[RFC][PATCH v6 11/19] Use callback to deal with skb_release_data() specially.

[xiaohui . xin]

From: Xin Xiaohui <xiaohui.xin@xxxxxxxxx>

If buffer is external, then use the callback to destruct
buffers.

Signed-off-by: Xin Xiaohui <xiaohui.xin@xxxxxxxxx>
Signed-off-by: Zhao Yu <yzhao81new@xxxxxxxxx>
Reviewed-by: Jeff Dike <jdike@xxxxxxxxxxxxxxx>
---
 net/core/skbuff.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 37587f0..418457c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -385,6 +385,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
 
 static void skb_release_data(struct sk_buff *skb)
 {
+	/* check if the skb has external buffers, we have use destructor_arg
+	 * here to indicate
+	 */
+	struct skb_external_page *ext_page = skb_shinfo(skb)->destructor_arg;
+
 	if (!skb->cloned ||
 	    !atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
 			       &skb_shinfo(skb)->dataref)) {
@@ -397,6 +402,12 @@ static void skb_release_data(struct sk_buff *skb)
 		if (skb_has_frags(skb))
 			skb_drop_fraglist(skb);
 
+		/* if the skb has external buffers, use destructor here,
+		 * since after that skb->head will be kfree, in case skb->head
+		 * from external buffer cannot use kfree to destroy.
+		 */
+		if (dev_is_mpassthru(skb->dev) && ext_page && ext_page->dtor)
+			ext_page->dtor(ext_page);
 		kfree(skb->head);
 	}
 }
-- 
1.5.4.4

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