From 44fa816bb778edbab6b6ddaaf24908dd6295937e Mon Sep 17 00:00:00 2001 From: Anssi Hannula Date: Fri, 1 Aug 2014 11:55:47 -0400 Subject: [PATCH] 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 Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- Reading git-format-patch failed