flow: virtualize flow cache entry methods

This allows to validate the cached object before returning it.
It also allows to destruct object properly, if the last reference
was held in flow cache. This is also a prepartion for caching
bundles in the flow cache.

In return for virtualizing the methods, we save on:
- not having to regenerate the whole flow cache on policy removal:
  each flow matching a killed policy gets refreshed as the getter
  function notices it smartly.
- we do not have to call flow_cache_flush from policy gc, since the
  flow cache now properly deletes the object if it had any references

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 68 insertions, 60 deletions

diff --git a/net/core/flow.c b/net/core/flow.c
index 1d27ca6b421..521df52a77d 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -26,17 +26,16 @@
 #include <linux/security.h>
 
 struct flow_cache_entry {
-        struct flow_cache_entry *next;
-        u16                     family;
-        u8                      dir;
-        u32                     genid;
-        struct flowi            key;
-        void                    *object;
-        atomic_t                *object_ref;
+        struct flow_cache_entry         *next;
+        u16                             family;
+        u8                              dir;
+        u32                             genid;
+        struct flowi                    key;
+        struct flow_cache_object        *object;
 };
 
 struct flow_cache_percpu {
-        struct flow_cache_entry **      hash_table;
+        struct flow_cache_entry         **hash_table;
         int                             hash_count;
         u32                             hash_rnd;
         int                             hash_rnd_recalc;
@@ -44,7 +43,7 @@ struct flow_cache_percpu {
 };
 
 struct flow_flush_info {
-        struct flow_cache *             cache;
+        struct flow_cache               *cache;
         atomic_t                        cpuleft;
         struct completion               completion;
 };
@@ -52,7 +51,7 @@ struct flow_flush_info {
 struct flow_cache {
         u32                             hash_shift;
         unsigned long                   order;
-        struct flow_cache_percpu *      percpu;
+        struct flow_cache_percpu        *percpu;
         struct notifier_block           hotcpu_notifier;
         int                             low_watermark;
         int                             high_watermark;
@@ -78,12 +77,21 @@ static void flow_cache_new_hashrnd(unsigned long arg)
         add_timer(&fc->rnd_timer);
 }
 
+static int flow_entry_valid(struct flow_cache_entry *fle)
+{
+        if (atomic_read(&flow_cache_genid) != fle->genid)
+                return 0;
+        if (fle->object && !fle->object->ops->check(fle->object))
+                return 0;
+        return 1;
+}
+
 static void flow_entry_kill(struct flow_cache *fc,
                             struct flow_cache_percpu *fcp,
                             struct flow_cache_entry *fle)
 {
         if (fle->object)
-                atomic_dec(fle->object_ref);
+                fle->object->ops->delete(fle->object);
         kmem_cache_free(flow_cachep, fle);
         fcp->hash_count--;
 }
@@ -96,16 +104,18 @@ static void __flow_cache_shrink(struct flow_cache *fc,
         int i;
 
         for (i = 0; i < flow_cache_hash_size(fc); i++) {
-                int k = 0;
+                int saved = 0;
 
                 flp = &fcp->hash_table[i];
-                while ((fle = *flp) != NULL && k < shrink_to) {
-                        k++;
-                        flp = &fle->next;
-                }
                 while ((fle = *flp) != NULL) {
-                        *flp = fle->next;
-                        flow_entry_kill(fc, fcp, fle);
+                        if (saved < shrink_to &&
+                            flow_entry_valid(fle)) {
+                                saved++;
+                                flp = &fle->next;
+                        } else {
+                                *flp = fle->next;
+                                flow_entry_kill(fc, fcp, fle);
+                        }
                 }
         }
 }
@@ -166,18 +176,21 @@ static int flow_key_compare(struct flowi *key1, struct flowi *key2)
         return 0;
 }
 
