On Sun, Nov 10, 2024 at 01:05:33PM -0500, Theodore Ts'o wrote:
> The test generic/645 is failing on (at least) 6.6, 6.1, 5.15 LTS
> kernels.
>
> This fix is apparently commit dacfd001eaf2 ("fs/mnt_idmapping.c:
> Return -EINVAL when no map is written"), but in order to take this
> patch, it looks like we need to backport the 4 patch series
> "mnt_idmapping: decouple from namespaces"[1] (and possibly others; I
> haven't tried yet).
>
> [1] https://lore.kernel.org/all/20231122-vfs-mnt_idmap-v1-0-dae4abdde5bd@xxxxxxxxxx/
>
> This looks fairly involved so the questions I have are:
>
> (1) Should we request this patch series plus commit dacfd001eaf2 into
> the stable kernels --- or should I just add a versioned excludes[2]
> and just skip generic/645 from all kernels older than Linux 6.9 if we
> think it's too involved and/or risky to backport these id mapping
> changes?
>
> (2) How much do we care that generic/645 is failing on LTS kernels?
> Are user/applications going to notice or care?
No userspace used an empty idmapping and it was unclear whether the
behavior would be well-specified so the patch changed that quite some
time ago.
Backporting this to older LTS kernels isn't difficult. We just need
custom patches for the LTS kernels but they should all be very simple.
Alternatively, you can just ignore the test on older kernels.
