[3.13.y-ckt stable] Patch "nfs: Don't busy-wait on SIGKILL in __nfs_iocounter_wait" has been added to staging queue

[Kamal Mostafa]

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

    nfs: Don't busy-wait on SIGKILL in __nfs_iocounter_wait

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt12.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6ccba26b820d7244db030a649d778456c2719c7d Mon Sep 17 00:00:00 2001
From: David Jeffery <djeffery at redhat.com>
Date: Tue, 5 Aug 2014 11:19:42 -0400
Subject: nfs: Don't busy-wait on SIGKILL in __nfs_iocounter_wait
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 92a56555bd576c61b27a5cab9f38a33a1e9a1df5 upstream.

If a SIGKILL is sent to a task waiting in __nfs_iocounter_wait,
it will busy-wait or soft lockup in its while loop.
nfs_wait_bit_killable won't sleep, and the loop won't exit on
the error return.

Stop the busy-wait by breaking out of the loop when
nfs_wait_bit_killable returns an error.

Signed-off-by: David Jeffery <djeffery at redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust at primarydata.com>
[ kamal: backport to 3.13-stable: context ]
Cc: Moritz Mühlenhoff <muehlenhoff at univention.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/nfs/pagelist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 2ffebf2..27d7f27 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -113,7 +113,7 @@ __nfs_iocounter_wait(struct nfs_io_counter *c)
 		if (atomic_read(&c->io_count) == 0)
 			break;
 		ret = nfs_wait_bit_killable(&c->flags);
-	} while (atomic_read(&c->io_count) != 0);
+	} while (atomic_read(&c->io_count) != 0 && !ret);
 	finish_wait(wq, &q.wait);
 	return ret;
 }
--
1.9.1