While handling a response message from server, nbd_read_stat() will
try to get request by tag, and then complete the request. However,
this is problematic if nbd haven't sent a corresponding request
message:
t1 t2
submit_bio
nbd_queue_rq
blk_mq_start_request
recv_work
nbd_read_stat
blk_mq_get_rq_by_tag
blk_mq_complete_request
nbd_send_cmd
Thus add a new cmd flag 'NBD_CMD_INFLIGHT', it will be set in
nbd_send_cmd() and checked in nbd_read_stat().
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/block/nbd.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index ca54a0736090..7b9e19675224 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -127,6 +127,11 @@ struct nbd_device {
};
#define NBD_CMD_REQUEUED 1
+/*
+ * This flag will be set if nbd_send_cmd() succeed, and will be checked in
+ * normal completion.
+ */
+#define NBD_CMD_INFLIGHT 2
struct nbd_cmd {
struct nbd_device *nbd;
@@ -743,6 +748,12 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
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), "NBD_CMD_INFLIGHT is not set %d\n",
+ tag);
+ 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));
@@ -980,6 +991,8 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
* returns EAGAIN can be retried on a different socket.
*/
ret = nbd_send_cmd(nbd, cmd, index);
+ if (!ret)
+ set_bit(NBD_CMD_INFLIGHT, &cmd->flags);
if (ret == -EAGAIN) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Request send failed, requeueing\n");
--
2.31.1
