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: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index 6d8b0c9..6163ad2 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -620,7 +620,7 @@
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 @@
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 @@
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: