linux-kernel - [PATCH 4.2.y-ckt 206/218] nbd: ratelimit error msgs after socket close

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Message-Id: <1459455431-12687-207-git-send-email-kamal@canonical.com>
Date:	Thu, 31 Mar 2016 13:16:59 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Dan Streetman <dan.streetman@...onical.com>,
	Markus Pargmann <mpa@...gutronix.de>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 206/218] nbd: ratelimit error msgs after socket close

4.2.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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: Kamal Mostafa <kamal@...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 0e385d8..e7bd163 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -556,8 +556,8 @@ static void do_nbd_request(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);
-- 
2.7.4