zero_range-fix-incorect-journal-credits-reservation

   1 ext4: fix incorect journal credits reservation in ext4_zero_range
   2
   3 From: Dmitry Monakhov <dmonakhov@openvz.org>
   4
   5 Currently we reserve only 4 blocks but in worst case scenario
   6 ext4_zero_partial_blocks() may want to zeroout and convert two
   7 non adjacent blocks.
   8
   9 Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
  10 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  11 Cc: stable@vger.kernel.org
  12 ---
  13  fs/ext4/extents.c |    6 ++++--
  14  1 files changed, 4 insertions(+), 2 deletions(-)
  15
  16 diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
  17 index 5bf718b..f09dbe7 100644
  18 --- a/fs/ext4/extents.c
  19 +++ b/fs/ext4/extents.c
  20 @@ -4740,6 +4740,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
  21         loff_t new_size = 0;
  22         int ret = 0;
  23         int flags;
  24 +       int credits;
  25         int partial;
  26         loff_t start, end;
  27         ext4_lblk_t lblk;
  28 @@ -4839,8 +4840,9 @@ static long ext4_zero_range(struct file *file, loff_t offset,
  29                 if (ret)
  30                         goto out_dio;
  31         }
  32 -
  33 -       handle = ext4_journal_start(inode, EXT4_HT_MISC, 4);
  34 +       /* In worst case we have to writeout two nonadjacent unwritten blocks */
  35 +       credits = ext4_ext_index_trans_blocks(inode, 2) + 2;
  36 +       handle = ext4_journal_start(inode, EXT4_HT_MISC, credits);
  37         if (IS_ERR(handle)) {
  38                 ret = PTR_ERR(handle);
  39                 ext4_std_error(inode->i_sb, ret);
  40 --
  41 1.7.1
  42