Re: [PATCH v3] ext4: fix bug for rename with RENAME_WHITEOUT

Theodore Ts'o
2021-01-14T03:53:03Z

On Tue, Jan 05, 2021 at 02:28:57PM +0800, yangerkun wrote:
> We got a "deleted inode referenced" warning cross our fsstress test. The
> bug can be reproduced easily with following steps:
>
> cd /dev/shm
> mkdir test/
> fallocate -l 128M img
> mkfs.ext4 -b 1024 img
> mount img test/
> dd if=/dev/zero of=test/foo bs=1M count=128
> mkdir test/dir/ && cd test/dir/
> for ((i=0;i<1000;i++)); do touch file$i; done # consume all block
> cd ~ && renameat2(AT_FDCWD, /dev/shm/test/dir/file1, AT_FDCWD,
> /dev/shm/test/dir/dst_file, RENAME_WHITEOUT) # ext4_add_entry in
> ext4_rename will return ENOSPC!!
> cd /dev/shm/ && umount test/ && mount img test/ && ls -li test/dir/file1
> We will get the output:
> "ls: cannot access 'test/dir/file1': Structure needs cleaning"
> and the dmesg show:
> "EXT4-fs error (device loop0): ext4_lookup:1626: inode #2049: comm ls:
> deleted inode referenced: 139"
>
> ext4_rename will create a special inode for whiteout and use this 'ino'
> to replace the source file's dir entry 'ino'. Once error happens
> latter(the error above was the ENOSPC return from ext4_add_entry in
> ext4_rename since all space has been consumed), the cleanup do drop the
> nlink for whiteout, but forget to restore 'ino' with source file. This
> will trigger the bug describle as above.
>
> Signed-off-by: yangerkun <yangerkun@huawei.com>

Thanks, replied.

- Ted