diff mbox

[02/11] net: add function to allocate skbuff head without data area

Message ID 1315070771-18576-3-git-send-email-kaber@trash.net
State RFC, archived
Delegated to: David Miller
Headers show

Commit Message

Patrick McHardy Sept. 3, 2011, 5:26 p.m. UTC 
From: Patrick McHardy <kaber@trash.net>

Add a function to allocate a skbuff head without any data. This will be
used by memory mapped netlink to attach data from the mmaped area to the
skb.

Additionally change skb_release_all() to check whether the skb has a
data area to allow the skb destructor to clear the data pointer in
case only a head has been allocated.

Signed-off-by: Patrick McHardy <kaber@trash.net>
---
 include/linux/skbuff.h |    6 ++++++
 net/core/skbuff.c      |   31 ++++++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 1 deletions(-)

Comments

Eric Dumazet Sept. 4, 2011, 8:12 a.m. UTC | #1 
Le samedi 03 septembre 2011 à 19:26 +0200, kaber@trash.net a écrit :

> +struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
> +{
> +	struct sk_buff *skb;
> +
> +	/* Get the HEAD */
> +	skb = kmem_cache_alloc_node(skbuff_head_cache,
> +				    gfp_mask & ~__GFP_DMA, node);
> +	if (!skb)
> +		goto out;
> +	prefetchw(skb);

Please remove this prefetchw(), since we have no delay between it and
actual memset(skb).

> +
> +	/*
> +	 * Only clear those fields we need to clear, not those that we will
> +	 * actually initialise below. Hence, don't put any more fields after
> +	 * the tail pointer in struct sk_buff!
> +	 */
> +	memset(skb, 0, offsetof(struct sk_buff, tail));



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Patrick McHardy Sept. 7, 2011, 3:20 p.m. UTC | #2 
On 04.09.2011 10:12, Eric Dumazet wrote:
> Le samedi 03 septembre 2011 à 19:26 +0200, kaber@trash.net a écrit :
> 
>> +struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
>> +{
>> +	struct sk_buff *skb;
>> +
>> +	/* Get the HEAD */
>> +	skb = kmem_cache_alloc_node(skbuff_head_cache,
>> +				    gfp_mask & ~__GFP_DMA, node);
>> +	if (!skb)
>> +		goto out;
>> +	prefetchw(skb);
> 
> Please remove this prefetchw(), since we have no delay between it and
> actual memset(skb).

Done, thanks.
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diff mbox

Patch

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 7b996ed..8cfc285 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -521,6 +521,12 @@  static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
 	return __alloc_skb(size, priority, 1, NUMA_NO_NODE);
 }
 
+extern struct sk_buff *__alloc_skb_head(gfp_t priority, int node);
+static inline struct sk_buff *alloc_skb_head(gfp_t priority)
+{
+	return __alloc_skb_head(priority, -1);
+}
+
 extern bool skb_recycle_check(struct sk_buff *skb, int skb_size);
 
 extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2beda82..d632de9 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -153,6 +153,34 @@  static void skb_under_panic(struct sk_buff *skb, int sz, void *here)
  *
  */
 
+struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
+{
+	struct sk_buff *skb;
+
+	/* Get the HEAD */
+	skb = kmem_cache_alloc_node(skbuff_head_cache,
+				    gfp_mask & ~__GFP_DMA, node);
+	if (!skb)
+		goto out;
+	prefetchw(skb);
+
+	/*
+	 * Only clear those fields we need to clear, not those that we will
+	 * actually initialise below. Hence, don't put any more fields after
+	 * the tail pointer in struct sk_buff!
+	 */
+	memset(skb, 0, offsetof(struct sk_buff, tail));
+	skb->data = NULL;
+	skb->truesize = sizeof(struct sk_buff);
+	atomic_set(&skb->users, 1);
+
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+	skb->mac_header = ~0U;
+#endif
+out:
+	return skb;
+}
+
 /**
  *	__alloc_skb	-	allocate a network buffer
  *	@size: size to allocate
@@ -414,7 +442,8 @@  static void skb_release_head_state(struct sk_buff *skb)
 static void skb_release_all(struct sk_buff *skb)
 {
 	skb_release_head_state(skb);
-	skb_release_data(skb);
+	if (likely(skb->data))
+		skb_release_data(skb);
 }
 
 /**