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Commit c822ed96 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm thin: grab a virtual cell before looking up the mapping 



Avoids normal IO racing with discard.

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
parent d20c4b08

drivers/md/dm-thin.c

+12 −4
Original line number Diff line number Diff line
@@ -1936,6 +1936,14 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
		return DM_MAPIO_SUBMITTED;

	}



	/*

	 * We must hold the virtual cell before doing the lookup, otherwise

	 * there's a race with discard.

	 */

	build_virtual_key(tc->td, block, &key);

	if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))

		return DM_MAPIO_SUBMITTED;



	r = dm_thin_find_block(td, block, 0, &result);



	/*
@@ -1959,13 +1967,10 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
			 * shared flag will be set in their case.

			 */

			thin_defer_bio(tc, bio);

			cell_defer_no_holder_no_free(tc, &cell1);

			return DM_MAPIO_SUBMITTED;

		}



		build_virtual_key(tc->td, block, &key);

		if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))

			return DM_MAPIO_SUBMITTED;



		build_data_key(tc->td, result.block, &key);

		if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) {

			cell_defer_no_holder_no_free(tc, &cell1);
@@ -1986,6 +1991,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
			 * of doing so.

			 */

			handle_unserviceable_bio(tc->pool, bio);

			cell_defer_no_holder_no_free(tc, &cell1);

			return DM_MAPIO_SUBMITTED;

		}

		/* fall through */
@@ -1996,6 +2002,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
		 * provide the hint to load the metadata into cache.

		 */

		thin_defer_bio(tc, bio);

		cell_defer_no_holder_no_free(tc, &cell1);

		return DM_MAPIO_SUBMITTED;



	default:
@@ -2005,6 +2012,7 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio) 
		 * pool is switched to fail-io mode.

		 */

		bio_io_error(bio);

		cell_defer_no_holder_no_free(tc, &cell1);

		return DM_MAPIO_SUBMITTED;

	}

}