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SubjectRe: [PATCH v15 00/17] Provide a zero-copy method on KVM virtio-net.
Date
From: Xin Xiaohui <xiaohui.xin@intel.com>

>2) The idea to key off of skb->dev in skb_release_data() is
> fundamentally flawed since many actions can change skb->dev on you,
> which will end up causing a leak of your external data areas.

How about this one? If the destructor_arg is not a good candidate,
then I have to add an apparent field in shinfo.

Thanks
Xiaohui

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 10ba67d..ad4636e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -199,14 +199,15 @@ struct skb_shared_info {
struct sk_buff *frag_list;
struct skb_shared_hwtstamps hwtstamps;

+ /* Intermediate layers must ensure that destructor_arg
+ * remains valid until skb destructor */
+ void * destructor_arg;
+
/*
* Warning : all fields before dataref are cleared in __alloc_skb()
*/
atomic_t dataref;

- /* Intermediate layers must ensure that destructor_arg
- * remains valid until skb destructor */
- void * destructor_arg;
/* must be last field, see pskb_expand_head() */
skb_frag_t frags[MAX_SKB_FRAGS];
};
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c83b421..eb040f4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -343,6 +343,13 @@ static void skb_release_data(struct sk_buff *skb)
if (skb_has_frags(skb))
skb_drop_fraglist(skb);

+ if (skb_shinfo(skb)->destructor_arg) {
+ struct skb_ext_page *ext_page =
+ skb_shinfo(skb)->destructor_arg;
+ if (ext_page->dtor)
+ ext_page->dtor(ext_page);
+ }
+
kfree(skb->head);
}
}
--
1.7.3


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