     if (!dir) {
         dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s'\n",
             nbd_name(nbd));
         return -EIO;
     }
     config->dbg_dir = dir;
 
     debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_fops);
     debugfs_create_u64("size_bytes", 0444, dir, &config->bytesize);
     debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout);
     debugfs_create_u32("blocksize_bits", 0444, dir, &config->blksize_bits);
     debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_fops);
 
     return 0;
 }
 
 static void nbd_dev_dbg_close(struct nbd_device *nbd)
 {
     debugfs_remove_recursive(nbd->config->dbg_dir);
 }
 
 static int nbd_dbg_init(void)
 {
     struct dentry *dbg_dir;
 
     dbg_dir = debugfs_create_dir("nbd", NULL);
     if (!dbg_dir)
         return -EIO;
 
     nbd_dbg_dir = dbg_dir;
 
     return 0;
 }
 
 static void nbd_dbg_close(void)
 {
     debugfs_remove_recursive(nbd_dbg_dir);
 }
 
 #else  /* IS_ENABLED(CONFIG_DEBUG_FS) */
 
 static int nbd_dev_dbg_init(struct nbd_device *nbd)
 {
     return 0;
 }
 
 static void nbd_dev_dbg_close(struct nbd_device *nbd)
 {
 }
 
 static int nbd_dbg_init(void)
 {
     return 0;
 }
 
 static void nbd_dbg_close(void)
 {
 }
 
 #endif
 
 static int nbd_init_request(struct blk_mq_tag_set *set, struct request *rq,
                 unsigned int hctx_idx, unsigned int numa_node)
 {
     struct nbd_cmd *cmd = blk_mq_rq_to_pdu(rq);
     cmd->nbd = set->driver_data;
     cmd->flags = 0;
     mutex_init(&cmd->lock);
     return 0;
 }
 
 static const struct blk_mq_ops nbd_mq_ops = {
     .queue_rq   = nbd_queue_rq,
     .complete   = nbd_complete_rq,
     .init_request   = nbd_init_request,
     .timeout    = nbd_xmit_timeout,
 };
 
 static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
 {
     struct nbd_device *nbd;
     struct gendisk *disk;
     int err = -ENOMEM;
 
     nbd = kzalloc(sizeof(struct nbd_device), GFP_KERNEL);
     if (!nbd)
         goto out;
 
     nbd->tag_set.ops = &nbd_mq_ops;
     nbd->tag_set.nr_hw_queues = 1;
     nbd->tag_set.queue_depth = 128;
     nbd->tag_set.numa_node = NUMA_NO_NODE;
     nbd->tag_set.cmd_size = sizeof(struct nbd_cmd);
     nbd->tag_set.flags = BLK_MQ_F_SHOULD_MERGE |
         BLK_MQ_F_BLOCKING;
     nbd->tag_set.driver_data = nbd;
     INIT_WORK(&nbd->remove_work, nbd_dev_remove_work);
     nbd->backend = NULL;
 
     err = blk_mq_alloc_tag_set(&nbd->tag_set);
     if (err)
         goto out_free_nbd;
 
     mutex_lock(&nbd_index_mutex);
     if (index >= 0) {
         err = idr_alloc(&nbd_index_idr, nbd, index, index + 1,
                 GFP_KERNEL);
         if (err == -ENOSPC)
             err = -EEXIST;
     } else {
         err = idr_alloc(&nbd_index_idr, nbd, 0, 0, GFP_KERNEL);
         if (err >= 0)
             index = err;
     }
     nbd->index = index;
     mutex_unlock(&nbd_index_mutex);
     if (err < 0)
         goto out_free_tags;
 
     disk = blk_mq_alloc_disk(&nbd->tag_set, NULL);
     if (IS_ERR(disk)) {
         err = PTR_ERR(disk);
         goto out_free_idr;
     }
     nbd->disk = disk;
 
     nbd->recv_workq = alloc_workqueue("nbd%d-recv",
                       WQ_MEM_RECLAIM | WQ_HIGHPRI |
                       WQ_UNBOUND, 0, nbd->index);
     if (!nbd->recv_workq) {
         dev_err(disk_to_dev(nbd->disk), "Could not allocate knbd recv work queue.\n");
         err = -ENOMEM;
         goto out_err_disk;
     }
 
