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Commit 8974fec7 authored by Eryu Guan's avatar Eryu Guan Committed by Theodore Ts'o
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ext4: correctly migrate a file with a hole at the beginning 



Currently ext4_ind_migrate() doesn't correctly handle a file which
contains a hole at the beginning of the file.  This caused the migration
to be done incorrectly, and then if there is a subsequent following
delayed allocation write to the "hole", this would reclaim the same data
blocks again and results in fs corruption.

  # assmuing 4k block size ext4, with delalloc enabled
  # skip the first block and write to the second block
  xfs_io -fc "pwrite 4k 4k" -c "fsync" /mnt/ext4/testfile

  # converting to indirect-mapped file, which would move the data blocks
  # to the beginning of the file, but extent status cache still marks
  # that region as a hole
  chattr -e /mnt/ext4/testfile

  # delayed allocation writes to the "hole", reclaim the same data block
  # again, results in i_blocks corruption
  xfs_io -c "pwrite 0 4k" /mnt/ext4/testfile
  umount /mnt/ext4
  e2fsck -nf /dev/sda6
  ...
  Inode 53, i_blocks is 16, should be 8.  Fix? no
  ...

Signed-off-by: default avatarEryu Guan <guaneryu@gmail.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
parent d6f123a9

fs/ext4/migrate.c

+5 −4
Original line number Diff line number Diff line
@@ -620,7 +620,7 @@ int ext4_ind_migrate(struct inode *inode) 
	struct ext4_inode_info		*ei = EXT4_I(inode);

	struct ext4_extent		*ex;

	unsigned int			i, len;

	ext4_lblk_t			end;

	ext4_lblk_t			start, end;

	ext4_fsblk_t			blk;

	handle_t			*handle;

	int				ret;
@@ -659,11 +659,12 @@ int ext4_ind_migrate(struct inode *inode) 
		goto errout;

	}

	if (eh->eh_entries == 0)

		blk = len = 0;

		blk = len = start = end = 0;

	else {

		len = le16_to_cpu(ex->ee_len);

		blk = ext4_ext_pblock(ex);

		end = le32_to_cpu(ex->ee_block) + len - 1;

		start = le32_to_cpu(ex->ee_block);

		end = start + len - 1;

		if (end >= EXT4_NDIR_BLOCKS) {

			ret = -EOPNOTSUPP;

			goto errout;
@@ -672,7 +673,7 @@ int ext4_ind_migrate(struct inode *inode) 


	ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);

	memset(ei->i_data, 0, sizeof(ei->i_data));

	for (i=0; i < len; i++)

	for (i = start; i <= end; i++)

		ei->i_data[i] = cpu_to_le32(blk++);

	ext4_mark_inode_dirty(handle, inode);

errout: