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Subject: Re: [PATCH RFC] nfsd: fix error handling in nfsd_svc
From:   Jeff Layton <jlayton@kernel.org>
To:     NeilBrown <neilb@suse.de>
Cc:     Chuck Lever <chuck.lever@oracle.com>,
        Olga Kornievskaia <kolga@netapp.com>,
        Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
        linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zhi Li <yieli@redhat.com>
Date:   Mon, 30 Oct 2023 17:43:20 -0400
In-Reply-To: <169870163037.24305.14020614041859684912@noble.neil.brown.name>
References: <20231030-kdevops-v1-1-bae6baf62c69@kernel.org>
         <169870163037.24305.14020614041859684912@noble.neil.brown.name>
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On Tue, 2023-10-31 at 08:33 +1100, NeilBrown wrote:
> On Tue, 31 Oct 2023, Jeff Layton wrote:
> > Once we've set the nfsd_serv pointer in nfsd_svc, we still need to call
> > nfsd_last_thread if the server fails to be started. Remove the special
> > casing for nfsd_up_before case since shutting down the per-net stuff is
> > also handled by nfsd_last_thread.
> >=20
> > Finally, add a new special case at the start and skip doing anything if
> > the service already exists, 0 threads were requested and
> > serv->sv_nrthreads is 0.
>=20
> This is very similar to my=20
>   Commit bf32075256e9 ("NFSD: simplify error paths in nfsd_svc()")
>=20
> The main difference being that special case you mention.  I don't like
> that bit.
> If I run "rpc.nfsd 0" then I want the nfsd_svc to be destroyed, whether
> there were threads running or not.
>=20
> Is there a reason my patch isn't sufficient?
>=20

Ok, I wasn't sure whether that was the desired behavior or not. Your
patch should be fine actually, and it has already had some testing, so
let's just mark that for stable?


> Thanks,
> NeilBrown
>=20
>=20
> >=20
> > Fixes: 9f28a971ee9f ("nfsd: separate nfsd_last_thread() from nfsd_put()=
")
> > Reported-by: Zhi Li <yieli@redhat.com>
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> > Here's what I was thinking for a targeted patch for stable. Testing it
> > now, but I won't have results until tomorrow.
> > ---
> >  fs/nfsd/nfssvc.c | 15 +++++----------
> >  1 file changed, 5 insertions(+), 10 deletions(-)
> >=20
> > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> > index 3deef000afa9..187b68769815 100644
> > --- a/fs/nfsd/nfssvc.c
> > +++ b/fs/nfsd/nfssvc.c
> > @@ -787,7 +787,6 @@ int
> >  nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
> >  {
> >  	int	error;
> > -	bool	nfsd_up_before;
> >  	struct nfsd_net *nn =3D net_generic(net, nfsd_net_id);
> >  	struct svc_serv *serv;
> > =20
> > @@ -797,8 +796,9 @@ nfsd_svc(int nrservs, struct net *net, const struct=
 cred *cred)
> >  	nrservs =3D max(nrservs, 0);
> >  	nrservs =3D min(nrservs, NFSD_MAXSERVS);
> >  	error =3D 0;
> > +	serv =3D nn->nfsd_serv;
> > =20
> > -	if (nrservs =3D=3D 0 && nn->nfsd_serv =3D=3D NULL)
> > +	if (nrservs =3D=3D 0 && (serv =3D=3D NULL || serv->sv_nrthreads =3D=
=3D 0))
> >  		goto out;
> > =20
> >  	strscpy(nn->nfsd_name, utsname()->nodename,
> > @@ -808,22 +808,17 @@ nfsd_svc(int nrservs, struct net *net, const stru=
ct cred *cred)
> >  	if (error)
> >  		goto out;
> > =20
> > -	nfsd_up_before =3D nn->nfsd_net_up;
> >  	serv =3D nn->nfsd_serv;
> > =20
> >  	error =3D nfsd_startup_net(net, cred);
> >  	if (error)
> >  		goto out_put;
> >  	error =3D svc_set_num_threads(serv, NULL, nrservs);
> > -	if (error)
> > -		goto out_shutdown;
> > -	error =3D serv->sv_nrthreads;
> >  	if (error =3D=3D 0)
> > -		nfsd_last_thread(net);
> > -out_shutdown:
> > -	if (error < 0 && !nfsd_up_before)
> > -		nfsd_shutdown_net(net);
> > +		error =3D serv->sv_nrthreads;
> >  out_put:
> > +	if (serv->sv_nrthreads =3D=3D 0)
> > +		nfsd_last_thread(net);
> >  	/* Threads now hold service active */
> >  	if (xchg(&nn->keep_active, 0))
> >  		svc_put(serv);
> >=20
> > ---
> > base-commit: 31b5a36c4b88b44c91cdd523997b1e86fb47339d
> > change-id: 20231030-kdevops-5f7366897ef4
> >=20
> > Best regards,
> > --=20
> > Jeff Layton <jlayton@kernel.org>
> >=20
> >=20
>=20

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