     /*
      * Tell the block layer that we are not a rotational device
      */
     blk_queue_flag_set(QUEUE_FLAG_NONROT, disk->queue);
     blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, disk->queue);
     disk->queue->limits.discard_granularity = 0;
     blk_queue_max_discard_sectors(disk->queue, 0);
     blk_queue_max_segment_size(disk->queue, UINT_MAX);
     blk_queue_max_segments(disk->queue, USHRT_MAX);
     blk_queue_max_hw_sectors(disk->queue, 65536);
     disk->queue->limits.max_sectors = 256;
 
     mutex_init(&nbd->config_lock);
     refcount_set(&nbd->config_refs, 0);
     /*
      * Start out with a zero references to keep other threads from using
      * this device until it is fully initialized.
      */
     refcount_set(&nbd->refs, 0);
     INIT_LIST_HEAD(&nbd->list);
     disk->major = NBD_MAJOR;
     disk->first_minor = index << part_shift;
     disk->minors = 1 << part_shift;
     disk->fops = &nbd_fops;
     disk->private_data = nbd;
     sprintf(disk->disk_name, "nbd%d", index);
     err = add_disk(disk);
     if (err)
         goto out_free_work;
 
     /*
      * Now publish the device.
      */
     refcount_set(&nbd->refs, refs);
     nbd_total_devices++;
     return nbd;
 
 out_free_work:
     destroy_workqueue(nbd->recv_workq);
 out_err_disk:
     put_disk(disk);
 out_free_idr:
     mutex_lock(&nbd_index_mutex);
     idr_remove(&nbd_index_idr, index);
     mutex_unlock(&nbd_index_mutex);
 out_free_tags:
     blk_mq_free_tag_set(&nbd->tag_set);
 out_free_nbd:
     kfree(nbd);
 out:
     return ERR_PTR(err);
 }
 
 static struct nbd_device *nbd_find_get_unused(void)
 {
     struct nbd_device *nbd;
     int id;
 
     lockdep_assert_held(&nbd_index_mutex);
 
     idr_for_each_entry(&nbd_index_idr, nbd, id) {
         if (refcount_read(&nbd->config_refs) ||
             test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags))
             continue;
         if (refcount_inc_not_zero(&nbd->refs))
             return nbd;
     }
 
     return NULL;
 }
 
 /* Netlink interface. */
 static const struct nla_policy nbd_attr_policy[NBD_ATTR_MAX + 1] = {
     [NBD_ATTR_INDEX]        =   { .type = NLA_U32 },
     [NBD_ATTR_SIZE_BYTES]       =   { .type = NLA_U64 },
     [NBD_ATTR_BLOCK_SIZE_BYTES] =   { .type = NLA_U64 },
     [NBD_ATTR_TIMEOUT]      =   { .type = NLA_U64 },
     [NBD_ATTR_SERVER_FLAGS]     =   { .type = NLA_U64 },
     [NBD_ATTR_CLIENT_FLAGS]     =   { .type = NLA_U64 },
     [NBD_ATTR_SOCKETS]      =   { .type = NLA_NESTED},
     [NBD_ATTR_DEAD_CONN_TIMEOUT]    =   { .type = NLA_U64 },
     [NBD_ATTR_DEVICE_LIST]      =   { .type = NLA_NESTED},
     [NBD_ATTR_BACKEND_IDENTIFIER]   =   { .type = NLA_STRING},
 };
 
 static const struct nla_policy nbd_sock_policy[NBD_SOCK_MAX + 1] = {
     [NBD_SOCK_FD]           =   { .type = NLA_U32 },
 };
 
