net: use release_pages() in zerocopy_sg_from_iovec()

[~andy/linux] / net / core / datagram.c

diff --git a/net/core/datagram.c b/net/core/datagram.c
index 8ab48cd8955971ec7db7e60464a946380a7be49a..badcd93e5dd8275391a609715feb7c0d2eab35f6 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -48,6 +48,7 @@
 #include <linux/highmem.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
+#include <linux/pagemap.h>
 
 #include <net/protocol.h>
 #include <linux/skbuff.h>
@@ -573,6 +574,94 @@ 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) {
+                       release_pages(&page[i], num_pages, 0);
+                       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);
+                       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)