In ext4_move_extents(), moved_len is only updated when all moves are successfully executed, and only discards orig_inode and donor_inode preallocations when moved_len is not zero. When the loop fails to exit after successfully moving some extents, moved_len is not updated and remains at 0, so it does not discard the preallocations. If the moved extents overlap with the preallocated extents, the overlapped extents are freed twice in ext4_mb_release_inode_pa() and ext4_process_freed_data() (as described in commit 94d7c16cbbbd), and bb_free is incremented twice. Hence when trim is executed, a zero-division bug is triggered in mb_update_avg_fragment_size() because bb_free is not zero and bb_fragments is zero. Therefore, update move_len after each extent move to avoid the issue. Reported-by: Wei Chen <harperchen1110@xxxxxxxxx> Reported-by: xingwei lee <xrivendell7@xxxxxxxxx> Closes: https://lore.kernel.org/r/CAO4mrferzqBUnCag8R3m2zf897ts9UEuhjFQGPtODT92rYyR2Q@xxxxxxxxxxxxxx Fixes: fcf6b1b729bc ("ext4: refactor ext4_move_extents code base") CC: stable@xxxxxxxxxxxxxxx # 3.18 Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx> --- fs/ext4/move_extent.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c index 3aa57376d9c2..4b9b503c6346 100644 --- a/fs/ext4/move_extent.c +++ b/fs/ext4/move_extent.c @@ -672,7 +672,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk, */ ext4_double_up_write_data_sem(orig_inode, donor_inode); /* Swap original branches with new branches */ - move_extent_per_page(o_filp, donor_inode, + *moved_len += move_extent_per_page(o_filp, donor_inode, orig_page_index, donor_page_index, offset_in_page, cur_len, unwritten, &ret); @@ -682,7 +682,6 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk, o_start += cur_len; d_start += cur_len; } - *moved_len = o_start - orig_blk; if (*moved_len > len) *moved_len = len; -- 2.31.1