 /* We don't use this right now since we don't parse the incoming list, but we
  * still want it here so userspace knows what to expect.
  */
 static const struct nla_policy __attribute__((unused))
 nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = {
     [NBD_DEVICE_INDEX]      =   { .type = NLA_U32 },
     [NBD_DEVICE_CONNECTED]      =   { .type = NLA_U8 },
 };
 
 static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd)
 {
     struct nbd_config *config = nbd->config;
     u64 bsize = nbd_blksize(config);
     u64 bytes = config->bytesize;
 
     if (info->attrs[NBD_ATTR_SIZE_BYTES])
         bytes = nla_get_u64(info->attrs[NBD_ATTR_SIZE_BYTES]);
 
     if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES])
         bsize = nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
 
     if (bytes != config->bytesize || bsize != nbd_blksize(config))
         return nbd_set_size(nbd, bytes, bsize);
     return 0;
 }
 
 static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
 {
     struct nbd_device *nbd;
     struct nbd_config *config;
     int index = -1;
     int ret;
     bool put_dev = false;
 
     if (!netlink_capable(skb, CAP_SYS_ADMIN))
         return -EPERM;
 
     if (info->attrs[NBD_ATTR_INDEX]) {
         index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
 
         /*
          * Too big first_minor can cause duplicate creation of
          * sysfs files/links, since index << part_shift might overflow, or
          * MKDEV() expect that the max bits of first_minor is 20.
          */
         if (index < 0 || index > MINORMASK >> part_shift) {
             pr_err("illegal input index %d\n", index);
             return -EINVAL;
         }
     }
     if (!info->attrs[NBD_ATTR_SOCKETS]) {
         pr_err("must specify at least one socket\n");
         return -EINVAL;
     }
     if (!info->attrs[NBD_ATTR_SIZE_BYTES]) {
         pr_err("must specify a size in bytes for the device\n");
         return -EINVAL;
     }
 again:
     mutex_lock(&nbd_index_mutex);
     if (index == -1) {
         nbd = nbd_find_get_unused();
     } else {
         nbd = idr_find(&nbd_index_idr, index);
         if (nbd) {
             if ((test_bit(NBD_DESTROY_ON_DISCONNECT, &nbd->flags) &&
                  test_bit(NBD_DISCONNECT_REQUESTED, &nbd->flags)) ||
                 !refcount_inc_not_zero(&nbd->refs)) {
                 mutex_unlock(&nbd_index_mutex);
                 pr_err("device at index %d is going down\n",
                     index);
                 return -EINVAL;
             }
         }
     }
     mutex_unlock(&nbd_index_mutex);
 
     if (!nbd) {
         nbd = nbd_dev_add(index, 2);
         if (IS_ERR(nbd)) {
             pr_err("failed to add new device\n");
             return PTR_ERR(nbd);
         }
     }
 
     mutex_lock(&nbd->config_lock);
     if (refcount_read(&nbd->config_refs)) {
         mutex_unlock(&nbd->config_lock);
         nbd_put(nbd);
         if (index == -1)
             goto again;
         pr_err("nbd%d already in use\n", index);
         return -EBUSY;
     }
     if (WARN_ON(nbd->config)) {
         mutex_unlock(&nbd->config_lock);
         nbd_put(nbd);
         return -EINVAL;
     }
     config = nbd_alloc_config();
     if (IS_ERR(config)) {
         mutex_unlock(&nbd->config_lock);
         nbd_put(nbd);
         pr_err("couldn't allocate config\n");
         return PTR_ERR(config);
     }
     nbd->config = config;
     refcount_set(&nbd->config_refs, 1);
     set_bit(NBD_RT_BOUND, &config->runtime_flags);
 
     ret = nbd_genl_size_set(info, nbd);
     if (ret)
         goto out;
 
