linux-kernel - [PATCH 1/2] nfsd: use threads array as-is in netlink interface

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Message-Id: <20250527-rpc-numa-v1-1-fa1d98e9a900@kernel.org>
Date: Tue, 27 May 2025 20:12:47 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>, 
 Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, 
 Tom Talpey <tom@...pey.com>, Steven Rostedt <rostedt@...dmis.org>, 
 Masami Hiramatsu <mhiramat@...nel.org>, 
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
 Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>
Cc: Mike Snitzer <snitzer@...nel.org>, linux-nfs@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
 netdev@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 1/2] nfsd: use threads array as-is in netlink interface

The old nfsdfs interface for starting a server with multiple pools
handles the special case of a single entry array passed down from
userland by distributing the threads over every NUMA node.

The netlink control interface however constructs an array of length
nfsd_nrpools() and fills any unprovided slots with 0's. This behavior
defeats the special casing that the old interface relies on.

Change nfsd_nl_threads_set_doit() to pass down the array from userland
as-is.

Fixes: 7f5c330b2620 ("nfsd: allow passing in array of thread counts via netlink")
Reported-by: Mike Snitzer <snitzer@...nel.org>
Closes: https://lore.kernel.org/linux-nfs/aDC-ftnzhJAlwqwh@kernel.org/
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 fs/nfsd/nfsctl.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index ac265d6fde35df4e02b955050f5b0ef22e6e519c..22101e08c3e80350668e94c395058bc228b08e64 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1611,7 +1611,7 @@ int nfsd_nl_rpc_status_get_dumpit(struct sk_buff *skb,
  */
 int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	int *nthreads, count = 0, nrpools, i, ret = -EOPNOTSUPP, rem;
+	int *nthreads, nrpools = 0, i, ret = -EOPNOTSUPP, rem;
 	struct net *net = genl_info_net(info);
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 	const struct nlattr *attr;
@@ -1623,12 +1623,11 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
 	/* count number of SERVER_THREADS values */
 	nlmsg_for_each_attr(attr, info->nlhdr, GENL_HDRLEN, rem) {
 		if (nla_type(attr) == NFSD_A_SERVER_THREADS)
-			count++;
+			nrpools++;
 	}

 	mutex_lock(&nfsd_mutex);

-	nrpools = max(count, nfsd_nrpools(net));
 	nthreads = kcalloc(nrpools, sizeof(int), GFP_KERNEL);
 	if (!nthreads) {
 		ret = -ENOMEM;

-- 
2.49.0