1 files changed, 32 insertions, 7 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2beda824636e..387703f56fce 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -611,8 +611,21 @@ struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
 }
 EXPORT_SYMBOL_GPL(skb_morph);
 
-/* skb frags copy userspace buffers to kernel */
-static int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
+/*	skb_copy_ubufs	-	copy userspace skb frags buffers to kernel
+ *	@skb: the skb to modify
+ *	@gfp_mask: allocation priority
+ *
+ *	This must be called on SKBTX_DEV_ZEROCOPY skb.
+ *	It will copy all frags into kernel and drop the reference
+ *	to userspace pages.
+ *
+ *	If this function is called from an interrupt gfp_mask() must be
+ *	%GFP_ATOMIC.
+ *
+ *	Returns 0 on success or a negative error code on failure
+ *	to allocate kernel memory to copy to.
+ */
+int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
 {
 	int i;
 	int num_frags = skb_shinfo(skb)->nr_frags;
@@ -652,6 +665,8 @@ static int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask)
 		skb_shinfo(skb)->frags[i - 1].page = head;
 		head = (struct page *)head->private;
 	}
+
+	skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
 	return 0;
 }
 
@@ -677,7 +692,6 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 	if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) {
 		if (skb_copy_ubufs(skb, gfp_mask))
 			return NULL;
-		skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
 	}
 
 	n = skb + 1;
@@ -803,7 +817,6 @@ struct sk_buff *pskb_copy(struct sk_buff *skb, gfp_t gfp_mask)
 				n = NULL;
 				goto out;
 			}
-			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
 		}
 		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
 			skb_shinfo(n)->frags[i] = skb_shinfo(skb)->frags[i];
@@ -896,7 +909,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 		if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) {
 			if (skb_copy_ubufs(skb, gfp_mask))
 				goto nofrags;
-			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
 		}
 		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
 			get_page(skb_shinfo(skb)->frags[i].page);
@@ -1369,8 +1381,21 @@ pull_pages:
 }
 EXPORT_SYMBOL(__pskb_pull_tail);
 
-/* Copy some data bits from skb to kernel buffer. */
-
+/**
+ *	skb_copy_bits - copy bits from skb to kernel buffer
+ *	@skb: source skb
+ *	@offset: offset in source
+ *	@to: destination buffer
+ *	@len: number of bytes to copy
+ *
+ *	Copy the specified number of bytes from the source skb to the
+ *	destination buffer.
+ *
+ *	CAUTION ! :
+ *		If its prototype is ever changed,
+ *		check arch/{*}/net/{*}.S files,
+ *		since it is called from BPF assembly code.
+ */
 int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)
 {
 	int start = skb_headlen(skb);