[4.2.y-ckt stable] Patch "nbd: ratelimit error msgs after socket close" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    nbd: ratelimit error msgs after socket close

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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

>From b38c04446d98efa23e4971e1edc66501253cdafb Mon Sep 17 00:00:00 2001
From: Dan Streetman <dan.streetman at canonical.com>
Date: Thu, 14 Jan 2016 13:42:32 -0500
Subject: nbd: ratelimit error msgs after socket close

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 at canonical.com>
Signed-off-by: Markus Pargmann <mpa at pengutronix.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.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