[PATCH] nbd: add a missed nbd_config_put() in nbd_xmit_timeout()

[Sun Ke]

When try to get the lock failed, before return, execute the
nbd_config_put() to decrease the nbd->config_refs.

If the nbd->config_refs is added but not decreased. Then will not
execute nbd_clear_sock() in nbd_config_put(). bd->task_setup will
not be cleared away. Finally, print"Device being setup by another
task" in nbd_add_sock() and nbd device can not be reused.

Fixes: 8f3ea35929a0 ("nbd: handle unexpected replies better")
Signed-off-by: Sun Ke <sunke32@xxxxxxxxxx>
---
 drivers/block/nbd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index e21d2de..a69a90a 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -357,8 +357,10 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
 	}
 	config = nbd->config;
 
-	if (!mutex_trylock(&cmd->lock))
+	if (!mutex_trylock(&cmd->lock)) {
+		nbd_config_put(nbd);
 		return BLK_EH_RESET_TIMER;
+	}
 
 	if (config->num_connections > 1) {
 		dev_err_ratelimited(nbd_to_dev(nbd),
-- 
2.7.4