-void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
-                        flow_resolve_t resolver)
+struct flow_cache_object *
+flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
+                  flow_resolve_t resolver, void *ctx)
 {
         struct flow_cache *fc = &flow_cache_global;
         struct flow_cache_percpu *fcp;
         struct flow_cache_entry *fle, **head;
+        struct flow_cache_object *flo;
         unsigned int hash;
 
         local_bh_disable();
         fcp = per_cpu_ptr(fc->percpu, smp_processor_id());
 
         fle = NULL;
+        flo = NULL;
         /* Packet really early in init?  Making flow_cache_init a
          * pre-smp initcall would solve this.  --RR */
         if (!fcp->hash_table)
@@ -185,27 +198,17 @@ void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
 
         if (fcp->hash_rnd_recalc)
                 flow_new_hash_rnd(fc, fcp);
-        hash = flow_hash_code(fc, fcp, key);
 
+        hash = flow_hash_code(fc, fcp, key);
         head = &fcp->hash_table[hash];
         for (fle = *head; fle; fle = fle->next) {
                 if (fle->family == family &&
                     fle->dir == dir &&
-                    flow_key_compare(key, &fle->key) == 0) {
-                        if (fle->genid == atomic_read(&flow_cache_genid)) {
-                                void *ret = fle->object;
-
-                                if (ret)
-                                        atomic_inc(fle->object_ref);
-                                local_bh_enable();
-
-                                return ret;
-                        }
+                    flow_key_compare(key, &fle->key) == 0)
                         break;
-                }
         }
 
-        if (!fle) {
+        if (unlikely(!fle)) {
                 if (fcp->hash_count > fc->high_watermark)
                         flow_cache_shrink(fc, fcp);
 
@@ -219,33 +222,39 @@ void *flow_cache_lookup(struct net *net, struct flowi *key, u16 family, u8 dir,
                         fle->object = NULL;
                         fcp->hash_count++;
                 }
+        } else if (likely(fle->genid == atomic_read(&flow_cache_genid))) {
+                flo = fle->object;
+                if (!flo)
+                        goto ret_object;
+                flo = flo->ops->get(flo);
+                if (flo)
+                        goto ret_object;
+        } else if (fle->object) {
+                flo = fle->object;
+                flo->ops->delete(flo);
+                fle->object = NULL;
         }
 
 nocache:
-        {
-                int err;
-                void *obj;
-                atomic_t *obj_ref;
-
-                err = resolver(net, key, family, dir, &obj, &obj_ref);
-
-                if (fle && !err) {
-                        fle->genid = atomic_read(&flow_cache_genid);
-
-                        if (fle->object)
-                                atomic_dec(fle->object_ref);
-
-                        fle->object = obj;
-                        fle->object_ref = obj_ref;
-                        if (obj)
-                                atomic_inc(fle->object_ref);
-                }
-                local_bh_enable();
-
-                if (err)
-                        obj = ERR_PTR(err);
-                return obj;
+        flo = NULL;
+        if (fle) {
+                flo = fle->object;
+                fle->object = NULL;
+        }
+        flo = resolver(net, key, family, dir, flo, ctx);
+        if (fle) {
+                fle->genid = atomic_read(&flow_cache_genid);
+                if (!IS_ERR(flo))
+                        fle->object = flo;
+                else
+                        fle->genid--;
+        } else {
+                if (flo && !IS_ERR(flo))
+                        flo->ops->delete(flo);
         }
+ret_object:
+        local_bh_enable();
+        return flo;
 }
 
 static void flow_cache_flush_tasklet(unsigned long data)
@@ -261,13 +270,12 @@ static void flow_cache_flush_tasklet(unsigned long data)
 
                 fle = fcp->hash_table[i];
                 for (; fle; fle = fle->next) {
-                        unsigned genid = atomic_read(&flow_cache_genid);
-
-                        if (!fle->object || fle->genid == genid)
+                        if (flow_entry_valid(fle))
                                 continue;
 
+                        if (fle->object)
+                                fle->object->ops->delete(fle->object);
                         fle->object = NULL;
-                        atomic_dec(fle->object_ref);
                 }
         }