Commit e33bafad authored May 06, 2021 by Ye Bin Committed by Greg Kroah-Hartman Jun 10, 2021

ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed

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>

parent 400d3eff

fs/ext4/extents.c

+23 −20

Original line number	Diff line number	Diff line
		@@ -3268,7 +3268,10 @@ static int ext4_split_extent_at(handle_t *handle,
		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);
		@@ -3294,30 +3297,30 @@ static int ext4_split_extent_at(handle_t *handle,
		ext4_ext_pblock(&orig_ex));
		}

		if (err)
		goto fix_extent_len;
		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)
		goto fix_extent_len;

		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;
		} else if (err)
		goto fix_extent_len;

		out:
		ext4_ext_show_leaf(inode, path);
		return err;
		}
		}

		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;
		}

		/*