linux-kernel - [ 017/108] macvtap: zerocopy: fix truesize underestimation

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Message-Id: <20120723010654.135814246@decadent.org.uk>
Date:	Mon, 23 Jul 2012 02:07:08 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jason Wang <jasowang@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: [ 017/108] macvtap: zerocopy: fix truesize underestimation

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@...hat.com>

commit 4ef67ebedffa44ed9939b34708ac2fee06d2f65f upstream.

As the skb fragment were pinned/built from user pages, we should
account the page instead of length for truesize.

Signed-off-by: Jason Wang <jasowang@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/macvtap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index bd4a70d..7cb2684 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -519,6 +519,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		struct page *page[MAX_SKB_FRAGS];
 		int num_pages;
 		unsigned long base;
+		unsigned long truesize;
 
 		len = from->iov_len - offset;
 		if (!len) {
@@ -533,10 +534,11 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		    (num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags))
 			/* put_page is in skb free */
 			return -EFAULT;
+		truesize = size * PAGE_SIZE;
 		skb->data_len += len;
 		skb->len += len;
-		skb->truesize += len;
-		atomic_add(len, &skb->sk->sk_wmem_alloc);
+		skb->truesize += truesize;
+		atomic_add(truesize, &skb->sk->sk_wmem_alloc);
 		while (len) {
 			int off = base & ~PAGE_MASK;
 			int size = min_t(int, len, PAGE_SIZE - off);



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