     if (info->attrs[NBD_ATTR_TIMEOUT])
         nbd_set_cmd_timeout(nbd,
                     nla_get_u64(info->attrs[NBD_ATTR_TIMEOUT]));
     if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {
         config->dead_conn_timeout =
             nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);
         config->dead_conn_timeout *= HZ;
     }
     if (info->attrs[NBD_ATTR_SERVER_FLAGS])
         config->flags =
             nla_get_u64(info->attrs[NBD_ATTR_SERVER_FLAGS]);
     if (info->attrs[NBD_ATTR_CLIENT_FLAGS]) {
         u64 flags = nla_get_u64(info->attrs[NBD_ATTR_CLIENT_FLAGS]);
         if (flags & NBD_CFLAG_DESTROY_ON_DISCONNECT) {
             /*
              * We have 1 ref to keep the device around, and then 1
              * ref for our current operation here, which will be
              * inherited by the config.  If we already have
              * DESTROY_ON_DISCONNECT set then we know we don't have
              * that extra ref already held so we don't need the
              * put_dev.
              */
             if (!test_and_set_bit(NBD_DESTROY_ON_DISCONNECT,
                           &nbd->flags))
                 put_dev = true;
         } else {
             if (test_and_clear_bit(NBD_DESTROY_ON_DISCONNECT,
                            &nbd->flags))
                 refcount_inc(&nbd->refs);
         }
         if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
             set_bit(NBD_RT_DISCONNECT_ON_CLOSE,
                 &config->runtime_flags);
         }
     }
 
     if (info->attrs[NBD_ATTR_SOCKETS]) {
         struct nlattr *attr;
         int rem, fd;
 
         nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS],
                     rem) {
             struct nlattr *socks[NBD_SOCK_MAX+1];
 
             if (nla_type(attr) != NBD_SOCK_ITEM) {
                 pr_err("socks must be embedded in a SOCK_ITEM attr\n");
                 ret = -EINVAL;
                 goto out;
             }
             ret = nla_parse_nested_deprecated(socks, NBD_SOCK_MAX,
                               attr,
                               nbd_sock_policy,
                               info->extack);
             if (ret != 0) {
                 pr_err("error processing sock list\n");
                 ret = -EINVAL;
                 goto out;
             }
             if (!socks[NBD_SOCK_FD])
                 continue;
             fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
             ret = nbd_add_socket(nbd, fd, true);
             if (ret)
                 goto out;
         }
     }
     ret = nbd_start_device(nbd);
     if (ret)
         goto out;
     if (info->attrs[NBD_ATTR_BACKEND_IDENTIFIER]) {
         nbd->backend = nla_strdup(info->attrs[NBD_ATTR_BACKEND_IDENTIFIER],
                       GFP_KERNEL);
         if (!nbd->backend) {
             ret = -ENOMEM;
             goto out;
         }
     }
     ret = device_create_file(disk_to_dev(nbd->disk), &backend_attr);
     if (ret) {
         dev_err(disk_to_dev(nbd->disk),
             "device_create_file failed for backend!\n");
         goto out;
     }
     set_bit(NBD_RT_HAS_BACKEND_FILE, &config->runtime_flags);
 out:
     mutex_unlock(&nbd->config_lock);
     if (!ret) {
         set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags);
         refcount_inc(&nbd->config_refs);
         nbd_connect_reply(info, nbd->index);
     }
     nbd_config_put(nbd);
     if (put_dev)
         nbd_put(nbd);
     return ret;
 }
 
 static void nbd_disconnect_and_put(struct nbd_device *nbd)
 {
     mutex_lock(&nbd->config_lock);
     nbd_disconnect(nbd);
     sock_shutdown(nbd);
     wake_up(&nbd->config->conn_wait);
     /*
      * Make sure recv thread has finished, we can safely call nbd_clear_que()
      * to cancel the inflight I/Os.
      */
     flush_workqueue(nbd->recv_workq);
     nbd_clear_que(nbd);
     nbd->task_setup = NULL;
     mutex_unlock(&nbd->config_lock);
 
     if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF,
                    &nbd->config->runtime_flags))
         nbd_config_put(nbd);
 }
 
