Re: [RFC PATCH] xfs: use log_incompat feature instead of speculate matching

Darrick J. Wong
2020-08-24T15:09:09Z

On Mon, Aug 24, 2020 at 04:34:02PM +0800, Gao Xiang wrote:
> On Mon, Aug 24, 2020 at 04:19:00PM +0800, Gao Xiang wrote:
> > From: Gao Xiang <hsiangkao@redhat.com>
> >
> > Use a log_incompat feature just to be safe.
> > If the current mount is in RO state, it will defer
> > to next RW remount.
> >
> > Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> > ---
> >
> > After some careful thinking, I think it's probably not working for
> > supported V4 XFS filesystem. So, I think we'd probably insist on the
> > previous way (correct me if I'm wrong)...
> >
> > (since xfs_sb_to_disk() refuses to set up any feature bits for non V5
> > fses. That is another awkward setting here (doesn't write out/check
> > feature bits for V4 even though using V4 sb reserved fields) and
> > unless let V4 completely RO since this commit. )
> >
> > Just send out as a RFC patch. Not fully tested after I thought as above.
>
> Unless we also use sb_features2 for V4 filesystem to entirely
> refuse to mount such V4 filesystem...
> Some more opinions on this?

Frankly, V4 is pretty old, so I wouldn't bother. We only build new
features for V5 format.

--D

> Thanks,
> Gao Xiang
>