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@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 53 insertions, 15 deletions

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 4704dce7284e..39516b2cca9e 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 +870,60 @@ 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. On failure, some pools may have already been
+ * adjusted; the caller is responsible for recovery.
+ */
+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 = 0;
+
+	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);
 
 /**