mkfs.erofs fails (failed to build shared xattrs, err 61)

[Gao Xiang]

On 2024/3/12 19:37, Gao Xiang wrote:
> 
> 
> On 2024/3/12 19:07, Gael Donval wrote:
>>> On 2024/3/12 18:44, Gao Xiang wrote:
>>>> Hi Gael,
>>>>
>>>> On 2024/3/12 17:57, Gael Donval wrote:
>>>>> Dear list,
>>>>>
>>>>>      $ mkdir foo && touch foo/bar && mkfs.erofs foo.erofs.img foo
>>>>>      mkfs.erofs 1.7.1
>>>>>      <E> erofs: failed to build shared xattrs: [Error 61] No data
>>>>> available
>>>>>      <E> erofs:     Could not format the device : [Error 61] No
>>>>> data available
>>>>> That is at a location backed by BTRFS (btrfs-progs v6.7.1) on
>>>>> kernel 6.8.0.
>>>>>
>>>>> If I use a TMPFS-supported folder instead all goes well.
>>>>>
>>>>>
>>>>> Of course (NB "-x-1"),
>>>>>
>>>>>      $ mkdir foo && touch foo/bar && mkfs.erofs -x-1 foo.erofs.img
>>>>> foo
>>>>>
>>>>> also works but is not how mkfs.erofs is meant to work in the
>>>>> general case.
>>>>
>>>> Thanks for your feedback.
>>>>
>>>> Currently I don't have some BTRFS environment, I could set up one
>>>> later.
>>>> Yet in parallel could you provide a full message of
>>>> "strace mkfs.erofs -x-1 foo.erofs.img foo" on BTRFS too?
>>>
>>> sorry, I meant "strace mkfs.erofs foo.erofs.img foo"
>>
>> Hi,
>>
>> Here it is.
>>
> 
> The problem here is that BTRFS could extract their internal
> xattrs ("inode properties") in their own namespace which
> don't belong to the original file itself like:
> 
> XATTR_BTRFS_PREFIX "compression" -> btrfs.compression = zstd
> 
> I think I need to introduce something to formally ignore
> these xattrs like: `--xattrs-exclude=pattern`:
> https://www.gnu.org/software/tar/manual/html_node/Extended-File-Attributes.html

BTW, as for erofs-utils 1.7.1, you may use
tar c --xattrs-exclude="btrfs.*" foo | mkfs.erofs --tar=f 111.erofs

as a workaround.  I think it will work.

Thanks,
Gao Xiang