nbd: don't requeue the same request twice.

We can race with the snd timeout and the per-request timeout and end up
requeuing the same request twice.  We can't use the send_complete
completion to tell if everything is ok because we hold the tx_lock
during send, so the timeout stuff will block waiting to mark the socket
dead, and we could be marked complete and still requeue.  Instead add a
flag to the socket so we know whether we've been requeued yet.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 3 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 74a05561b620..f8cf7d4cca7f 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -112,12 +112,15 @@ struct nbd_device {
         struct task_struct *task_setup;
 };
 
+#define NBD_CMD_REQUEUED        1
+
 struct nbd_cmd {
         struct nbd_device *nbd;
         int index;
         int cookie;
         struct completion send_complete;
         blk_status_t status;
+        unsigned long flags;
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -146,6 +149,14 @@ 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);
+}
+
 static const char *nbdcmd_to_ascii(int cmd)
 {
         switch (cmd) {
@@ -343,7 +354,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
                                         nbd_mark_nsock_dead(nbd, nsock, 1);
                                 mutex_unlock(&nsock->tx_lock);
                         }
-                        blk_mq_requeue_request(req, true);
+                        nbd_requeue_cmd(cmd);
                         nbd_config_put(nbd);
                         return BLK_EH_DONE;
                 }
@@ -500,6 +511,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
                                 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),
@@ -541,6 +553,7 @@ send_pages:
                                          */
                                         nsock->pending = req;
                                         nsock->sent = sent;
+                                        set_bit(NBD_CMD_REQUEUED, &cmd->flags);
                                         return BLK_STS_RESOURCE;
                                 }
                                 dev_err(disk_to_dev(nbd->disk),
@@ -805,7 +818,7 @@ again:
          */
         blk_mq_start_request(req);
         if (unlikely(nsock->pending && nsock->pending != req)) {
-                blk_mq_requeue_request(req, true);
+                nbd_requeue_cmd(cmd);
                 ret = 0;
                 goto out;
         }
@@ -818,7 +831,7 @@ again:
                 dev_err_ratelimited(disk_to_dev(nbd->disk),
                                     "Request send failed, requeueing\n");
                 nbd_mark_nsock_dead(nbd, nsock, 1);
-                blk_mq_requeue_request(req, true);
+                nbd_requeue_cmd(cmd);
                 ret = 0;
         }
 out:
@@ -843,6 +856,7 @@ static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
          * done sending everything over the wire.
          */
         init_completion(&cmd->send_complete);
+        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
@@ -1460,6 +1474,7 @@ static int nbd_init_request(struct blk_mq_tag_set *set, struct request *rq,
 {
         struct nbd_cmd *cmd = blk_mq_rq_to_pdu(rq);
         cmd->nbd = set->driver_data;
+        cmd->flags = 0;
         return 0;
 }