linux-kernel - Re: [PATCH 1/2] nfsd/sunrpc: add svc_rqst->rq_private pointer and remove rq_lease

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Message-ID: <3b5faf0e9bb08c779854e3aaa8b30fb12e86b25e.camel@kernel.org>
Date: Tue, 13 Jan 2026 15:12:38 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <cel@...nel.org>, Chuck Lever <chuck.lever@...cle.com>, 
 NeilBrown <neil@...wn.name>, Olga Kornievskaia <okorniev@...hat.com>, Dai
 Ngo <Dai.Ngo@...cle.com>,  Tom Talpey <tom@...pey.com>, Trond Myklebust
 <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>
Cc: Benjamin Coddington <bcodding@...merspace.com>,
 linux-nfs@...r.kernel.org, 	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] nfsd/sunrpc: add svc_rqst->rq_private pointer and
 remove rq_lease_breaker

On Tue, 2026-01-13 at 14:41 -0500, Chuck Lever wrote:
> 
> On Tue, Jan 13, 2026, at 2:31 PM, Jeff Layton wrote:
> > On Tue, 2026-01-13 at 14:21 -0500, Chuck Lever wrote:
> > > 
> > > On Tue, Jan 13, 2026, at 1:37 PM, Jeff Layton wrote:
> > > > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> > > > index eee8c3f4a251a3fae6e41679de0ec34c76caf198..8ce366c9e49220e8baf475c2e5f3424fedc1cec1 100644
> > > > --- a/fs/nfsd/nfssvc.c
> > > > +++ b/fs/nfsd/nfssvc.c
> > > > @@ -900,6 +900,7 @@ nfsd(void *vrqstp)
> > > > struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);
> > > > struct net *net = perm_sock->xpt_net;
> > > > struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > > > + struct nfsd_thread_local_info ntli = { };
> > > > bool have_mutex = false;
> > > >  
> > > > /* At this point, the thread shares current->fs
> > > > @@ -914,6 +915,8 @@ nfsd(void *vrqstp)
> > > >  
> > > > set_freezable();
> > > >  
> > > > + rqstp->rq_private = &ntli;
> > > > +
> > > > /*
> > > > * The main request loop
> > > > */
> > > 
> > > Thanks for tackling this one. Nits below...
> > > 
> > > This assumes sizeof(structure nfsd_thread_local_info) will always
> > > be small enough that it is reasonable to keep on the stack. I
> > > can't say that would be a good bet in the long run.
> > > 
> > > And we don't need the perfect reliability of not doing a dynamic
> > > allocation here. If kmalloc(sizeof(struct nfsd_thread_local_info))
> > > fails, the thread exits immediately, no harm.
> > > 
> > 
> > Not sure how much space Ben will need (if any).
> > 
> > We certainly could have nfsd allocate this separately. I didn't see the
> > point for something that is only a few bytes though.
> 
> If we are designing for today, another approach would be to set up
> a BUILD_WARN_ON or other type of static build failure if this
> structure grows larger than, say 256 bytes -- then add dynamic
> allocation at that point.
> 

I don't see us growing this to huge proportions. I think that's the
sort of thing we just have to watch out for as maintainers.

If you really insist on a BUILD_WARN_ON tripwire, I'll add one, but it
seems like overkill to me.
-- 
Jeff Layton <jlayton@...nel.org>