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Message-Id: <20260106-nfsd-dynathread-v2-1-416e5f27b2b6@kernel.org>
Date: Tue, 06 Jan 2026 13:59:43 -0500
From: Jeff Layton <jlayton@...nel.org>
To: 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: linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v2 1/8] sunrpc: split svc_set_num_threads() into two
functions
svc_set_num_threads() will set the number of running threads for a given
pool. If the pool argument is set to NULL however, it will distribute
the threads among all of the pools evenly.
These divergent codepaths complicate the move to dynamic threading.
Simplify the API by splitting these two cases into different helpers:
Add a new svc_set_pool_threads() function that sets the number of
threads in a single, given pool. Modify svc_set_num_threads() to
distribute the threads evenly between all of the pools and then call
svc_set_pool_threads() for each.
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
fs/lockd/svc.c | 4 +--
fs/nfs/callback.c | 8 +++---
fs/nfsd/nfssvc.c | 21 +++++++--------
include/linux/sunrpc/svc.h | 4 ++-
net/sunrpc/svc.c | 67 +++++++++++++++++++++++++++++++++++-----------
5 files changed, 70 insertions(+), 34 deletions(-)
diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index d68afa196535a8785bab2931c2b14f03a1174ef9..fbf132b4e08d11a91784c21ee0209fd7c149fd9d 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -340,7 +340,7 @@ static int lockd_get(void)
return -ENOMEM;
}
- error = svc_set_num_threads(serv, NULL, 1);
+ error = svc_set_num_threads(serv, 1);
if (error < 0) {
svc_destroy(&serv);
return error;
@@ -368,7 +368,7 @@ static void lockd_put(void)
unregister_inet6addr_notifier(&lockd_inet6addr_notifier);
#endif
- svc_set_num_threads(nlmsvc_serv, NULL, 0);
+ svc_set_num_threads(nlmsvc_serv, 0);
timer_delete_sync(&nlmsvc_retry);
svc_destroy(&nlmsvc_serv);
dprintk("lockd_down: service destroyed\n");
diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index fabda0f6ec1a8ab1017553b755693a4a371f578d..d01de143927bfeab2b44e60928512a03183e7244 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -119,9 +119,9 @@ static int nfs_callback_start_svc(int minorversion, struct rpc_xprt *xprt,
if (serv->sv_nrthreads == nrservs)
return 0;
- ret = svc_set_num_threads(serv, NULL, nrservs);
+ ret = svc_set_num_threads(serv, nrservs);
if (ret) {
- svc_set_num_threads(serv, NULL, 0);
+ svc_set_num_threads(serv, 0);
return ret;
}
dprintk("nfs_callback_up: service started\n");
@@ -242,7 +242,7 @@ int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
cb_info->users++;
err_net:
if (!cb_info->users) {
- svc_set_num_threads(cb_info->serv, NULL, 0);
+ svc_set_num_threads(cb_info->serv, 0);
svc_destroy(&cb_info->serv);
}
err_create:
@@ -268,7 +268,7 @@ void nfs_callback_down(int minorversion, struct net *net, struct rpc_xprt *xprt)
nfs_callback_down_net(minorversion, serv, net);
cb_info->users--;
if (cb_info->users == 0) {
- svc_set_num_threads(serv, NULL, 0);
+ svc_set_num_threads(serv, 0);
dprintk("nfs_callback_down: service destroyed\n");
xprt_svc_destroy_nullify_bc(xprt, &cb_info->serv);
}
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index f1cc223ecee2f6ea5bd1d88abf1b0569bc430238..049165ee26afca9f3d6d4ba471823597c93262a5 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -580,7 +580,7 @@ void nfsd_shutdown_threads(struct net *net)
}
/* Kill outstanding nfsd threads */
- svc_set_num_threads(serv, NULL, 0);
+ svc_set_num_threads(serv, 0);
nfsd_destroy_serv(net);
mutex_unlock(&nfsd_mutex);
}
@@ -688,12 +688,9 @@ int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
if (nn->nfsd_serv == NULL || n <= 0)
return 0;
- /*
- * Special case: When n == 1, pass in NULL for the pool, so that the
- * change is distributed equally among them.
