Commit 5f027a3b authored Feb 27, 2015 by Joe Thornber Committed by Mike Snitzer Feb 27, 2015

dm thin: fix to consistently zero-fill reads to unprovisioned blocks



It was always intended that a read to an unprovisioned block will return
zeroes regardless of whether the pool is in read-only or read-write
mode.  thin_bio_map() was inconsistent with its handling of such reads
when the pool is in read-only mode, it now properly zero-fills the bios
it returns in response to unprovisioned block reads.

Eliminate thin_bio_map()'s special read-only mode handling of -ENODATA
and just allow the IO to be deferred to the worker which will result in
pool->process_bio() handling the IO (which already properly zero-fills
reads to unprovisioned blocks).

Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

parent c517d838

drivers/md/dm-thin.c

+0 −11

Original line number	Diff line number	Diff line
		@@ -2358,17 +2358,6 @@ static int thin_bio_map(struct dm_target ti, struct bio bio)
		return DM_MAPIO_REMAPPED;

		case -ENODATA:
		if (get_pool_mode(tc->pool) == PM_READ_ONLY) {
		/*
		* This block isn't provisioned, and we have no way
		* of doing so.
		*/
		handle_unserviceable_bio(tc->pool, bio);
		cell_defer_no_holder(tc, virt_cell);
		return DM_MAPIO_SUBMITTED;
		}
		/* fall through */

		case -EWOULDBLOCK:
		thin_defer_cell(tc, virt_cell);
		return DM_MAPIO_SUBMITTED;