Patch "dm cache: fix leaking of deferred bio prison cells" has been added to the 4.2-stable tree

Patch "dm cache: fix leaking of deferred bio prison cells" has been added to the 4.2-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    dm cache: fix leaking of deferred bio prison cells

to the 4.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-cache-fix-leaking-of-deferred-bio-prison-cells.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9153df7405ae04c1b0466de720e0a685cfea1a3a Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Mon, 31 Aug 2015 18:20:08 +0100
Subject: dm cache: fix leaking of deferred bio prison cells

From: Joe Thornber <ejt@redhat.com>

commit 9153df7405ae04c1b0466de720e0a685cfea1a3a upstream.

There were two cases where dm_cell_visit_release() was being called,
which removes the cell from the prison's rbtree, but the callers didn't
also return the cell to the mempool.  Fix this by having them call
free_prison_cell().

This leak manifested as the 'kmalloc-96' slab growing until OOM.

Fixes: 651f5fa2a3 ("dm cache: defer whole cells")
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-cache-target.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -1729,6 +1729,8 @@ static void remap_cell_to_origin_clear_d
 		remap_to_origin(cache, bio);
 		issue(cache, bio);
 	}
+
+	free_prison_cell(cache, cell);
 }
 
 static void remap_cell_to_cache_dirty(struct cache *cache, struct dm_bio_prison_cell *cell,
@@ -1763,6 +1765,8 @@ static void remap_cell_to_cache_dirty(st
 		remap_to_cache(cache, bio, cblock);
 		issue(cache, bio);
 	}
+
+	free_prison_cell(cache, cell);
 }
 
 /*----------------------------------------------------------------*/


Patches currently in stable-queue which might be from ejt@redhat.com are

queue-4.2/dm-cache-fix-leaking-of-deferred-bio-prison-cells.patch