 static int nbd_genl_disconnect(struct sk_buff *skb, struct genl_info *info)
 {
     struct nbd_device *nbd;
     int index;
 
     if (!netlink_capable(skb, CAP_SYS_ADMIN))
         return -EPERM;
 
     if (!info->attrs[NBD_ATTR_INDEX]) {
         pr_err("must specify an index to disconnect\n");
         return -EINVAL;
     }
     index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
     mutex_lock(&nbd_index_mutex);
     nbd = idr_find(&nbd_index_idr, index);
     if (!nbd) {
         mutex_unlock(&nbd_index_mutex);
         pr_err("couldn't find device at index %d\n", index);
         return -EINVAL;
     }
     if (!refcount_inc_not_zero(&nbd->refs)) {
         mutex_unlock(&nbd_index_mutex);
         pr_err("device at index %d is going down\n", index);
         return -EINVAL;
     }
     mutex_unlock(&nbd_index_mutex);
     if (!refcount_inc_not_zero(&nbd->config_refs))
         goto put_nbd;
     nbd_disconnect_and_put(nbd);
     nbd_config_put(nbd);
 put_nbd:
     nbd_put(nbd);
     return 0;
 }
 
 static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info)
 {
     struct nbd_device *nbd = NULL;
     struct nbd_config *config;
     int index;
     int ret = 0;
     bool put_dev = false;
 
     if (!netlink_capable(skb, CAP_SYS_ADMIN))
         return -EPERM;
 
     if (!info->attrs[NBD_ATTR_INDEX]) {
         pr_err("must specify a device to reconfigure\n");
         return -EINVAL;
     }
     index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
     mutex_lock(&nbd_index_mutex);
     nbd = idr_find(&nbd_index_idr, index);
     if (!nbd) {
         mutex_unlock(&nbd_index_mutex);
         pr_err("couldn't find a device at index %d\n", index);
         return -EINVAL;
     }
     if (nbd->backend) {
         if (info->attrs[NBD_ATTR_BACKEND_IDENTIFIER]) {
             if (nla_strcmp(info->attrs[NBD_ATTR_BACKEND_IDENTIFIER],
                        nbd->backend)) {
                 mutex_unlock(&nbd_index_mutex);
                 dev_err(nbd_to_dev(nbd),
                     "backend image doesn't match with %s\n",
                     nbd->backend);
                 return -EINVAL;
             }
         } else {
             mutex_unlock(&nbd_index_mutex);
             dev_err(nbd_to_dev(nbd), "must specify backend\n");
             return -EINVAL;
         }
     }
     if (!refcount_inc_not_zero(&nbd->refs)) {
         mutex_unlock(&nbd_index_mutex);
         pr_err("device at index %d is going down\n", index);
         return -EINVAL;
     }
     mutex_unlock(&nbd_index_mutex);
 
     if (!refcount_inc_not_zero(&nbd->config_refs)) {
         dev_err(nbd_to_dev(nbd),
             "not configured, cannot reconfigure\n");
         nbd_put(nbd);
         return -EINVAL;
     }
 
     mutex_lock(&nbd->config_lock);
     config = nbd->config;
     if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) ||
         !nbd->pid) {
         dev_err(nbd_to_dev(nbd),
             "not configured, cannot reconfigure\n");
         ret = -EINVAL;
         goto out;
     }
 
     ret = nbd_genl_size_set(info, nbd);
     if (ret)
         goto out;
 
