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

["Theodore Ts'o" <tytso@mit.edu>]

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