[ 016/108] macvtap: zerocopy: fix offset calculation when building skb

Ben Hutchings
2012-07-23T01:42:21Z

From: Jason Wang <jasowang@redhat.com>

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>
---
drivers/net/macvtap.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0427c65..bd4a70d 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -505,10 +505,11 @@ 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)
@@ -519,13 +520,13 @@ 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) ||
@@ -546,7 +547,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
len -= size;
i++;
}
- offset1 = 0;
+ offset = 0;
++from;
}
return 0;