     if (info->attrs[NBD_ATTR_TIMEOUT])
         nbd_set_cmd_timeout(nbd,
                     nla_get_u64(info->attrs[NBD_ATTR_TIMEOUT]));
     if (info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]) {
         config->dead_conn_timeout =
             nla_get_u64(info->attrs[NBD_ATTR_DEAD_CONN_TIMEOUT]);
         config->dead_conn_timeout *= HZ;
     }
     if (info->attrs[NBD_ATTR_CLIENT_FLAGS]) {
         u64 flags = nla_get_u64(info->attrs[NBD_ATTR_CLIENT_FLAGS]);
         if (flags & NBD_CFLAG_DESTROY_ON_DISCONNECT) {
             if (!test_and_set_bit(NBD_DESTROY_ON_DISCONNECT,
                           &nbd->flags))
                 put_dev = true;
         } else {
             if (test_and_clear_bit(NBD_DESTROY_ON_DISCONNECT,
                            &nbd->flags))
                 refcount_inc(&nbd->refs);
         }
 
         if (flags & NBD_CFLAG_DISCONNECT_ON_CLOSE) {
             set_bit(NBD_RT_DISCONNECT_ON_CLOSE,
                     &config->runtime_flags);
         } else {
             clear_bit(NBD_RT_DISCONNECT_ON_CLOSE,
                     &config->runtime_flags);
         }
     }
 
     if (info->attrs[NBD_ATTR_SOCKETS]) {
         struct nlattr *attr;
         int rem, fd;
 
         nla_for_each_nested(attr, info->attrs[NBD_ATTR_SOCKETS],
                     rem) {
             struct nlattr *socks[NBD_SOCK_MAX+1];
 
             if (nla_type(attr) != NBD_SOCK_ITEM) {
                 pr_err("socks must be embedded in a SOCK_ITEM attr\n");
                 ret = -EINVAL;
                 goto out;
             }
             ret = nla_parse_nested_deprecated(socks, NBD_SOCK_MAX,
                               attr,
                               nbd_sock_policy,
                               info->extack);
             if (ret != 0) {
                 pr_err("error processing sock list\n");
                 ret = -EINVAL;
                 goto out;
             }
             if (!socks[NBD_SOCK_FD])
                 continue;
             fd = (int)nla_get_u32(socks[NBD_SOCK_FD]);
             ret = nbd_reconnect_socket(nbd, fd);
             if (ret) {
                 if (ret == -ENOSPC)
                     ret = 0;
                 goto out;
             }
             dev_info(nbd_to_dev(nbd), "reconnected socket\n");
         }
     }
 out:
     mutex_unlock(&nbd->config_lock);
     nbd_config_put(nbd);
     nbd_put(nbd);
     if (put_dev)
         nbd_put(nbd);
     return ret;
 }
 
 static const struct genl_small_ops nbd_connect_genl_ops[] = {
     {
         .cmd    = NBD_CMD_CONNECT,
         .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
         .doit   = nbd_genl_connect,
     },
     {
         .cmd    = NBD_CMD_DISCONNECT,
         .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
         .doit   = nbd_genl_disconnect,
     },
     {
         .cmd    = NBD_CMD_RECONFIGURE,
         .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
         .doit   = nbd_genl_reconfigure,
     },
     {
         .cmd    = NBD_CMD_STATUS,
         .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
         .doit   = nbd_genl_status,
     },
 };
 
 static const struct genl_multicast_group nbd_mcast_grps[] = {
     { .name = NBD_GENL_MCAST_GROUP_NAME, },
 };
 
 static struct genl_family nbd_genl_family __ro_after_init = {
     .hdrsize    = 0,
     .name       = NBD_GENL_FAMILY_NAME,
     .version    = NBD_GENL_VERSION,
     .module     = THIS_MODULE,
     .small_ops  = nbd_connect_genl_ops,
     .n_small_ops    = ARRAY_SIZE(nbd_connect_genl_ops),
     .maxattr    = NBD_ATTR_MAX,
     .policy = nbd_attr_policy,
     .mcgrps     = nbd_mcast_grps,
     .n_mcgrps   = ARRAY_SIZE(nbd_mcast_grps),
 };
 
 static int populate_nbd_status(struct nbd_device *nbd, struct sk_buff *reply)
 {
     struct nlattr *dev_opt;
     u8 connected = 0;
     int ret;
 
