tunnels: add __rcu annotations

Add __rcu annotations to :
        (struct ip_tunnel)->prl
        (struct ip_tunnel_prl_entry)->next
        (struct xfrm_tunnel)->next
	struct xfrm_tunnel *tunnel4_handlers
	struct xfrm_tunnel *tunnel64_handlers

And use appropriate rcu primitives to reduce sparse warnings if
CONFIG_SPARSE_RCU_POINTER=y

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 22 insertions, 13 deletions

diff --git a/include/net/ipip.h b/include/net/ipip.h
index 0403fe4c4519..a32654d52730 100644
--- a/include/net/ipip.h
+++ b/include/net/ipip.h
@@ -34,12 +34,12 @@ struct ip_tunnel {
 #ifdef CONFIG_IPV6_SIT_6RD
         struct ip_tunnel_6rd_parm       ip6rd;
 #endif
-        struct ip_tunnel_prl_entry      *prl;           /* potential router list */
+        struct ip_tunnel_prl_entry __rcu *prl;          /* potential router list */
         unsigned int                    prl_count;      /* # of entries in PRL */
 };
 
 struct ip_tunnel_prl_entry {
-        struct ip_tunnel_prl_entry      *next;
+        struct ip_tunnel_prl_entry __rcu *next;
         __be32                          addr;
         u16                             flags;
         struct rcu_head                 rcu_head;
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index ffcd47820a5b..bcfb6b24b019 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1264,7 +1264,7 @@ struct xfrm_tunnel {
         int (*handler)(struct sk_buff *skb);
         int (*err_handler)(struct sk_buff *skb, u32 info);
 
-        struct xfrm_tunnel *next;
+        struct xfrm_tunnel __rcu *next;
         int priority;
 };
 
diff --git a/net/ipv4/tunnel4.c b/net/ipv4/tunnel4.c
index 9a17bd2a0a37..ac3b3ee4b07c 100644
--- a/net/ipv4/tunnel4.c
+++ b/net/ipv4/tunnel4.c
@@ -14,27 +14,32 @@
 #include <net/protocol.h>
 #include <net/xfrm.h>
 
-static struct xfrm_tunnel *tunnel4_handlers __read_mostly;
-static struct xfrm_tunnel *tunnel64_handlers __read_mostly;
+static struct xfrm_tunnel __rcu *tunnel4_handlers __read_mostly;
+static struct xfrm_tunnel __rcu *tunnel64_handlers __read_mostly;
 static DEFINE_MUTEX(tunnel4_mutex);
 
-static inline struct xfrm_tunnel **fam_handlers(unsigned short family)
+static inline struct xfrm_tunnel __rcu **fam_handlers(unsigned short family)
 {
         return (family == AF_INET) ? &tunnel4_handlers : &tunnel64_handlers;
 }
 
 int xfrm4_tunnel_register(struct xfrm_tunnel *handler, unsigned short family)
 {
-        struct xfrm_tunnel **pprev;
+        struct xfrm_tunnel __rcu **pprev;
+        struct xfrm_tunnel *t;
+
         int ret = -EEXIST;
         int priority = handler->priority;
 
         mutex_lock(&tunnel4_mutex);
 
-        for (pprev = fam_handlers(family); *pprev; pprev = &(*pprev)->next) {
-                if ((*pprev)->priority > priority)
+        for (pprev = fam_handlers(family);
+             (t = rcu_dereference_protected(*pprev,
+                        lockdep_is_held(&tunnel4_mutex))) != NULL;
+             pprev = &t->next) {
+                if (t->priority > priority)
                         break;
-                if ((*pprev)->priority == priority)
+                if (t->priority == priority)
                         goto err;
         }
 
@@ -52,13 +57,17 @@ EXPORT_SYMBOL(xfrm4_tunnel_register);
 
 int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler, unsigned short family)
 {
-        struct xfrm_tunnel **pprev;
+        struct xfrm_tunnel __rcu **pprev;
+        struct xfrm_tunnel *t;
         int ret = -ENOENT;
 
         mutex_lock(&tunnel4_mutex);
 
-        for (pprev = fam_handlers(family); *pprev; pprev = &(*pprev)->next) {
-                if (*pprev == handler) {
+        for (pprev = fam_handlers(family);
+             (t = rcu_dereference_protected(*pprev,
+                        lockdep_is_held(&tunnel4_mutex))) != NULL;
+             pprev = &t->next) {
+                if (t == handler) {
                         *pprev = handler->next;
                         ret = 0;
                         break;