Commit 962e8a01eab9 ("ext4: introduce mext_move_extent()") attempts to call ext4_swap_extents() on the failure path to recover the swapped extents, but fails to acquire locks for the two inode->i_data_sem, triggering the BUG_ON statement in ext4_swap_extents(). This issue can be fixed by calling ext4_double_down_write_data_sem() before ext4_swap_extents(). Signed-off-by: Julian Sun Reported-by: syzbot+4ea6bd8737669b423aae@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69368649.a70a0220.38f243.0093.GAE@google.com/ Fixes: 962e8a01eab9 ("ext4: introduce mext_move_extent()") --- fs/ext4/move_extent.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c index 0550fd30fd10..635fb8a52e0c 100644 --- a/fs/ext4/move_extent.c +++ b/fs/ext4/move_extent.c @@ -393,9 +393,11 @@ static int mext_move_extent(struct mext_data *mext, u64 *m_len) repair_branches: ret2 = 0; + ext4_double_down_write_data_sem(orig_inode, donor_inode); r_len = ext4_swap_extents(handle, donor_inode, orig_inode, mext->donor_lblk, orig_map->m_lblk, *m_len, 0, &ret2); + ext4_double_up_write_data_sem(orig_inode, donor_inode); if (ret2 || r_len != *m_len) { ext4_error_inode_block(orig_inode, (sector_t)(orig_map->m_lblk), EIO, "Unable to copy data block, data will be lost!"); -- 2.39.5