     /* This is a little racey, but for status it's ok.  The
      * reason we don't take a ref here is because we can't
      * take a ref in the index == -1 case as we would need
      * to put under the nbd_index_mutex, which could
      * deadlock if we are configured to remove ourselves
      * once we're disconnected.
      */
     if (refcount_read(&nbd->config_refs))
         connected = 1;
     dev_opt = nla_nest_start_noflag(reply, NBD_DEVICE_ITEM);
     if (!dev_opt)
         return -EMSGSIZE;
     ret = nla_put_u32(reply, NBD_DEVICE_INDEX, nbd->index);
     if (ret)
         return -EMSGSIZE;
     ret = nla_put_u8(reply, NBD_DEVICE_CONNECTED,
              connected);
     if (ret)
         return -EMSGSIZE;
     nla_nest_end(reply, dev_opt);
     return 0;
 }
 
 static int status_cb(int id, void *ptr, void *data)
 {
     struct nbd_device *nbd = ptr;
     return populate_nbd_status(nbd, (struct sk_buff *)data);
 }
 
 static int nbd_genl_status(struct sk_buff *skb, struct genl_info *info)
 {
     struct nlattr *dev_list;
     struct sk_buff *reply;
     void *reply_head;
     size_t msg_size;
     int index = -1;
     int ret = -ENOMEM;
 
     if (info->attrs[NBD_ATTR_INDEX])
         index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
 
     mutex_lock(&nbd_index_mutex);
 
     msg_size = nla_total_size(nla_attr_size(sizeof(u32)) +
                   nla_attr_size(sizeof(u8)));
     msg_size *= (index == -1) ? nbd_total_devices : 1;
 
     reply = genlmsg_new(msg_size, GFP_KERNEL);
     if (!reply)
         goto out;
     reply_head = genlmsg_put_reply(reply, info, &nbd_genl_family, 0,
                        NBD_CMD_STATUS);
     if (!reply_head) {
         nlmsg_free(reply);
         goto out;
     }
 
     dev_list = nla_nest_start_noflag(reply, NBD_ATTR_DEVICE_LIST);
     if (index == -1) {
         ret = idr_for_each(&nbd_index_idr, &status_cb, reply);
         if (ret) {
             nlmsg_free(reply);
             goto out;
         }
     } else {
         struct nbd_device *nbd;
         nbd = idr_find(&nbd_index_idr, index);
         if (nbd) {
             ret = populate_nbd_status(nbd, reply);
             if (ret) {
                 nlmsg_free(reply);
                 goto out;
             }
         }
     }
     nla_nest_end(reply, dev_list);
     genlmsg_end(reply, reply_head);
     ret = genlmsg_reply(reply, info);
 out:
     mutex_unlock(&nbd_index_mutex);
     return ret;
 }
 
 static void nbd_connect_reply(struct genl_info *info, int index)
 {
     struct sk_buff *skb;
     void *msg_head;
     int ret;
 
     skb = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
     if (!skb)
         return;
     msg_head = genlmsg_put_reply(skb, info, &nbd_genl_family, 0,
                      NBD_CMD_CONNECT);
     if (!msg_head) {
         nlmsg_free(skb);
         return;
     }
     ret = nla_put_u32(skb, NBD_ATTR_INDEX, index);
     if (ret) {
         nlmsg_free(skb);
         return;
     }
     genlmsg_end(skb, msg_head);
     genlmsg_reply(skb, info);
 }
 
 static void nbd_mcast_index(int index)
 {
     struct sk_buff *skb;
     void *msg_head;
     int ret;
 
     skb = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
     if (!skb)
         return;
     msg_head = genlmsg_put(skb, 0, 0, &nbd_genl_family, 0,
                      NBD_CMD_LINK_DEAD);
     if (!msg_head) {
         nlmsg_free(skb);
         return;
     }
     ret = nla_put_u32(skb, NBD_ATTR_INDEX, index);
     if (ret) {
         nlmsg_free(skb);
         return;
     }
     genlmsg_end(skb, msg_head);
     genlmsg_multicast(&nbd_genl_family, skb, 0, 0, GFP_KERNEL);
 }
 
 static void nbd_dead_link_work(struct work_struct *work)
 {
     struct link_dead_args *args = container_of(work, struct link_dead_args,
                            work);
     nbd_mcast_index(args->index);
     kfree(args);
 }
 
 static int __init nbd_init(void)
 {
     int i;
 
