linux-kernel - Re: [v3] ceph: if we are blacklisted, __do

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Message-ID: <CAB9OAC3fqvm9oigQour-jYuaSoh9Ny6Botk9Ls+ie-uKap19AQ@mail.gmail.com>
Date:   Tue, 21 Apr 2020 20:21:02 +0800
From:   Yanhu Cao <gmayyyha@...il.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [v3] ceph: if we are blacklisted, __do_request returns directly

On Tue, Apr 21, 2020 at 6:15 PM Jeff Layton <jlayton@...nel.org> wrote:
>
> On Tue, 2020-04-21 at 10:13 +0800, Yanhu Cao wrote:
> > On Mon, Apr 20, 2020 at 8:16 PM Jeff Layton <jlayton@...nel.org> wrote:
> > > On Fri, 2020-04-17 at 19:07 +0800, Yanhu Cao wrote:
> > > > If we mount cephfs by the recover_session option,
> > > > __do_request can return directly until the client automatically reconnects.
> > > >
> > > > Signed-off-by: Yanhu Cao <gmayyyha@...il.com>
> > > > ---
> > > >  fs/ceph/mds_client.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> > > > index 486f91f9685b..16ac5e5f7f79 100644
> > > > --- a/fs/ceph/mds_client.c
> > > > +++ b/fs/ceph/mds_client.c
> > > > @@ -2708,6 +2708,12 @@ static void __do_request(struct ceph_mds_client *mdsc,
> > > >
> > > >       put_request_session(req);
> > > >
> > > > +     if (mdsc->fsc->blacklisted &&
> > > > +         ceph_test_mount_opt(mdsc->fsc, CLEANRECOVER)) {
> > > > +             err = -EBLACKLISTED;
> > > > +             goto finish;
> > > > +     }
> > > > +
> > >
> > > Why check for CLEANRECOVER? If we're mounted with recover_session=no
> > > wouldn't we want to do the same thing here?
> > >
> > > Either way, it's still blacklisted. The only difference is that it won't
> > > attempt to automatically recover the session that way.
> >
> > I think mds will clear the blacklist. In addition to loading cephfs
> > via recover_session=clean, I didn't find a location where
> > fsc->blacklisted is set to false. If the client has been blacklisted,
> > should it always be blacklisted (fsc->blacklisted=true)? Or is there
> > another way to set fsc->blacklised to false?
> >
>
> Basically, this patch is just changing it so that when the client is
> blacklisted and the mount is done with recover_session=clean, we'll
> shortcut the rest of the __do_request and just return -EBLACKLISTED.
>
> My question is: why do we need to test for recover_session=clean here?

I thought that fsc->blacklisted is related to recovery_session=clean.
If we test it, the client can do the rest of __do_request. It seems
useless now because kcephfs cannot resume the session like ceph-fuse
when mds cleared the blacklist.

>
> If the client _knows_ that it is blacklisted, why would it want to
> continue with __do_request in the recover_session=no case? Would it make
> more sense to always return early in __do_request when the client is
> blacklisted?

Makes sense. if there is no problem. I will patch the next commit and
return -EBLACKLISTED only when fsc->blacklisted=true.

>
>
> > >
> > > >       mds = __choose_mds(mdsc, req, &random);
> > > >       if (mds < 0 ||
> > > >           ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
> > > --
> > > Jeff Layton <jlayton@...nel.org>
> > >
>
> --
> Jeff Layton <jlayton@...nel.org>
>