src/patches/suse-2.6.27.31/patches.fixes/ext4-fix-sub-block-zeroing-for-preallocated-writes

   1 From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
   2 Date: Wed, 13 May 2009 22:36:58 +0000 (-0400)
   3 Subject: ext4: Fix sub-block zeroing for writes into preallocated extents
   4 Patch-mainline: 2.6.30
   5 Git-commit: 9c1ee184a30394e54165fa4c15923cabd952c106
   6 References: bnc#503161
   7
   8 ext4: Fix sub-block zeroing for writes into preallocated extents
   9
  10 We need to mark the buffer_head mapping preallocated space as new
  11 during write_begin. Otherwise we don't zero out the page cache content
  12 properly for a partial write. This will cause file corruption with
  13 preallocation.
  14
  15 Now that we mark the buffer_head new we also need to have a valid
  16 buffer_head blocknr so that unmap_underlying_metadata() unmaps the
  17 correct block.
  18
  19 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  20 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  21 Acked-by: Jeff Mahoney <jeffm@suse.com>
  22 ---
  23
  24  fs/ext4/extents.c |    2 ++
  25  fs/ext4/inode.c   |    7 +++++++
  26  2 files changed, 9 insertions(+)
  27
  28 --- a/fs/ext4/extents.c
  29 +++ b/fs/ext4/extents.c
  30 @@ -2664,6 +2664,8 @@ int ext4_ext_get_blocks(handle_t *handle
  31                                 if (allocated > max_blocks)
  32                                         allocated = max_blocks;
  33                                 set_buffer_unwritten(bh_result);
  34 +                               bh_result->b_bdev = inode->i_sb->s_bdev;
  35 +                               bh_result->b_blocknr = newblock;
  36                                 goto out2;
  37                         }
  38
  39 --- a/fs/ext4/inode.c
  40 +++ b/fs/ext4/inode.c
  41 @@ -2220,6 +2220,13 @@ static int ext4_da_get_block_prep(struct
  42                 set_buffer_delay(bh_result);
  43         } else if (ret > 0) {
  44                 bh_result->b_size = (ret << inode->i_blkbits);
  45 +               /*
  46 +                * With sub-block writes into unwritten extents
  47 +                * we also need to mark the buffer as new so that
  48 +                * the unwritten parts of the buffer gets correctly zeroed.
  49 +                */
  50 +               if (buffer_unwritten(bh_result))
  51 +                       set_buffer_new(bh_result);
  52                 ret = 0;
  53         }
  54