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Commit 43c32bf2 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
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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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 3e2e1c30

drivers/md/dm-cache-target.c

+4 −2
Original line number Diff line number Diff line
@@ -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);