From fb4100ae7f312c3d614b37621c2b17b3b7cf65f8 Mon Sep 17 00:00:00 2001 From: Joe Thornber Date: Wed, 20 May 2015 10:30:32 +0100 Subject: dm cache: fix race when issuing a POLICY_REPLACE operation There is a race between a policy deciding to replace a cache entry, the core target writing back any dirty data from this block, and other IO threads doing IO to the same block. This sort of problem is avoided most of the time by the core target grabbing a bio prison cell before making the request to the policy. But for a demotion the core target doesn't know which block will be demoted, so can't do this in advance. Fix this demotion race by introducing a callback to the policy interface that allows the policy to grab the cell on behalf of the core target. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org --- drivers/md/dm-cache-policy-internal.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers/md/dm-cache-policy-internal.h') diff --git a/drivers/md/dm-cache-policy-internal.h b/drivers/md/dm-cache-policy-internal.h index 2256a1f24f73..c198e6defb9c 100644 --- a/drivers/md/dm-cache-policy-internal.h +++ b/drivers/md/dm-cache-policy-internal.h @@ -16,9 +16,10 @@ */ static inline int policy_map(struct dm_cache_policy *p, dm_oblock_t oblock, bool can_block, bool can_migrate, bool discarded_oblock, - struct bio *bio, struct policy_result *result) + struct bio *bio, struct policy_locker *locker, + struct policy_result *result) { - return p->map(p, oblock, can_block, can_migrate, discarded_oblock, bio, result); + return p->map(p, oblock, can_block, can_migrate, discarded_oblock, bio, locker, result); } static inline int policy_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock) -- cgit v1.2.3