1 files changed, 52 insertions, 2 deletions

diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 8e9a672320ab..c808e2662857 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/net.h>
 #include <linux/string.h>
+#include <linux/sched.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/list.h>
@@ -30,6 +31,7 @@
 #include <linux/module.h>
 #include <keys/user-type.h>
 #include <net/ipv6.h>
+#include <net/route.h>
 #include <linux/parser.h>
 #include <linux/bvec.h>
 #include "cifspdu.h"
@@ -67,6 +69,8 @@ static int generic_ip_connect(struct TCP_Server_Info *server);
 static void tlink_rb_insert(struct rb_root *root, struct tcon_link *new_tlink);
 static void cifs_prune_tlinks(struct work_struct *work);
 
+static int cifsd_rr_last_cpu = -1;
+
 /*
  * Resolve hostname and set ip addr in tcp ses. Useful for hostnames that may
  * get their ip addresses changed at some point.
@@ -1550,6 +1554,45 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 		send_sig(SIGKILL, task, 1);
 }
 
+/**
+ * __smb_get_next_cpu: return the next online CPU, globally accounted by @cifsd_rr_last_cpu
+ */
+static inline int __smb_get_next_cpu(void)
+{
+	int cpu;
+
+	cpu = cpumask_next_wrap(cifsd_rr_last_cpu, cpu_online_mask, -1, false);
+	if (unlikely(cpu >= nr_cpu_ids)) {
+		cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
+		if (unlikely(cpu >= nr_cpu_ids)) {
+			/* last resort */
+			cpu = raw_smp_processor_id();
+		}
+	}
+
+	cifsd_rr_last_cpu = cpu;
+	return cifsd_rr_last_cpu;
+}
+
+/**
+ * smb_get_cifsd_task: return a task_struct for cifsd, based on @server::cpu_policy_affine
+ *
+ * @server::cpu_policy_affine behaviour:
+ * true: create the task via kthread_run() which will let the scheduler pick the best CPU to use
+ * false: create the task via kthread_run_on_cpu(), with its @cpu argument set to the next
+ *	  online CPU, which is chosen in a round-robin manner in __smb_get_next_cpu() and tracked
+ *	  via global %cifsd_rr_last_cpu
+ */
+static inline struct task_struct *smb_get_cifsd_task(struct TCP_Server_Info *server)
+{
+	if (!server->cpu_policy_affine || num_online_cpus() == 1)
+		return kthread_run(cifs_demultiplex_thread, server, "cifsd");
+
+	/* cpu_policy=affine */
+	return kthread_run_on_cpu(cifs_demultiplex_thread, server, __smb_get_next_cpu(),
+				  "cifsd");
+}
+
 struct TCP_Server_Info *
 cifs_get_tcp_session(struct smb3_fs_context *ctx,
 		     struct TCP_Server_Info *primary_server)
@@ -1680,14 +1723,21 @@ smbd_connected:
 	 * this will succeed. No need for try_module_get().
 	 */
 	__module_get(THIS_MODULE);
-	tcp_ses->tsk = kthread_run(cifs_demultiplex_thread,
-				  tcp_ses, "cifsd");
+
+	tcp_ses->cpu_policy_affine = tcp_ses->primary_server ?
+				     tcp_ses->primary_server->cpu_policy_affine :
+				     ctx->cpu_policy_affine;
+	tcp_ses->tsk = smb_get_cifsd_task(tcp_ses);
 	if (IS_ERR(tcp_ses->tsk)) {
 		rc = PTR_ERR(tcp_ses->tsk);
 		cifs_dbg(VFS, "error %d create cifsd thread\n", rc);
 		module_put(THIS_MODULE);
 		goto out_err_crypto_release;
 	}
+
+	cifs_dbg(FYI, "%s: running cifsd task 0x%p on CPU#%d\n",
+		 __func__, tcp_ses->tsk, tcp_ses->tsk_cpu);
+
 	tcp_ses->min_offload = ctx->min_offload;
 	/*
 	 * at this point we are the only ones with the pointer