]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
dm cache: fix race affecting dirty block count
authorAnssi Hannula <anssi.hannula@iki.fi>
Fri, 1 Aug 2014 15:55:47 +0000 (11:55 -0400)
committerMike Snitzer <snitzer@redhat.com>
Fri, 1 Aug 2014 16:25:22 +0000 (12:25 -0400)
commit44fa816bb778edbab6b6ddaaf24908dd6295937e
tree2b67384ea2670780a7215c593b08e2ec92bd27e6
parentd8c712ea471ce7a4fd1734ad2211adf8469ddddc
dm cache: fix race affecting dirty block count

nr_dirty is updated without locking, causing it to drift so that it is
non-zero (either a small positive integer, or a very large one when an
underflow occurs) even when there are no actual dirty blocks.  This was
due to a race between the workqueue and map function accessing nr_dirty
in parallel without proper protection.

People were seeing under runs due to a race on increment/decrement of
nr_dirty, see: https://lkml.org/lkml/2014/6/3/648

Fix this by using an atomic_t for nr_dirty.

Reported-by: roma1390@gmail.com
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
drivers/md/dm-cache-target.c