block-dio-during-truncate

   1 ext4: block direct I/O writes during ext4_truncate
   2
   3 Just as in ext4_punch_hole() it is important that we block DIO writes
   4 while the truncate is proceeding, since during the overwriting DIO
   5 write, we drop i_mutex, which means a truncate could start while the
   6 Direct I/O operation is still in progress.
   7
   8 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
   9 Cc: stable@vger.kernel.org
  10 ---
  11  fs/ext4/inode.c | 10 ++++++++--
  12  1 file changed, 8 insertions(+), 2 deletions(-)
  13
  14 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  15 index 98b9bff..3c5edf2 100644
  16 --- a/fs/ext4/inode.c
  17 +++ b/fs/ext4/inode.c
  18 @@ -3659,12 +3659,16 @@ void ext4_truncate(struct inode *inode)
  19         if (inode->i_size == 0 && !test_opt(inode->i_sb, NO_AUTO_DA_ALLOC))
  20                 ext4_set_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
  21
  22 +       /* Wait all existing dio workers, newcomers will block on i_mutex */
  23 +       ext4_inode_block_unlocked_dio(inode);
  24 +       inode_dio_wait(inode);
  25 +
  26         if (ext4_has_inline_data(inode)) {
  27                 int has_inline = 1;
  28
  29                 ext4_inline_data_truncate(inode, &has_inline);
  30                 if (has_inline)
  31 -                       return;
  32 +                       goto out_resume;
  33         }
  34
  35         if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  36 @@ -3675,7 +3679,7 @@ void ext4_truncate(struct inode *inode)
  37         handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
  38         if (IS_ERR(handle)) {
  39                 ext4_std_error(inode->i_sb, PTR_ERR(handle));
  40 -               return;
  41 +               goto out_resume;
  42         }
  43
  44         if (inode->i_size & (inode->i_sb->s_blocksize - 1))
  45 @@ -3722,6 +3726,8 @@ out_stop:
  46         ext4_mark_inode_dirty(handle, inode);
  47         ext4_journal_stop(handle);
  48
  49 +out_resume:
  50 +       ext4_inode_resume_unlocked_dio(inode);
  51         trace_ext4_truncate_exit(inode);
  52  }
  53