From: Eric Dumazet <edumazet@google.com>
Date: Fri, 25 Feb 2022 16:18:55 +0000 (-0800)
Subject: net/sysctl: avoid two synchronize_rcu() calls
X-Git-Tag: v5.18-rc1~136^2~241
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b3483bc7a1f2673b35331e60668104ba2be46510;p=thirdparty%2Flinux.git

net/sysctl: avoid two synchronize_rcu() calls

Both rps_sock_flow_sysctl() and flow_limit_cpu_sysctl()
are using synchronize_rcu() right before freeing memory
either by vfree() or kfree()

They can switch to kvfree_rcu(ptr) and kfree_rcu(ptr) to benefit
from asynchronous mode, instead of blocking the current thread.

Note that kvfree_rcu(ptr) and kfree_rcu(ptr) eventually can
have to use synchronize_rcu() in some memory pressure cases.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index dbeb8ecbcd98f..7123fe7feeac6 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -103,8 +103,7 @@ static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
 			if (orig_sock_table) {
 				static_branch_dec(&rps_needed);
 				static_branch_dec(&rfs_needed);
-				synchronize_rcu();
-				vfree(orig_sock_table);
+				kvfree_rcu(orig_sock_table);
 			}
 		}
 	}
@@ -142,8 +141,7 @@ static int flow_limit_cpu_sysctl(struct ctl_table *table, int write,
 				     lockdep_is_held(&flow_limit_update_mutex));
 			if (cur && !cpumask_test_cpu(i, mask)) {
 				RCU_INIT_POINTER(sd->flow_limit, NULL);
-				synchronize_rcu();
-				kfree(cur);
+				kfree_rcu(cur);
 			} else if (!cur && cpumask_test_cpu(i, mask)) {
 				cur = kzalloc_node(len, GFP_KERNEL,
 						   cpu_to_node(i));