ipv4: remove flush_mutex from ipv4_sysctl_rtcache_flush

It is possible to avoid locking at all in ipv4_sysctl_rtcache_flush by
defining local ctl_table on the stack.

The patch is based on the suggestion from Eric W. Biederman.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 8 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 113cd2512ba7..79c1e74263a1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2873,22 +2873,20 @@ void ip_rt_multicast_event(struct in_device *in_dev)
 }
 
 #ifdef CONFIG_SYSCTL
-static int ipv4_sysctl_rtcache_flush(ctl_table *ctl, int write,
+static int ipv4_sysctl_rtcache_flush(ctl_table *__ctl, int write,
                                         struct file *filp, void __user *buffer,
                                         size_t *lenp, loff_t *ppos)
 {
         if (write) {
                 int flush_delay;
+                ctl_table ctl;
                 struct net *net;
-                static DEFINE_MUTEX(flush_mutex);
 
-                mutex_lock(&flush_mutex);
-                ctl->data = &flush_delay;
-                proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
-                ctl->data = NULL;
-                mutex_unlock(&flush_mutex);
+                memcpy(&ctl, __ctl, sizeof(ctl));
+                ctl.data = &flush_delay;
+                proc_dointvec(&ctl, write, filp, buffer, lenp, ppos);
 
-                net = (struct net *)ctl->extra1;
+                net = (struct net *)__ctl->extra1;
                 rt_cache_flush(net, flush_delay);
                 return 0;
         }