[V2,1/9] macvtap: zerocopy: fix offset calculation when building skb
diff mbox series

Message ID 20120502034130.11782.25906.stgit@amd-6168-8-1.englab.nay.redhat.com
State New, archived
Headers show
Series
  • vhost/macvtap zeropcopy fixes
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Commit Message

Jason Wang May 2, 2012, 3:41 a.m. UTC
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>
---
 drivers/net/macvtap.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)


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Comments

Shirley Ma May 15, 2012, 5:17 p.m. UTC | #1
On Wed, 2012-05-02 at 11:41 +0800, Jason Wang wrote:
> 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

I tested the original code in all scenario, it worked well.

However this patch makes the code more clear.

Thanks
Shirley

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Patch
diff mbox series

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;