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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
This commit is contained in:
Joe Thornber 2015-02-27 14:09:12 +00:00 committed by Mike Snitzer
parent c517d838eb
commit 5f027a3bf1
1 changed files with 0 additions and 11 deletions
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11
drivers/md/dm-thin.c
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@ -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;