[PATCH]IPv6: Acquire addrconf_hash_lock for reading instead of writing in addrconf_verify(...)

[Yan Zheng <yanzheng@21cn.com>]

Hi.

addrconf_verify(...) only traverse address hash table when addrconf_hash_lock is held
for writing, and it may hold addrconf_hash_lock for a long time. So I think it's better
to acquire addrconf_hash_lock for reading instead of  writing

Signed-off-by: Yan Zheng <yanzheng@21cn.com>

============================================================
--- a/net/ipv6/addrconf.c	2005-11-17 09:27:54.000000000 +0800
+++ b/net/ipv6/addrconf.c	2005-11-17 09:25:42.000000000 +0800
@@ -2627,7 +2627,7 @@ static void addrconf_verify(unsigned lon
	for (i=0; i < IN6_ADDR_HSIZE; i++) {

restart:
-		write_lock(&addrconf_hash_lock);
+		read_lock(&addrconf_hash_lock);
		for (ifp=inet6_addr_lst[i]; ifp; ifp=ifp->lst_next) {
			unsigned long age;
#ifdef CONFIG_IPV6_PRIVACY
@@ -2649,7 +2649,7 @@ restart:
			if (age >= ifp->valid_lft) {
				spin_unlock(&ifp->lock);
				in6_ifa_hold(ifp);
-				write_unlock(&addrconf_hash_lock);
+				read_unlock(&addrconf_hash_lock);
				ipv6_del_addr(ifp);
				goto restart;
			} else if (age >= ifp->prefered_lft) {
@@ -2668,7 +2668,7 @@ restart:

				if (deprecate) {
					in6_ifa_hold(ifp);
-					write_unlock(&addrconf_hash_lock);
+					read_unlock(&addrconf_hash_lock);

					ipv6_ifa_notify(0, ifp);
					in6_ifa_put(ifp);
@@ -2686,7 +2686,7 @@ restart:
						in6_ifa_hold(ifp);
						in6_ifa_hold(ifpub);
						spin_unlock(&ifp->lock);
-						write_unlock(&addrconf_hash_lock);
+						read_unlock(&addrconf_hash_lock);
						ipv6_create_tempaddr(ifpub, ifp);
						in6_ifa_put(ifpub);
						in6_ifa_put(ifp);
@@ -2703,7 +2703,7 @@ restart:
				spin_unlock(&ifp->lock);
			}
		}
-		write_unlock(&addrconf_hash_lock);
+		read_unlock(&addrconf_hash_lock);
	}

	addr_chk_timer.expires = time_before(next, jiffies + HZ) ? jiffies + HZ : next;
-
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