| From fd533e0dc71bba293f47bd539a88b1ab550e69ae Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Fri, 22 May 2020 12:18:44 +0800 |
| Subject: ext4: fix partial cluster initialization when splitting extent |
| |
| From: Jeffle Xu <jefflexu@linux.alibaba.com> |
| |
| [ Upstream commit cfb3c85a600c6aa25a2581b3c1c4db3460f14e46 ] |
| |
| Fix the bug when calculating the physical block number of the first |
| block in the split extent. |
| |
| This bug will cause xfstests shared/298 failure on ext4 with bigalloc |
| enabled occasionally. Ext4 error messages indicate that previously freed |
| blocks are being freed again, and the following fsck will fail due to |
| the inconsistency of block bitmap and bg descriptor. |
| |
| The following is an example case: |
| |
| 1. First, Initialize a ext4 filesystem with cluster size '16K', block size |
| '4K', in which case, one cluster contains four blocks. |
| |
| 2. Create one file (e.g., xxx.img) on this ext4 filesystem. Now the extent |
| tree of this file is like: |
| |
| ... |
| 36864:[0]4:220160 |
| 36868:[0]14332:145408 |
| 51200:[0]2:231424 |
| ... |
| |
| 3. Then execute PUNCH_HOLE fallocate on this file. The hole range is |
| like: |
| |
| .. |
| ext4_ext_remove_space: dev 254,16 ino 12 since 49506 end 49506 depth 1 |
| ext4_ext_remove_space: dev 254,16 ino 12 since 49544 end 49546 depth 1 |
| ext4_ext_remove_space: dev 254,16 ino 12 since 49605 end 49607 depth 1 |
| ... |
| |
| 4. Then the extent tree of this file after punching is like |
| |
| ... |
| 49507:[0]37:158047 |
| 49547:[0]58:158087 |
| ... |
| |
| 5. Detailed procedure of punching hole [49544, 49546] |
| |
| 5.1. The block address space: |
| ``` |
| lblk ~49505 49506 49507~49543 49544~49546 49547~ |
| ---------+------+-------------+----------------+-------- |
| extent | hole | extent | hole | extent |
| ---------+------+-------------+----------------+-------- |
| pblk ~158045 158046 158047~158083 158084~158086 158087~ |
| ``` |
| |
| 5.2. The detailed layout of cluster 39521: |
| ``` |
| cluster 39521 |
| <-------------------------------> |
| |
| hole extent |
| <----------------------><-------- |
| |
| lblk 49544 49545 49546 49547 |
| +-------+-------+-------+-------+ |
| | | | | | |
| +-------+-------+-------+-------+ |
| pblk 158084 1580845 158086 158087 |
| ``` |
| |
| 5.3. The ftrace output when punching hole [49544, 49546]: |
| - ext4_ext_remove_space (start 49544, end 49546) |
| - ext4_ext_rm_leaf (start 49544, end 49546, last_extent [49507(158047), 40], partial [pclu 39522 lblk 0 state 2]) |
| - ext4_remove_blocks (extent [49507(158047), 40], from 49544 to 49546, partial [pclu 39522 lblk 0 state 2] |
| - ext4_free_blocks: (block 158084 count 4) |
| - ext4_mballoc_free (extent 1/6753/1) |
| |
| 5.4. Ext4 error message in dmesg: |
| EXT4-fs error (device vdb): mb_free_blocks:1457: group 1, block 158084:freeing already freed block (bit 6753); block bitmap corrupt. |
| EXT4-fs error (device vdb): ext4_mb_generate_buddy:747: group 1, block bitmap and bg descriptor inconsistent: 19550 vs 19551 free clusters |
| |
| In this case, the whole cluster 39521 is freed mistakenly when freeing |
| pblock 158084~158086 (i.e., the first three blocks of this cluster), |
| although pblock 158087 (the last remaining block of this cluster) has |
| not been freed yet. |
| |
| The root cause of this isuue is that, the pclu of the partial cluster is |
| calculated mistakenly in ext4_ext_remove_space(). The correct |
| partial_cluster.pclu (i.e., the cluster number of the first block in the |
| next extent, that is, lblock 49597 (pblock 158086)) should be 39521 rather |
| than 39522. |
| |
| Fixes: f4226d9ea400 ("ext4: fix partial cluster initialization") |
| Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com> |
| Reviewed-by: Eric Whitney <enwlinux@gmail.com> |
| Cc: stable@kernel.org # v3.19+ |
| Link: https://lore.kernel.org/r/1590121124-37096-1-git-send-email-jefflexu@linux.alibaba.com |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| fs/ext4/extents.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c |
| index 96336830f0350..fc2746e14c42a 100644 |
| --- a/fs/ext4/extents.c |
| +++ b/fs/ext4/extents.c |
| @@ -2902,7 +2902,7 @@ int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start, |
| * in use to avoid freeing it when removing blocks. |
| */ |
| if (sbi->s_cluster_ratio > 1) { |
| - pblk = ext4_ext_pblock(ex) + end - ee_block + 2; |
| + pblk = ext4_ext_pblock(ex) + end - ee_block + 1; |
| partial_cluster = |
| -(long long) EXT4_B2C(sbi, pblk); |
| } |
| -- |
| 2.25.1 |
| |
