net: move zerocopy_sg_from_iovec() to net/core/datagram.c
To let it be reused and reduce code duplication. Also document this function.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 8ab48cd..f987fae 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -573,6 +573,99 @@
}
EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
+/**
+ * zerocopy_sg_from_iovec - Build a zerocopy datagram from an iovec
+ * @skb: buffer to copy
+ * @from: io vector to copy to
+ * @offset: offset in the io vector to start copying from
+ * @count: amount of vectors to copy to buffer from
+ *
+ * The function will first copy up to headlen, and then pin the userspace
+ * pages and build frags through them.
+ *
+ * Returns 0, -EFAULT or -EMSGSIZE.
+ * Note: the iovec is not modified during the copy
+ */
+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 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 (len == offset1)
+ return 0;
+
+ 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;
+ ++from;
+ continue;
+ }
+ base = (unsigned long)from->iov_base + offset;
+ size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
+ if (i + size > MAX_SKB_FRAGS)
+ return -EMSGSIZE;
+ num_pages = get_user_pages_fast(base, size, 0, &page[i]);
+ if (num_pages != size) {
+ int j;
+
+ for (j = 0; j < num_pages; j++)
+ put_page(page[i + j]);
+ return -EFAULT;
+ }
+ truesize = size * PAGE_SIZE;
+ skb->data_len += len;
+ skb->len += len;
+ skb->truesize += truesize;
+ atomic_add(truesize, &skb->sk->sk_wmem_alloc);
+ while (len) {
+ int off = base & ~PAGE_MASK;
+ int size = min_t(int, len, PAGE_SIZE - off);
+ __skb_fill_page_desc(skb, i, page[i], off, size);
+ skb_shinfo(skb)->nr_frags++;
+ /* increase sk_wmem_alloc */
+ base += size;
+ len -= size;
+ i++;
+ }
+ offset = 0;
+ ++from;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(zerocopy_sg_from_iovec);
+
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
u8 __user *to, int len,
__wsum *csump)