     BUILD_BUG_ON(sizeof(struct nbd_request) != 28);
 
     if (max_part < 0) {
         pr_err("max_part must be >= 0\n");
         return -EINVAL;
     }
 
     part_shift = 0;
     if (max_part > 0) {
         part_shift = fls(max_part);
 
         /*
          * Adjust max_part according to part_shift as it is exported
          * to user space so that user can know the max number of
          * partition kernel should be able to manage.
          *
          * Note that -1 is required because partition 0 is reserved
          * for the whole disk.
          */
         max_part = (1UL << part_shift) - 1;
     }
 
     if ((1UL << part_shift) > DISK_MAX_PARTS)
         return -EINVAL;
 
     if (nbds_max > 1UL << (MINORBITS - part_shift))
         return -EINVAL;
 
     if (register_blkdev(NBD_MAJOR, "nbd"))
         return -EIO;
 
     nbd_del_wq = alloc_workqueue("nbd-del", WQ_UNBOUND, 0);
     if (!nbd_del_wq) {
         unregister_blkdev(NBD_MAJOR, "nbd");
         return -ENOMEM;
     }
 
     if (genl_register_family(&nbd_genl_family)) {
         destroy_workqueue(nbd_del_wq);
         unregister_blkdev(NBD_MAJOR, "nbd");
         return -EINVAL;
     }
     nbd_dbg_init();
 
     for (i = 0; i < nbds_max; i++)
         nbd_dev_add(i, 1);
     return 0;
 }
 
 static int nbd_exit_cb(int id, void *ptr, void *data)
 {
     struct list_head *list = (struct list_head *)data;
     struct nbd_device *nbd = ptr;
 
     /* Skip nbd that is being removed asynchronously */
     if (refcount_read(&nbd->refs))
         list_add_tail(&nbd->list, list);
 
     return 0;
 }
 
 static void __exit nbd_cleanup(void)
 {
     struct nbd_device *nbd;
     LIST_HEAD(del_list);
 
     /*
      * Unregister netlink interface prior to waiting
      * for the completion of netlink commands.
      */
     genl_unregister_family(&nbd_genl_family);
 
     nbd_dbg_close();
 
     mutex_lock(&nbd_index_mutex);
     idr_for_each(&nbd_index_idr, &nbd_exit_cb, &del_list);
     mutex_unlock(&nbd_index_mutex);
 
     while (!list_empty(&del_list)) {
         nbd = list_first_entry(&del_list, struct nbd_device, list);
         list_del_init(&nbd->list);
         if (refcount_read(&nbd->config_refs))
             pr_err("possibly leaking nbd_config (ref %d)\n",
                     refcount_read(&nbd->config_refs));
         if (refcount_read(&nbd->refs) != 1)
             pr_err("possibly leaking a device\n");
         nbd_put(nbd);
     }
 
     /* Also wait for nbd_dev_remove_work() completes */
     destroy_workqueue(nbd_del_wq);
 
     idr_destroy(&nbd_index_idr);
     unregister_blkdev(NBD_MAJOR, "nbd");
 }
 
 module_init(nbd_init);
 module_exit(nbd_cleanup);
 
 MODULE_DESCRIPTION("Network Block Device");
 MODULE_LICENSE("GPL");
 
 module_param(nbds_max, int, 0444);
 MODULE_PARM_DESC(nbds_max, "number of network block devices to initialize (default: 16)");
 module_param(max_part, int, 0444);
 MODULE_PARM_DESC(max_part, "number of partitions per device (default: 16)");