net: cleanup and document skb fclone layout
Lets use a proper structure to clearly document and implement
skb fast clones.
Then, we might experiment more easily alternative layouts.
This patch adds a new skb_fclone_busy() helper, used by tcp and xfrm,
to stop leaking of implementation details.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4be570a..a8cebb4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -257,15 +257,16 @@
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 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 @@
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 @@
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 @@
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);