[PATCH 3.13.y-ckt 090/156] dm thin: fix to consistently zero-fill reads to unprovisioned blocks

[Kamal Mostafa]

3.13.11-ckt19 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Thornber <ejt@xxxxxxxxxx>

commit 5f027a3bf184d1d36e68745f7cd3718a8b879cc0 upstream.

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@xxxxxxxxxx>
Signed-off-by: Joe Thornber <ejt@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 drivers/md/dm-thin.c | 11 -----------
 1 file changed, 11 deletions(-)

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index d2b3563..34b8f2c 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1553,17 +1553,6 @@ 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.  Just error it.
-			 */
-			bio_io_error(bio);
-			cell_defer_no_holder_no_free(tc, &cell1);
-			return DM_MAPIO_SUBMITTED;
-		}
-		/* fall through */
-
 	case -EWOULDBLOCK:
 		/*
 		 * In future, the failed dm_thin_find_block above could
-- 
1.9.1

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