net: use skb_copy_datagram_from_iovec() in zerocopy_sg_from_iovec()

Use skb_copy_datagram_from_iovec() to avoid code duplication and make it easy to
be read. Also we can do the skipping inside the zero-copy loop.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 27 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
index badcd93e5dd8..af814e764206 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -591,48 +591,31 @@ int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
                                   int offset, size_t count)
 {
         int len = iov_length(from, count) - offset;
-        int copy = skb_headlen(skb);
-        int size, offset1 = 0;
+        int copy = min_t(int, skb_headlen(skb), len);
+        int size;
         int i = 0;
 
-        /* Skip over from offset */
-        while (count && (offset >= from->iov_len)) {
-                offset -= from->iov_len;
-                ++from;
-                --count;
-        }
-
         /* copy up to skb headlen */
-        while (count && (copy > 0)) {
-                size = min_t(unsigned int, copy, from->iov_len - offset);
-                if (copy_from_user(skb->data + offset1, from->iov_base + offset,
-                                   size))
-                        return -EFAULT;
-                if (copy > size) {
-                        ++from;
-                        --count;
-                        offset = 0;
-                } else
-                        offset += size;
-                copy -= size;
-                offset1 += size;
-        }
+        if (skb_copy_datagram_from_iovec(skb, 0, from, offset, copy))
+                return -EFAULT;
 
-        if (len == offset1)
+        if (len == copy)
                 return 0;
 
+        offset += copy;
         while (count--) {
                 struct page *page[MAX_SKB_FRAGS];
                 int num_pages;
                 unsigned long base;
                 unsigned long truesize;
 
-                len = from->iov_len - offset;
-                if (!len) {
-                        offset = 0;
+                /* Skip over from offset and copied */
+                if (offset >= from->iov_len) {
+                        offset -= from->iov_len;
                         ++from;
                         continue;
                 }
+                len = from->iov_len - offset;
                 base = (unsigned long)from->iov_base + offset;
                 size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
                 if (i + size > MAX_SKB_FRAGS)