[PATCH v2 1/2] erofs-utils: sort shared xattr

[Huang Jianan]

在 2021/12/15 11:22, Gao Xiang 写道:
> On Wed, Dec 15, 2021 at 10:43:40AM +0800, Huang Jianan via Linux-erofs wrote:
>> Hi Xiang,
>>
>> 在 2021/12/14 23:31, Gao Xiang 写道:
>>> Hi Jianan,
>>>
>>> On Tue, Dec 14, 2021 at 05:52:01PM +0800, Huang Jianan via Linux-erofs wrote:
>>>> Sort shared xattr before writing to disk to ensure the consistency
>>>> of reproducible builds.
>>>>
>>>> Signed-off-by: Huang Jianan <huangjianan at oppo.com>
>>> I still fail to understand why the order of shared xattrs will be
>>> a problem of reproducible builds.
>>>
>>> IOWs, if the order of shared xattrs is really a problem, do we need
>>> to sort inline xattrs as well? Or do you have some reproducer to
>>> show why the order of shared xattrs can be changed if the filesystem
>>> of srcdir isn't changed?
>> We discovered this problem when we built the same image content on
>> different machines.
>>
>> After executing readdir, the order of the subdirectories returned by the
>> two machines is different, which leads to a difference in the order of
>> shared
>> xattr. I'm not sure if this scene can be called reproducible build in the
>> strict
>> sense.
>>
>> In addition, since the problem is caused by the readdir sequence, it should
>> have no effect on inline xattr.
> So it sounds like we need to optimize xattr readdir process instead?
Agree, currently xattr will prepare before sorting the subdirectories , 
I will try
to put the process after sorting.

Thanks,
Jianan
> Thanks,
> Gao Xiang
>
>> Thanks,
>> Jianan
>>> Thanks,
>>> Gao Xiang
>>>