ipv4: add __rcu annotations to routes.c

Add __rcu annotations to :
        (struct dst_entry)->rt_next
        (struct rt_hash_bucket)->chain

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>

1 files changed, 46 insertions, 29 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d6cb2bfcd8e1..987bf9adb318 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -198,7 +198,7 @@ const __u8 ip_tos2prio[16] = {
  */
 
 struct rt_hash_bucket {
-        struct rtable   *chain;
+        struct rtable __rcu     *chain;
 };
 
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) || \
@@ -280,7 +280,7 @@ static struct rtable *rt_cache_get_first(struct seq_file *seq)
         struct rtable *r = NULL;
 
         for (st->bucket = rt_hash_mask; st->bucket >= 0; --st->bucket) {
-                if (!rt_hash_table[st->bucket].chain)
+                if (!rcu_dereference_raw(rt_hash_table[st->bucket].chain))
                         continue;
                 rcu_read_lock_bh();
                 r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
@@ -300,17 +300,17 @@ static struct rtable *__rt_cache_get_next(struct seq_file *seq,
 {
         struct rt_cache_iter_state *st = seq->private;
 
-        r = r->dst.rt_next;
+        r = rcu_dereference_bh(r->dst.rt_next);
         while (!r) {
                 rcu_read_unlock_bh();
                 do {
                         if (--st->bucket < 0)
                                 return NULL;
-                } while (!rt_hash_table[st->bucket].chain);
+                } while (!rcu_dereference_raw(rt_hash_table[st->bucket].chain));
                 rcu_read_lock_bh();
-                r = rt_hash_table[st->bucket].chain;
+                r = rcu_dereference_bh(rt_hash_table[st->bucket].chain);
         }
-        return rcu_dereference_bh(r);
+        return r;
 }
 
 static struct rtable *rt_cache_get_next(struct seq_file *seq,
@@ -721,19 +721,23 @@ static void rt_do_flush(int process_context)
         for (i = 0; i <= rt_hash_mask; i++) {
                 if (process_context && need_resched())
                         cond_resched();
-                rth = rt_hash_table[i].chain;
+                rth = rcu_dereference_raw(rt_hash_table[i].chain);
                 if (!rth)
                         continue;
 
                 spin_lock_bh(rt_hash_lock_addr(i));
 #ifdef CONFIG_NET_NS
                 {
-                struct rtable ** prev, * p;
+                struct rtable __rcu **prev;
+                struct rtable *p;
 
-                rth = rt_hash_table[i].chain;
+                rth = rcu_dereference_protected(rt_hash_table[i].chain,
+                        lockdep_is_held(rt_hash_lock_addr(i)));
 
                 /* defer releasing the head of the list after spin_unlock */
-                for (tail = rth; tail; tail = tail->dst.rt_next)
+                for (tail = rth; tail;
+                     tail = rcu_dereference_protected(tail->dst.rt_next,
+                                lockdep_is_held(rt_hash_lock_addr(i))))
                         if (!rt_is_expired(tail))
                                 break;
                 if (rth != tail)
@@ -741,8 +745,12 @@ static void rt_do_flush(int process_context)
 
                 /* call rt_free on entries after the tail requiring flush */
                 prev = &rt_hash_table[i].chain;
-                for (p = *prev; p; p = next) {
-                        next = p->dst.rt_next;
+                for (p = rcu_dereference_protected(*prev,
+                                lockdep_is_held(rt_hash_lock_addr(i)));
+                     p != NULL;
+                     p = next) {
+                        next = rcu_dereference_protected(p->dst.rt_next,
+                                lockdep_is_held(rt_hash_lock_addr(i)));
                         if (!rt_is_expired(p)) {
                                 prev = &p->dst.rt_next;
                         } else {
@@ -752,14 +760,15 @@ static void rt_do_flush(int process_context)
                 }
                 }
 #else
-                rth = rt_hash_table[i].chain;
-                rt_hash_table[i].chain = NULL;
+                rth = rcu_dereference_protected(rt_hash_table[i].chain,
+                        lockdep_is_held(rt_hash_lock_addr(i)));
+                rcu_assign_pointer(rt_hash_table[i].chain, NULL);
                 tail = NULL;
 #endif
                 spin_unlock_bh(rt_hash_lock_addr(i));
 
                 for (; rth != tail; rth = next) {
-                        next = rth->dst.rt_next;
+                        next = rcu_dereference_protected(rth->dst.rt_next, 1);
                         rt_free(rth);
                 }
         }
@@ -790,7 +799,7 @@ static int has_noalias(const struct rtable *head, const struct rtable *rth)
         while (aux != rth) {
                 if (compare_hash_inputs(&aux->fl, &rth->fl))
                         return 0;
-                aux = aux->dst.rt_next;
+                aux = rcu_dereference_protected(aux->dst.rt_next, 1);
         }
         return ONE;
 }
@@ -799,7 +808,8 @@ static void rt_check_expire(void)
 {
         static unsigned int rover;
         unsigned int i = rover, goal;
-        struct rtable *rth, **rthp;
+        struct rtable *rth;
+        struct rtable __rcu **rthp;
         unsigned long samples = 0;
         unsigned long sum = 0, sum2 = 0;
         unsigned long delta;
@@ -825,11 +835,12 @@ static void rt_check_expire(void)
 
                 samples++;
 
