releases/4.14.69/dm-cache-metadata-save-in-core-policy_hint_size-to-on-disk-superblock.patch

   1 From fd2fa95416188a767a63979296fa3e169a9ef5ec Mon Sep 17 00:00:00 2001
   2 From: Mike Snitzer <snitzer@redhat.com>
   3 Date: Thu, 2 Aug 2018 16:08:52 -0400
   4 Subject: dm cache metadata: save in-core policy_hint_size to on-disk superblock
   5
   6 From: Mike Snitzer <snitzer@redhat.com>
   7
   8 commit fd2fa95416188a767a63979296fa3e169a9ef5ec upstream.
   9
  10 policy_hint_size starts as 0 during __write_initial_superblock().  It
  11 isn't until the policy is loaded that policy_hint_size is set in-core
  12 (cmd->policy_hint_size).  But it never got recorded in the on-disk
  13 superblock because __commit_transaction() didn't deal with transfering
  14 the in-core cmd->policy_hint_size to the on-disk superblock.
  15
  16 The in-core cmd->policy_hint_size gets initialized by metadata_open()'s
  17 __begin_transaction_flags() which re-reads all superblock fields.
  18 Because the superblock's policy_hint_size was never properly stored, when
  19 the cache was created, hints_array_available() would always return false
  20 when re-activating a previously created cache.  This means
  21 __load_mappings() always considered the hints invalid and never made use
  22 of the hints (these hints served to optimize).
  23
  24 Another detremental side-effect of this oversight is the cache_check
  25 utility would fail with: "invalid hint width: 0"
  26
  27 Cc: stable@vger.kernel.org
  28 Signed-off-by: Mike Snitzer <snitzer@redhat.com>
  29 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  30
  31 ---
  32  drivers/md/dm-cache-metadata.c |    3 ++-
  33  1 file changed, 2 insertions(+), 1 deletion(-)
  34
  35 --- a/drivers/md/dm-cache-metadata.c
  36 +++ b/drivers/md/dm-cache-metadata.c
  37 @@ -362,7 +362,7 @@ static int __write_initial_superblock(st
  38         disk_super->version = cpu_to_le32(cmd->version);
  39         memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name));
  40         memset(disk_super->policy_version, 0, sizeof(disk_super->policy_version));
  41 -       disk_super->policy_hint_size = 0;
  42 +       disk_super->policy_hint_size = cpu_to_le32(0);
  43
  44         __copy_sm_root(cmd, disk_super);
  45
  46 @@ -700,6 +700,7 @@ static int __commit_transaction(struct d
  47         disk_super->policy_version[0] = cpu_to_le32(cmd->policy_version[0]);
  48         disk_super->policy_version[1] = cpu_to_le32(cmd->policy_version[1]);
  49         disk_super->policy_version[2] = cpu_to_le32(cmd->policy_version[2]);
  50 +       disk_super->policy_hint_size = cpu_to_le32(cmd->policy_hint_size);
  51
  52         disk_super->read_hits = cpu_to_le32(cmd->stats.read_hits);
  53         disk_super->read_misses = cpu_to_le32(cmd->stats.read_misses);