linux-kernel - [PATCH 3.16 015/217] nbd: ratelimit error msgs after socket close

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Message-ID: <lsq.1461711741.52550589@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:21 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Markus Pargmann" <mpa@...gutronix.de>,
	"Dan Streetman" <dan.streetman@...onical.com>
Subject: [PATCH 3.16 015/217] nbd: ratelimit error msgs after socket close

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Streetman <dan.streetman@...onical.com>

commit da6ccaaa79caca4f38b540b651238f87215217a2 upstream.

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>
Signed-off-by: Markus Pargmann <mpa@...gutronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/block/nbd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -578,8 +578,8 @@ static void do_nbd_request(struct reques
 		BUG_ON(nbd->magic != NBD_MAGIC);

 		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(req);
 			spin_lock_irq(q->queue_lock);