Re: [PATCH AUTOSEL 5.14 46/99] ovl: copy up sync/noatime fileattr flags

[Sasha Levin]

On Fri, Sep 10, 2021 at 08:35:41AM +0300, Amir Goldstein wrote:
> On Fri, Sep 10, 2021 at 3:17 AM Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Amir Goldstein <amir73il@xxxxxxxxx>
> >
> > [ Upstream commit 72db82115d2bdfbfba8b15a92d91872cfe1b40c6 ]
> >
> > When a lower file has sync/noatime fileattr flags, the behavior of
> > overlayfs post copy up is inconsistent.
> >
> > Immediately after copy up, ovl inode still has the S_SYNC/S_NOATIME
> > inode flags copied from lower inode, so vfs code still treats the ovl
> > inode as sync/noatime.  After ovl inode evict or mount cycle,
> > the ovl inode does not have these inode flags anymore.
> >
> > To fix this inconsistency, try to copy the fileattr flags on copy up
> > if the upper fs supports the fileattr_set() method.
> >
> > This gives consistent behavior post copy up regardless of inode eviction
> > from cache.
> >
> > We cannot copy up the immutable/append-only inode flags in a similar
> > manner, because immutable/append-only inodes cannot be linked and because
> > overlayfs will not be able to set overlay.* xattr on the upper inodes.
> >
> > Those flags will be addressed by a followup patch.
> >
> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> > Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> > ---
>
> Sasha,
>
> I do not recommend applying this patch to stable.
> The value/risk ratio is not worth it IMO.
>
> I don't know of anyone who ever complained about not copying
> the NOATIME/SYNC fileattrs specifically.
>
> This patch is more of a complimentary patch to the IMMUTABLE/
> APPEND fileattr patch, which is not appropriate for stable either.

Thanks! I'll drop it.

> OTOH, ovl-update-5.15 has this patch that was not included in the
> AUTOSEL batch, even though it has a Fixes tag, CC stable and
> very strong hints in the subject:
> 52d5a0c6bd8a ("ovl: fix BUG_ON() in may_delete() when called from
> ovl_cleanup()")
>
> I suppose AUTOSEL leaves these sorts of patches to Greg's scripts?

That's correct. If it has a stable tag AUTOSEL won't look at it (why
should it? :) ).

--
Thanks,
Sasha