- */
+ /* Special case: When n == 1, distribute threads equally among pools. */
if (n == 1)
- return svc_set_num_threads(nn->nfsd_serv, NULL, nthreads[0]);
+ return svc_set_num_threads(nn->nfsd_serv, nthreads[0]);
if (n > nn->nfsd_serv->sv_nrpools)
n = nn->nfsd_serv->sv_nrpools;
@@ -719,18 +716,18 @@ int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
/* apply the new numbers */
for (i = 0; i < n; i++) {
- err = svc_set_num_threads(nn->nfsd_serv,
- &nn->nfsd_serv->sv_pools[i],
- nthreads[i]);
+ err = svc_set_pool_threads(nn->nfsd_serv,
+ &nn->nfsd_serv->sv_pools[i],
+ nthreads[i]);
if (err)
goto out;
}
/* Anything undefined in array is considered to be 0 */
for (i = n; i < nn->nfsd_serv->sv_nrpools; ++i) {
- err = svc_set_num_threads(nn->nfsd_serv,
- &nn->nfsd_serv->sv_pools[i],
- 0);
+ err = svc_set_pool_threads(nn->nfsd_serv,
+ &nn->nfsd_serv->sv_pools[i],
+ 0);
if (err)
goto out;
}
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 5506d20857c318774cd223272d4b0022cc19ffb8..2676bf276d6ba43772ecee65b94207b438168679 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -446,7 +446,9 @@ struct svc_serv * svc_create_pooled(struct svc_program *prog,
struct svc_stat *stats,
unsigned int bufsize,
int (*threadfn)(void *data));
-int svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
+int svc_set_pool_threads(struct svc_serv *serv, struct svc_pool *pool,
+ unsigned int nrservs);
+int svc_set_num_threads(struct svc_serv *serv, unsigned int nrservs);
int svc_pool_stats_open(struct svc_info *si, struct file *file);
void svc_process(struct svc_rqst *rqstp);
void svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 4704dce7284eccc9e2bc64cf22947666facfa86a..cd9d4f8b75aeb6ffa08ce84a0b82da7fd37e6fbf 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -856,15 +856,12 @@ svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
}
/**
- * svc_set_num_threads - adjust number of threads per RPC service
+ * svc_set_pool_threads - adjust number of threads per pool
* @serv: RPC service to adjust
- * @pool: Specific pool from which to choose threads, or NULL
- * @nrservs: New number of threads for @serv (0 or less means kill all threads)
+ * @pool: Specific pool from which to choose threads
+ * @nrservs: New number of threads for @serv (0 means kill all threads)
*
- * Create or destroy threads to make the number of threads for @serv the
- * given number. If @pool is non-NULL, change only threads in that pool;
- * otherwise, round-robin between all pools for @serv. @serv's
- * sv_nrthreads is adjusted for each thread created or destroyed.
+ * Create or destroy threads in @pool to bring it to @nrservs.
*
* Caller must ensure mutual exclusion between this and server startup or
* shutdown.
@@ -873,19 +870,59 @@ svc_stop_kthreads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
* starting a thread.
*/
int
-svc_set_num_threads(struct svc_serv *serv, struct svc_pool *pool, int nrservs)
+svc_set_pool_threads(struct svc_serv *serv, struct svc_pool *pool,
+ unsigned int nrservs)
{
+ int delta = nrservs;
+
if (!pool)
- nrservs -= serv->sv_nrthreads;
- else
- nrservs -= pool->sp_nrthreads;
+ return -EINVAL;
- if (nrservs > 0)
- return svc_start_kthreads(serv, pool, nrservs);
- if (nrservs < 0)
- return svc_stop_kthreads(serv, pool, nrservs);
+ delta -= pool->sp_nrthreads;
+
+ if (delta > 0)
+ return svc_start_kthreads(serv, pool, delta);
+ if (delta < 0)
+ return svc_stop_kthreads(serv, pool, delta);
return 0;
}
+EXPORT_SYMBOL_GPL(svc_set_pool_threads);
+
+/**
+ * svc_set_num_threads - adjust number of threads in serv
+ * @serv: RPC service to adjust
+ * @nrservs: New number of threads for @serv (0 means kill all threads)
+ *
+ * Create or destroy threads in @serv to bring it to @nrservs. If there
+ * are multiple pools then the new threads or victims will be distributed
+ * evenly among them.
+ *
+ * Caller must ensure mutual exclusion between this and server startup or
+ * shutdown.
+ *
+ * Returns zero on success or a negative errno if an error occurred while
+ * starting a thread.
+ */
+int
+svc_set_num_threads(struct svc_serv *serv, unsigned int nrservs)
+{
+ unsigned int base = nrservs / serv->sv_nrpools;
+ unsigned int remain = nrservs % serv->sv_nrpools;
+ int i, err;
+
+ for (i = 0; i < serv->sv_nrpools; ++i) {
+ int threads = base;
+
+ if (remain) {
+ ++threads;
+ --remain;
+ }
+ err = svc_set_pool_threads(serv, &serv->sv_pools[i], threads);
+ if (err)
+ break;
+ }
+ return err;
+}
EXPORT_SYMBOL_GPL(svc_set_num_threads);
/**
--
2.52.0
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