trim-allocation-requests-to-group-size

   1 ext4: trim allocation requests to group size
   2
   3 From: Jan Kara <jack@suse.cz>
   4
   5 If filesystem groups are artifically small (using parameter -g to
   6 mkfs.ext4), ext4_mb_normalize_request() can result in a request that is
   7 larger than a block group. Trim the request size to not confuse
   8 allocation code.
   9
  10 Reported-by: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
  11 Signed-off-by: Jan Kara <jack@suse.cz>
  12 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  13 Cc: stable@vger.kernel.org
  14 ---
  15  fs/ext4/mballoc.c | 7 +++++++
  16  1 file changed, 7 insertions(+)
  17
  18 diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
  19 index 7ae43c59bc79..2e9fc7a61048 100644
  20 --- a/fs/ext4/mballoc.c
  21 +++ b/fs/ext4/mballoc.c
  22 @@ -3123,6 +3123,13 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
  23         if (ar->pright && start + size - 1 >= ar->lright)
  24                 size -= start + size - ar->lright;
  25
  26 +       /*
  27 +        * Trim allocation request for filesystems with artificially small
  28 +        * groups.
  29 +        */
  30 +       if (size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb))
  31 +               size = EXT4_BLOCKS_PER_GROUP(ac->ac_sb);
  32 +
  33         end = start + size;
  34
  35         /* check we don't cross already preallocated blocks */
  36 --
  37 2.10.2
  38
  39