4 files changed, 47 insertions, 28 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 262efdbc346b..d8f7d74d5a4d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -781,6 +781,31 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len,
                                      int *errcode,
                                      gfp_t gfp_mask);
 
+/* Layout of fast clones : [skb1][skb2][fclone_ref] */
+struct sk_buff_fclones {
+        struct sk_buff  skb1;
+
+        struct sk_buff  skb2;
+
+        atomic_t        fclone_ref;
+};
+
+/**
+ *      skb_fclone_busy - check if fclone is busy
+ *      @skb: buffer
+ *
+ * Returns true is skb is a fast clone, and its clone is not freed.
+ */
+static inline bool skb_fclone_busy(const struct sk_buff *skb)
+{
+        const struct sk_buff_fclones *fclones;
+
+        fclones = container_of(skb, struct sk_buff_fclones, skb1);
+
+        return skb->fclone == SKB_FCLONE_ORIG &&
+               fclones->skb2.fclone == SKB_FCLONE_CLONE;
+}
+
 static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
                                                gfp_t priority)
 {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4be570a4ab21..a8cebb40699c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -257,15 +257,16 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
         kmemcheck_annotate_variable(shinfo->destructor_arg);
 
         if (flags & SKB_ALLOC_FCLONE) {
-                struct sk_buff *child = skb + 1;
-                atomic_t *fclone_ref = (atomic_t *) (child + 1);
+                struct sk_buff_fclones *fclones;
 
-                kmemcheck_annotate_bitfield(child, flags1);
+                fclones = container_of(skb, struct sk_buff_fclones, skb1);
+
+                kmemcheck_annotate_bitfield(&fclones->skb2, flags1);
                 skb->fclone = SKB_FCLONE_ORIG;
-                atomic_set(fclone_ref, 1);
+                atomic_set(&fclones->fclone_ref, 1);
 
-                child->fclone = SKB_FCLONE_UNAVAILABLE;
-                child->pfmemalloc = pfmemalloc;
+                fclones->skb2.fclone = SKB_FCLONE_UNAVAILABLE;
+                fclones->skb2.pfmemalloc = pfmemalloc;
         }
 out:
         return skb;
@@ -524,8 +525,7 @@ static void skb_release_data(struct sk_buff *skb)
  */
 static void kfree_skbmem(struct sk_buff *skb)
 {
-        struct sk_buff *other;
-        atomic_t *fclone_ref;
+        struct sk_buff_fclones *fclones;
 
         switch (skb->fclone) {
         case SKB_FCLONE_UNAVAILABLE:
@@ -533,22 +533,21 @@ static void kfree_skbmem(struct sk_buff *skb)
                 break;
 
         case SKB_FCLONE_ORIG:
-                fclone_ref = (atomic_t *) (skb + 2);
-                if (atomic_dec_and_test(fclone_ref))
-                        kmem_cache_free(skbuff_fclone_cache, skb);
+                fclones = container_of(skb, struct sk_buff_fclones, skb1);
+                if (atomic_dec_and_test(&fclones->fclone_ref))
+                        kmem_cache_free(skbuff_fclone_cache, fclones);
                 break;
 
         case SKB_FCLONE_CLONE:
-                fclone_ref = (atomic_t *) (skb + 1);
-                other = skb - 1;
+                fclones = container_of(skb, struct sk_buff_fclones, skb2);
 
                 /* The clone portion is available for
                  * fast-cloning again.
                  */
                 skb->fclone = SKB_FCLONE_UNAVAILABLE;
 
-                if (atomic_dec_and_test(fclone_ref))
-                        kmem_cache_free(skbuff_fclone_cache, other);
+                if (atomic_dec_and_test(&fclones->fclone_ref))
+                        kmem_cache_free(skbuff_fclone_cache, fclones);
                 break;
         }
 }
@@ -859,17 +858,18 @@ EXPORT_SYMBOL_GPL(skb_copy_ubufs);
 
 struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 {
-        struct sk_buff *n;
+        struct sk_buff_fclones *fclones = container_of(skb,
+                                                       struct sk_buff_fclones,
+                                                       skb1);
+        struct sk_buff *n = &fclones->skb2;
 
         if (skb_orphan_frags(skb, gfp_mask))
                 return NULL;
 
-        n = skb + 1;
         if (skb->fclone == SKB_FCLONE_ORIG &&
             n->fclone == SKB_FCLONE_UNAVAILABLE) {
-                atomic_t *fclone_ref = (atomic_t *) (n + 1);
                 n->fclone = SKB_FCLONE_CLONE;
-                atomic_inc(fclone_ref);
+                atomic_inc(&fclones->fclone_ref);
         } else {
                 if (skb_pfmemalloc(skb))
                         gfp_mask |= __GFP_MEMALLOC;
@@ -3240,8 +3240,7 @@ void __init skb_init(void)
                                               SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                                               NULL);
         skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
-                                                (2*sizeof(struct sk_buff)) +
-                                                sizeof(atomic_t),
+                                                sizeof(struct sk_buff_fclones),
                                                 0,
                                                 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
                                                 NULL);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ee567e9e98c3..8d4eac793700 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2110,10 +2110,7 @@ bool tcp_schedule_loss_probe(struct sock *sk)
 static bool skb_still_in_host_queue(const struct sock *sk,
                                     const struct sk_buff *skb)
 {
-        const struct sk_buff *fclone = skb + 1;
-
-        if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
-                     fclone->fclone == SKB_FCLONE_CLONE)) {
+        if (unlikely(skb_fclone_busy(skb))) {
                 NET_INC_STATS_BH(sock_net(sk),
                                  LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
                 return true;
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index f623dca6ce30..4c4e457e7888 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1961,10 +1961,8 @@ static int xdst_queue_output(struct sock *sk, struct sk_buff *skb)
         struct xfrm_dst *xdst = (struct xfrm_dst *) dst;
         struct xfrm_policy *pol = xdst->pols[0];
         struct xfrm_policy_queue *pq = &pol->polq;
-        const struct sk_buff *fclone = skb + 1;
 
-        if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
-                     fclone->fclone == SKB_FCLONE_CLONE)) {
+        if (unlikely(skb_fclone_busy(skb))) {
                 kfree_skb(skb);
                 return 0;
         }