Re: [PATCH] ceph: fix mdsmap decode for v >= 17

[Xiubo Li]

On 28/10/2022 17:05, Luís Henriques wrote:
> On Fri, Oct 28, 2022 at 09:28:37AM +0800, Xiubo Li wrote:
> > On 27/10/2022 23:28, Luís Henriques wrote:
> > > Commit d93231a6bc8a ("ceph: prevent a client from exceeding the MDS
> > > maximum xattr size") was merged before the corresponding MDS-side changes
> > > have been merged.  With the introduction of 'bal_rank_mask' in the mdsmap,
> > > the decoding of maps with v>=17 is now incorrect.  Fix this by skipping
> > > the 'bal_rank_mask' string decoding.
> > >
> > > Fixes: d93231a6bc8a ("ceph: prevent a client from exceeding the MDS maximum xattr size")
> > > Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
> > > ---
> > > Hi!
> > >
> > > This inconsistency was introduced by ceph PR #43284; I think that, before
> > > picking this patch, we need to get PR #46357 merged to avoid new
> > > problems.
> > >
> > > Cheers,
> > > --
> > > Luís
> > >
> > >    fs/ceph/mdsmap.c | 2 ++
> > >    1 file changed, 2 insertions(+)
> > >
> > > diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
> > > index 3fbabc98e1f7..fe4f1a6c3465 100644
> > > --- a/fs/ceph/mdsmap.c
> > > +++ b/fs/ceph/mdsmap.c
> > > @@ -379,6 +379,8 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
> > >    		ceph_decode_skip_8(p, end, bad_ext);
> > >    		/* required_client_features */
> > >    		ceph_decode_skip_set(p, end, 64, bad_ext);
> > > +		/* bal_rank_mask */
> > > +		ceph_decode_skip_string(p, end, bad_ext);
> > >    		ceph_decode_64_safe(p, end, m->m_max_xattr_size, bad_ext);
> > >    	} else {
> > >    		/* This forces the usage of the (sync) SETXATTR Op */
> > Luis,
> >
> > Because the ceph PR #43284 will break kclient here and your xattr size patch
> > got merged long time ago, we should fix it in ceph. More detail please see
> > my comments in:
> >
> > https://github.com/ceph/ceph/pull/46357#issuecomment-1294290492
> OK, agreed.  I'll update this PR to try to fix it on the MDS side
> instead.  And let's try to have it merged as soon as possible to prevent
> further issues.

Sounds good!

- Xiubo


> Cheers,
> --
> Luís