RE: [PATCH] ceph: clear `s_cap_reconnect` when ceph_pagelist_encode_32() fails

[Viacheslav Dubeyko]

On Mon, 2026-03-30 at 17:29 +0000, Viacheslav Dubeyko wrote:
> On Mon, 2026-03-30 at 10:43 +0200, Max Kellermann wrote:
> > This MDS reconnect error path leaves s_cap_reconnect set.
> > send_mds_reconnect() sets the bit at the beginning of the reconnect,
> > but the first failing operation after that, ceph_pagelist_encode_32(),
> > can jump to `fail:` without clearing it.
> > 
> > __ceph_remove_cap() consults that flag to decide whether cap releases
> > should be queued. A reconnect-preparation failure therefore leaves the
> > session in reconnect mode from the cap-release path's point of view
> > and can strand release work until some later state transition repairs
> > it.
> > 
> > Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
> > ---
> >  fs/ceph/mds_client.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > index b1746273f186..4fa471d9b3b2 100644
> > --- a/fs/ceph/mds_client.c
> > +++ b/fs/ceph/mds_client.c
> > @@ -4956,7 +4956,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
> >  	/* placeholder for nr_caps */
> >  	err = ceph_pagelist_encode_32(recon_state.pagelist, 0);
> >  	if (err)
> > -		goto fail;
> > +		goto fail_clear_cap_reconnect;
> >  
> >  	if (test_bit(CEPHFS_FEATURE_MULTI_RECONNECT, &session->s_features)) {
> >  		recon_state.msg_version = 3;
> > @@ -5046,6 +5046,10 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc,
> >  	ceph_pagelist_release(recon_state.pagelist);
> >  	return;
> >  
> > +fail_clear_cap_reconnect:
> > +	spin_lock(&session->s_cap_lock);
> > +	session->s_cap_reconnect = 0;
> > +	spin_unlock(&session->s_cap_lock);
> >  fail:
> >  	ceph_msg_put(reply);
> >  	up_read(&mdsc->snap_rwsem);
> 
> Makes sense. Nice fix. But, maybe, we need to consider refactoring of this
> function because of such issue.
> 
> Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>
> 
> 

The xfstests run on 7.0-rc6 didn't reveal any new issues related to the patch.

Tested-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>

Thanks,
Slava.