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>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 113cd2512ba7aebf363e51b5936a2b37ad00f2e1..79c1e74263a19876c9e6cf6f4a34fbd3332c3473 100644 (file)
--- 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;
        }