ext4: fix fs corruption when tring to remove a non-empty directory with IO error

ext4: fix fs corruption when tring to remove a non-empty directory with IO error

We inject IO error when rmdir non empty direcory, then got issue as follows:
step1: mkfs.ext4 -F /dev/sda
step2: mount /dev/sda  test
step3: cd test
step4: mkdir -p 1/2
step5: rmdir 1
	[  110.920551] ext4_empty_dir: inject fault
	[  110.921926] EXT4-fs warning (device sda): ext4_rmdir:3113: inode #12:
	comm rmdir: empty directory '1' has too many links (3)
step6: cd ..
step7: umount test
step8: fsck.ext4 -f /dev/sda
	e2fsck 1.42.9 (28-Dec-2013)
	Pass 1: Checking inodes, blocks, and sizes
	Pass 2: Checking directory structure
	Entry '..' in .../??? (13) has deleted/unused inode 12.  Clear<y>? yes
	Pass 3: Checking directory connectivity
	Unconnected directory inode 13 (...)
	Connect to /lost+found<y>? yes
	Pass 4: Checking reference counts
	Inode 13 ref count is 3, should be 2.  Fix<y>? yes
	Pass 5: Checking group summary information

	/dev/sda: ***** FILE SYSTEM WAS MODIFIED *****
	/dev/sda: 12/131072 files (0.0% non-contiguous), 26157/524288 blocks

ext4_rmdir
	if (!ext4_empty_dir(inode))
		goto end_rmdir;
ext4_empty_dir
	bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
	if (IS_ERR(bh))
		return true;
Now if read directory block failed, 'ext4_empty_dir' will return true, assume
directory is empty. Obviously, it will lead to above issue.
To solve this issue, if read directory block failed 'ext4_empty_dir' just
return false. To avoid making things worse when file system is already
corrupted, 'ext4_empty_dir' also return false.

Signed-off-by: Ye Bin <yebin10@huawei.com>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20220228024815.3952506-1-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>