From: Jason Wang <jasowang@redhat.com>
Date: Wed, 2 May 2012 03:41:30 +0000 (+0800)
Subject: macvtap: zerocopy: fix offset calculation when building skb
X-Git-Tag: v3.2.24~93
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c1b5b21b540f22a8e008d30545c044a6c949b47b;p=thirdparty%2Fkernel%2Fstable.git

macvtap: zerocopy: fix offset calculation when building skb

commit 3afc9621f15701c557e60f61eba9242bac2771dd upstream.

This patch fixes the offset calculation when building skb:

- offset1 were used as skb data offset not vector offset
- reset offset to zero only when we advance to next vector

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 1b7082d08f334..45050085c8ce0 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -504,10 +504,11 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		if (copy > size) {
 			++from;
 			--count;
-		}
+			offset = 0;
+		} else
+			offset += size;
 		copy -= size;
 		offset1 += size;
-		offset = 0;
 	}
 
 	if (len == offset1)
@@ -518,13 +519,13 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		int num_pages;
 		unsigned long base;
 
-		len = from->iov_len - offset1;
+		len = from->iov_len - offset;
 		if (!len) {
-			offset1 = 0;
+			offset = 0;
 			++from;
 			continue;
 		}
-		base = (unsigned long)from->iov_base + offset1;
+		base = (unsigned long)from->iov_base + offset;
 		size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
 		num_pages = get_user_pages_fast(base, size, 0, &page[i]);
 		if ((num_pages != size) ||
@@ -545,7 +546,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 			len -= size;
 			i++;
 		}
-		offset1 = 0;
+		offset = 0;
 		++from;
 	}
 	return 0;