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

[Huang Jianan]

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.

Thanks,
Jianan
> Thanks,
> Gao Xiang
>