From: Jason Wang Date: Wed, 2 May 2012 11:41:30 +0800 Subject: [1/5] 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 Signed-off-by: Michael S. Tsirkin --- 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;