-                if (*rthp == NULL)
+                if (rcu_dereference_raw(*rthp) == NULL)
                         continue;
                 length = 0;
                 spin_lock_bh(rt_hash_lock_addr(i));
-                while ((rth = *rthp) != NULL) {
+                while ((rth = rcu_dereference_protected(*rthp,
+                                        lockdep_is_held(rt_hash_lock_addr(i)))) != NULL) {
                         prefetch(rth->dst.rt_next);
                         if (rt_is_expired(rth)) {
                                 *rthp = rth->dst.rt_next;
@@ -941,7 +952,8 @@ static int rt_garbage_collect(struct dst_ops *ops)
         static unsigned long last_gc;
         static int rover;
         static int equilibrium;
-        struct rtable *rth, **rthp;
+        struct rtable *rth;
+        struct rtable __rcu **rthp;
         unsigned long now = jiffies;
         int goal;
         int entries = dst_entries_get_fast(&ipv4_dst_ops);
@@ -995,7 +1007,8 @@ static int rt_garbage_collect(struct dst_ops *ops)
                         k = (k + 1) & rt_hash_mask;
                         rthp = &rt_hash_table[k].chain;
                         spin_lock_bh(rt_hash_lock_addr(k));
-                        while ((rth = *rthp) != NULL) {
+                        while ((rth = rcu_dereference_protected(*rthp,
+                                        lockdep_is_held(rt_hash_lock_addr(k)))) != NULL) {
                                 if (!rt_is_expired(rth) &&
                                         !rt_may_expire(rth, tmo, expire)) {
                                         tmo >>= 1;
@@ -1071,7 +1084,7 @@ static int slow_chain_length(const struct rtable *head)
 
         while (rth) {
                 length += has_noalias(head, rth);
-                rth = rth->dst.rt_next;
+                rth = rcu_dereference_protected(rth->dst.rt_next, 1);
         }
         return length >> FRACT_BITS;
 }
@@ -1079,9 +1092,9 @@ static int slow_chain_length(const struct rtable *head)
 static int rt_intern_hash(unsigned hash, struct rtable *rt,
                           struct rtable **rp, struct sk_buff *skb, int ifindex)
 {
-        struct rtable   *rth, **rthp;
+        struct rtable   *rth, *cand;
+        struct rtable __rcu **rthp, **candp;
         unsigned long   now;
-        struct rtable *cand, **candp;
         u32             min_score;
         int             chain_length;
         int attempts = !in_softirq();
@@ -1128,7 +1141,8 @@ restart:
         rthp = &rt_hash_table[hash].chain;
 
         spin_lock_bh(rt_hash_lock_addr(hash));
-        while ((rth = *rthp) != NULL) {
+        while ((rth = rcu_dereference_protected(*rthp,
+                        lockdep_is_held(rt_hash_lock_addr(hash)))) != NULL) {
                 if (rt_is_expired(rth)) {
                         *rthp = rth->dst.rt_next;
                         rt_free(rth);
@@ -1324,12 +1338,14 @@ EXPORT_SYMBOL(__ip_select_ident);
 
 static void rt_del(unsigned hash, struct rtable *rt)
 {
-        struct rtable **rthp, *aux;
+        struct rtable __rcu **rthp;
+        struct rtable *aux;
 
         rthp = &rt_hash_table[hash].chain;
         spin_lock_bh(rt_hash_lock_addr(hash));
         ip_rt_put(rt);
-        while ((aux = *rthp) != NULL) {
+        while ((aux = rcu_dereference_protected(*rthp,
+                        lockdep_is_held(rt_hash_lock_addr(hash)))) != NULL) {
                 if (aux == rt || rt_is_expired(aux)) {
                         *rthp = aux->dst.rt_next;
                         rt_free(aux);
@@ -1346,7 +1362,8 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
 {
         int i, k;
         struct in_device *in_dev = __in_dev_get_rcu(dev);
-        struct rtable *rth, **rthp;
+        struct rtable *rth;
+        struct rtable __rcu **rthp;
         __be32  skeys[2] = { saddr, 0 };
         int  ikeys[2] = { dev->ifindex, 0 };
         struct netevent_redirect netevent;
@@ -1379,7 +1396,7 @@ void ip_rt_redirect(__be32 old_gw, __be32 daddr, __be32 new_gw,
                         unsigned hash = rt_hash(daddr, skeys[i], ikeys[k],
                                                 rt_genid(net));
 
-                        rthp=&rt_hash_table[hash].chain;
+                        rthp = &rt_hash_table[hash].chain;
 
                         while ((rth = rcu_dereference(*rthp)) != NULL) {
                                 struct rtable *rt;