linux-kernel - [PATCH] nbd: ratelimit error msgs after socket close

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Date:	Thu, 14 Jan 2016 13:42:32 -0500
From:	Dan Streetman <dan.streetman@...onical.com>
To:	Markus Pargmann <mpa@...gutronix.de>, Jens Axboe <axboe@...com>
Cc:	nbd-general@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Dan Streetman <ddstreet@...e.org>,
	Dan Streetman <dan.streetman@...onical.com>
Subject: [PATCH] nbd: ratelimit error msgs after socket close

Make the "Attempted send on closed socket" error messages generated in
nbd_request_handler() ratelimited.

When the nbd socket is shutdown, the nbd_request_handler() function emits
an error message for every request remaining in its queue.  If the queue
is large, this will spam a large amount of messages to the log.  There's
no need for a separate error message for each request, so this patch
ratelimits it.

In the specific case this was found, the system was virtual and the error
messages were logged to the serial port, which overwhelmed it.

Fixes: 4d48a542b427 ("nbd: fix I/O hang on disconnected nbds")
Signed-off-by: Dan Streetman <dan.streetman@...onical.com>
---
 drivers/block/nbd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index e4c5cc1..c65d41f 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -618,8 +618,8 @@ static void nbd_request_handler(struct request_queue *q)
 			req, req->cmd_type);

 		if (unlikely(!nbd->sock)) {
-			dev_err(disk_to_dev(nbd->disk),
-				"Attempted send on closed socket\n");
+			dev_err_ratelimited(disk_to_dev(nbd->disk),
+					    "Attempted send on closed socket\n");
 			req->errors++;
 			nbd_end_request(nbd, req);
 			spin_lock_irq(q->queue_lock);
-- 
2.5.0