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Message-ID: <fe33e7c5b42b15448340ebc57fc294f479381c0d.camel@kernel.org>
Subject: Re: [PATCH 0/5 v2] sunrpc: stop refcounting svc_serv
From: Jeff Layton <jlayton@kernel.org>
To: Chuck Lever III <chuck.lever@oracle.com>, Neil Brown <neilb@suse.de>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>, Olga Kornievskaia
 <kolga@netapp.com>, Dai Ngo <dai.ngo@oracle.com>, Tom Talpey
 <tom@talpey.com>,  Lorenzo Bianconi <lorenzo@kernel.org>
Date: Fri, 15 Dec 2023 10:44:58 -0500
In-Reply-To: <C91850FB-094B-4D31-9CED-0C8C107645CE@oracle.com>
References: <20231215010030.7580-1-neilb@suse.de>
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	 <c8b275c3a9b168e8e4b4a4b4e921e913428294a7.camel@kernel.org>
	 <C923978C-5171-4394-A3F7-101E07092EBD@oracle.com>
	 <C91850FB-094B-4D31-9CED-0C8C107645CE@oracle.com>
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On Fri, 2023-12-15 at 15:37 +0000, Chuck Lever III wrote:
> > On Dec 15, 2023, at 9:38=E2=80=AFAM, Chuck Lever III <chuck.lever@oracl=
e.com> wrote:
> >=20
> > > On Dec 15, 2023, at 9:26=E2=80=AFAM, Jeff Layton <jlayton@kernel.org>=
 wrote:
> > >=20
> > > On Fri, 2023-12-15 at 14:19 +0000, Chuck Lever III wrote:
> > > > > On Dec 15, 2023, at 5:59=E2=80=AFAM, Jeff Layton <jlayton@kernel.=
org> wrote:
> > > > >=20
> > > > > On Fri, 2023-12-15 at 11:56 +1100, NeilBrown wrote:
> > > > > > I sent an earlier version of this series, got some feed back, r=
evised
> > > > > > it, but never sent it again.  Sorry.
> > > > > >=20
> > > > > > The main feedback was around the interaction between sunrpc and=
 nfsd for
> > > > > > handling poolstats.  I have changed that so that nfsd tells sun=
rpc where
> > > > > > the svc_serv pointer lives, and where to find a mutex to protec=
t it.
> > > > > > sunrpc then taks the mutex and accesses the pointer - if not NU=
LL.  I
> > > > > > think this is nicer than the version that pass around funciton =
pointers.
> > > > > >=20
> > > > > > This series is against nfsd-next
> > > > > >=20
> > > > > > Thanks,
> > > > > > NeilBrown
> > > > > >=20
> > > > > >=20
> > > > > > [PATCH 1/5] nfsd: call nfsd_last_thread() before final nfsd_put=
()
> > > > > > [PATCH 2/5] svc: don't hold reference for poolstats, only mutex=
.
> > > > > > [PATCH 3/5] nfsd: hold nfsd_mutex across entire netlink operati=
on
> > > > > > [PATCH 4/5] SUNRPC: discard sv_refcnt, and svc_get/svc_put
> > > > > > [PATCH 5/5] nfsd: rename nfsd_last_thread() to nfsd_destroy_ser=
v()
> > > > >=20
> > > > > I'm not sure patch #2 is better than the version with function po=
inters,
> > > > > but it seems reasonable.
> > > > >=20
> > > > > Note that patch #1 probably needs to go to v6.6 stable, and I thi=
nk we
> > > > > want #3 in v6.7 before it ships.
> > > >=20
> > > > Remind me why #3 should go into v6.7-rc ? There's no Fixes tag on
> > > > that one.
> > > >=20
> > > >=20
> > >=20
> > > It's the problem I noted to Lorenzo the other day:
> > >=20
> > >=20
> > > https://lore.kernel.org/linux-nfs/5d9bbb599569ce29f16e4e0eef6b291eda0=
f375b.camel@kernel.org/T/#u
> > >=20
> > > Once you've dropped the nfsd_mutex, there is no guarantee that
> > > nn->nfsd_serv will still be a valid pointer. Holding the mutex across
> > > the operation (like Neil's patch does), should close the race.
> >=20
> > OK. I'll add:
> >=20
> > =C2=A0Fixes: bd9d6a3efa97 ("NFSD: add rpc_status netlink support")
> >=20
> > I will apply 1/3 and 3/3 to v6.7-rc, and the others will go to
> > v6.8 (nfsd-next) once it is rebased on v6.7-rc7.
>=20
> Please check the two patches at the tip of the nfsd-fixes
> branch here:
>=20
> https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git
>=20
> I plan to apply the other three in this series to nfsd-next.
>=20
>=20

They look good to me.

Thanks,
--=20
Jeff Layton <jlayton@kernel.org>