releases/3.19.4/dm-thin-fix-to-consistently-zero-fill-reads-to-unprovisioned-blocks.patch

   1 From 5f027a3bf184d1d36e68745f7cd3718a8b879cc0 Mon Sep 17 00:00:00 2001
   2 From: Joe Thornber <ejt@redhat.com>
   3 Date: Fri, 27 Feb 2015 14:09:12 +0000
   4 Subject: dm thin: fix to consistently zero-fill reads to unprovisioned blocks
   5
   6 From: Joe Thornber <ejt@redhat.com>
   7
   8 commit 5f027a3bf184d1d36e68745f7cd3718a8b879cc0 upstream.
   9
  10 It was always intended that a read to an unprovisioned block will return
  11 zeroes regardless of whether the pool is in read-only or read-write
  12 mode.  thin_bio_map() was inconsistent with its handling of such reads
  13 when the pool is in read-only mode, it now properly zero-fills the bios
  14 it returns in response to unprovisioned block reads.
  15
  16 Eliminate thin_bio_map()'s special read-only mode handling of -ENODATA
  17 and just allow the IO to be deferred to the worker which will result in
  18 pool->process_bio() handling the IO (which already properly zero-fills
  19 reads to unprovisioned blocks).
  20
  21 Reported-by: Eric Sandeen <sandeen@redhat.com>
  22 Signed-off-by: Joe Thornber <ejt@redhat.com>
  23 Signed-off-by: Mike Snitzer <snitzer@redhat.com>
  24 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  25
  26 ---
  27  drivers/md/dm-thin.c |   11 -----------
  28  1 file changed, 11 deletions(-)
  29
  30 --- a/drivers/md/dm-thin.c
  31 +++ b/drivers/md/dm-thin.c
  32 @@ -2357,17 +2357,6 @@ static int thin_bio_map(struct dm_target
  33                 return DM_MAPIO_REMAPPED;
  34
  35         case -ENODATA:
  36 -               if (get_pool_mode(tc->pool) == PM_READ_ONLY) {
  37 -                       /*
  38 -                        * This block isn't provisioned, and we have no way
  39 -                        * of doing so.
  40 -                        */
  41 -                       handle_unserviceable_bio(tc->pool, bio);
  42 -                       cell_defer_no_holder(tc, virt_cell);
  43 -                       return DM_MAPIO_SUBMITTED;
  44 -               }
  45 -               /* fall through */
  46 -
  47         case -EWOULDBLOCK:
  48                 thin_defer_cell(tc, virt_cell);
  49                 return DM_MAPIO_SUBMITTED;