ext4: be more strict when migrating to non-extent based file
Currently the check in ext4_ind_migrate() is not enough before doing the
real conversion:
a) delayed allocated extents could bypass the check on eh->eh_entries
and eh->eh_depth
This can be demonstrated by this script
xfs_io -fc "pwrite 0 4k" -c "pwrite 8k 4k" /mnt/ext4/testfile
chattr -e /mnt/ext4/testfile
where testfile has two extents but still be converted to non-extent
based file format.
b) only extent length is checked but not the offset, which would result
in data lose (delalloc) or fs corruption (nodelalloc), because
non-extent based file only supports at most (12 + 2^10 + 2^20 + 2^30)
blocks
This can be demostrated by
xfs_io -fc "pwrite 5T 4k" /mnt/ext4/testfile
chattr -e /mnt/ext4/testfile
sync
If delalloc is enabled, dmesg prints
EXT4-fs warning (device dm-4): ext4_block_to_path:105: block 1342177280 > max in inode 53
EXT4-fs (dm-4): Delayed block allocation failed for inode 53 at logical offset 1342177280 with max blocks 1 with error 5
EXT4-fs (dm-4): This should not happen!! Data will be lost
If delalloc is disabled, e2fsck -nf shows corruption
Inode 53, i_size is 5497558142976, should be 4096. Fix? no
Fix the two issues by
a) forcing all delayed allocation blocks to be allocated before checking
eh->eh_depth and eh->eh_entries
b) limiting the last logical block of the extent is within direct map
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
1 file changed