From: Joe Thornber Date: Tue, 25 Nov 2014 13:14:57 +0000 (+0000) Subject: dm cache: fix a harmless race when working out if a block is discarded X-Git-Tag: v3.19-rc1~177^2~8 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=43c32bf2b0c16d292f4f214dfd16f9cb205e4e81;p=linux.git dm cache: fix a harmless race when working out if a block is discarded It is more correct to hold the cell before checking the discard state. These flags are only used as hints to the policy so this change will have negligable effect. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer --- diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 2c66315553f2..161bbd6652f8 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1432,9 +1432,8 @@ static void process_bio(struct cache *cache, struct prealloc *structs, dm_oblock_t block = get_bio_block(cache, bio); struct dm_bio_prison_cell *cell_prealloc, *old_ocell, *new_ocell; struct policy_result lookup_result; - bool discarded_block = is_discarded_oblock(cache, block); bool passthrough = passthrough_mode(&cache->features); - bool can_migrate = !passthrough && (discarded_block || spare_migration_bandwidth(cache)); + bool discarded_block, can_migrate; /* * Check to see if that block is currently migrating. @@ -1446,6 +1445,9 @@ static void process_bio(struct cache *cache, struct prealloc *structs, if (r > 0) return; + discarded_block = is_discarded_oblock(cache, block); + can_migrate = !passthrough && (discarded_block || spare_migration_bandwidth(cache)); + r = policy_map(cache->policy, block, true, can_migrate, discarded_block, bio, &lookup_result);