Re: [RFC PATCH 0/4] ceph: fix spurious recover_session=clean errors

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2020-09-29 at 12:58 +0200, Ilya Dryomov wrote:
> On Tue, Sep 29, 2020 at 12:44 PM Yan, Zheng <ukernel@gmail.com> wrote:
> > On Tue, Sep 29, 2020 at 4:55 PM Ilya Dryomov <idryomov@gmail.com> wrote:
> > > On Tue, Sep 29, 2020 at 10:28 AM Yan, Zheng <ukernel@gmail.com> wrote:
> > > > On Fri, Sep 25, 2020 at 10:08 PM Jeff Layton <jlayton@kernel.org> wrote:
> > > > > Ilya noticed that he would get spurious EACCES errors on calls done just
> > > > > after blocklisting the client on mounts with recover_session=clean. The
> > > > > session would get marked as REJECTED and that caused in-flight calls to
> > > > > die with EACCES. This patchset seems to smooth over the problem, but I'm
> > > > > not fully convinced it's the right approach.
> > > > > 
> > > > 
> > > > the root is cause is that client does not recover session instantly
> > > > after getting rejected by mds. Before session gets recovered, client
> > > > continues to return error.
> > > 
> > > Hi Zheng,
> > > 
> > > I don't think it's about whether that happens instantly or not.
> > > In the example from [1], the first "ls" would fail even if issued
> > > minutes after the session reject message and the reconnect.  From
> > > the user's POV it is well after the automatic recovery promised by
> > > recover_session=clean.
> > > 
> > > [1] https://tracker.ceph.com/issues/47385
> > 
> > Reconnect should close all old session. It's likely because that
> > client didn't detect it's blacklisted.
> 
> Sorry, I should have pasted dmesg there as well.  It _does_ detect
> blacklisting -- notice that I wrote "after the session reject message
> and the reconnect".
> 

Yep, this is pretty easy to reproduce too (as Ilya points out in the tracker).

I'm open to other ways of smoothing this over. If we end up with a small
window where errors can occur, then so be it, but I think we can
probably do better than we have now.

-- 
Jeff Layton <jlayton@kernel.org>