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Commit 80ae49aa authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm cache: do not add migration to completed list before unhooking bio 



When completing an overwrite bio, in overwrite_endio(), the associated
migration should not be added to the 'completed_migrations' until the
bio's fields are restored with dm_unhook_bio().

Otherwise, do_worker() can race to process 'completed_migrations' before
dm_unhook_bio() -- so the bio's bi_end_io is incorrect.  This is
unlikely to cause any problems given the current code but should be
fixed on the basis of correctness.

Also, the cache's spinlock only needs to be held when manipulating the
'completed_migrations' list -- other changes don't need protection.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarJoe Thornber <ejt@redhat.com>
parent c6eda5e8

drivers/md/dm-cache-target.c

+4 −2
Original line number Original line Diff line number Diff line
@@ -1010,13 +1010,15 @@ static void overwrite_endio(struct bio *bio, int err) 
	struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);

	struct per_bio_data *pb = get_per_bio_data(bio, pb_data_size);

	unsigned long flags;

	unsigned long flags;





	dm_unhook_bio(&pb->hook_info, bio);



	if (err)

	if (err)

		mg->err = true;

		mg->err = true;





	mg->requeue_holder = false;



	spin_lock_irqsave(&cache->lock, flags);

	spin_lock_irqsave(&cache->lock, flags);

	list_add_tail(&mg->list, &cache->completed_migrations);

	list_add_tail(&mg->list, &cache->completed_migrations);

	dm_unhook_bio(&pb->hook_info, bio);

	mg->requeue_holder = false;

	spin_unlock_irqrestore(&cache->lock, flags);

	spin_unlock_irqrestore(&cache->lock, flags);





	wake_worker(cache);

	wake_worker(cache);