[3.16.y-ckt stable] Patch "dm thin: fix inability to discard blocks when in out-of-data-space mode" has been added to staging queue

[Luis Henriques]

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

    dm thin: fix inability to discard blocks when in out-of-data-space mode

to the linux-3.16.y-queue branch of the 3.16.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-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt4.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From fb5bac9df5c8ad989d39857a5cbe7fd8c752d447 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt at redhat.com>
Date: Wed, 10 Dec 2014 17:06:57 +0000
Subject: dm thin: fix inability to discard blocks when in out-of-data-space
 mode

commit 45ec9bd0fd7abf8705e7cf12205ff69fe9d51181 upstream.

When the pool was in PM_OUT_OF_SPACE mode its process_prepared_discard
function pointer was incorrectly being set to
process_prepared_discard_passdown rather than process_prepared_discard.

This incorrect function pointer meant the discard was being passed down,
but not effecting the mapping.  As such any discard that was issued, in
an attempt to reclaim blocks, would not successfully free data space.

Reported-by: Eric Sandeen <sandeen at redhat.com>
Signed-off-by: Joe Thornber <ejt at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/dm-thin.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 6f75083a81cc..c13efb1020d9 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1759,7 +1759,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 		pool->process_bio = process_bio_read_only;
 		pool->process_discard = process_discard;
 		pool->process_prepared_mapping = process_prepared_mapping;
-		pool->process_prepared_discard = process_prepared_discard_passdown;
+		pool->process_prepared_discard = process_prepared_discard;

 		if (!pool->pf.error_if_no_space && no_space_timeout)
 			queue_delayed_work(pool->wq, &pool->no_space_timeout, no_space_timeout);
--
2.1.4