[PATCH 4.9 20/29] ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed

Greg Kroah-Hartman
2021-06-08T18:30:42Z

From: Ye Bin <yebin10@huawei.com>

commit 082cd4ec240b8734a82a89ffb890216ac98fec68 upstream.

We got follow bug_on when run fsstress with injecting IO fault:
[130747.323114] kernel BUG at fs/ext4/extents_status.c:762!
[130747.323117] Internal error: Oops - BUG: 0 [#1] SMP
......
[130747.334329] Call trace:
[130747.334553] ext4_es_cache_extent+0x150/0x168 [ext4]
[130747.334975] ext4_cache_extents+0x64/0xe8 [ext4]
[130747.335368] ext4_find_extent+0x300/0x330 [ext4]
[130747.335759] ext4_ext_map_blocks+0x74/0x1178 [ext4]
[130747.336179] ext4_map_blocks+0x2f4/0x5f0 [ext4]
[130747.336567] ext4_mpage_readpages+0x4a8/0x7a8 [ext4]
[130747.336995] ext4_readpage+0x54/0x100 [ext4]
[130747.337359] generic_file_buffered_read+0x410/0xae8
[130747.337767] generic_file_read_iter+0x114/0x190
[130747.338152] ext4_file_read_iter+0x5c/0x140 [ext4]
[130747.338556] __vfs_read+0x11c/0x188
[130747.338851] vfs_read+0x94/0x150
[130747.339110] ksys_read+0x74/0xf0

This patch's modification is according to Jan Kara's suggestion in:
https://patchwork.ozlabs.org/project/linux-ext4/patch/20210428085158.3728201-1-yebin10@huawei.com/
"I see. Now I understand your patch. Honestly, seeing how fragile is trying
to fix extent tree after split has failed in the middle, I would probably
go even further and make sure we fix the tree properly in case of ENOSPC
and EDQUOT (those are easily user triggerable). Anything else indicates a
HW problem or fs corruption so I'd rather leave the extent tree as is and
don't try to fix it (which also means we will not create overlapping
extents)."

Cc: stable@kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210506141042.3298679-1-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/extents.c | 43 +++++++++++++++++++++++--------------------
1 file changed, 23 insertions(+), 20 deletions(-)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3274,7 +3274,10 @@ static int ext4_split_extent_at(handle_t
ext4_ext_mark_unwritten(ex2);

err = ext4_ext_insert_extent(handle, inode, ppath, &newex, flags);
- if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
+ if (err != -ENOSPC && err != -EDQUOT)
+ goto out;
+
+ if (EXT4_EXT_MAY_ZEROOUT & split_flag) {
if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
if (split_flag & EXT4_EXT_DATA_VALID1) {
err = ext4_ext_zeroout(inode, ex2);
@@ -3300,30 +3303,30 @@ static int ext4_split_extent_at(handle_t
ext4_ext_pblock(&orig_ex));
}

- if (err)
- goto fix_extent_len;
- /* update the extent length and mark as initialized */
- ex->ee_len = cpu_to_le16(ee_len);
- ext4_ext_try_to_merge(handle, inode, path, ex);
- err = ext4_ext_dirty(handle, inode, path + path->p_depth);
- if (err)
- goto fix_extent_len;
-
- /* update extent status tree */
- err = ext4_zeroout_es(inode, &zero_ex);
-
- goto out;
- } else if (err)
- goto fix_extent_len;
-
-out:
- ext4_ext_show_leaf(inode, path);
- return err;
+ if (!err) {
+ /* update the extent length and mark as initialized */
+ ex->ee_len = cpu_to_le16(ee_len);
+ ext4_ext_try_to_merge(handle, inode, path, ex);
+ err = ext4_ext_dirty(handle, inode, path + path->p_depth);
+ if (!err)
+ /* update extent status tree */
+ err = ext4_zeroout_es(inode, &zero_ex);
+ /* If we failed at this point, we don't know in which
+ * state the extent tree exactly is so don't try to fix
+ * length of the original extent as it may do even more
+ * damage.
+ */
+ goto out;
+ }
+ }

fix_extent_len:
ex->ee_len = orig_ex.ee_len;
ext4_ext_dirty(handle, inode, path + path->p_depth);
return err;
+out:
+ ext4_ext_show_leaf(inode, path);
+ return err;
}

/*