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/drivers/net/macvtap.c b/drivers/net/macvtap.c
index dfec20d..182364a 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -536,86 +536,6 @@ static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
        return skb;
 }
 
-/* set skb frags from iovec, this can move to core network code for reuse */
-static 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;
-}
-
 /*
  * macvtap_skb_from_vnet_hdr and macvtap_skb_to_vnet_hdr should
  * be shared with the tun/tap driver.

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 18527ef..b163047 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -961,86 +961,6 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
        return skb;
 }
 
-/* set skb frags from iovec, this can move to core network code for reuse */
-static 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;
-}
-
 /* Get packet from user space buffer */
 static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                            void *msg_control, const struct iovec *iv,

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ae46475..5ac96f3 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2359,6 +2359,10 @@ extern int              skb_copy_datagram_from_iovec(struct sk_buff *skb,
                                                    const struct iovec *from,
                                                    int from_offset,
                                                    int len);
+extern int            zerocopy_sg_from_iovec(struct sk_buff *skb,
+                                             const struct iovec *frm,
+                                             int offset,
+                                             size_t count);
 extern int            skb_copy_datagram_const_iovec(const struct sk_buff *from,
                                                     int offset,
                                                     const struct iovec *to,

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 8ab48cd..f987fae 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -573,6 +573,99 @@ fault:
 }
 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)