diff options
Diffstat (limited to 'net/core/datagram.c')
| -rw-r--r-- | net/core/datagram.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/net/core/datagram.c b/net/core/datagram.c index 8ab48cd8955..af814e76420 100644 --- 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 +574,77 @@ 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 = min_t(int, skb_headlen(skb), len); + int size; + int i = 0; + + /* copy up to skb headlen */ + if (skb_copy_datagram_from_iovec(skb, 0, from, offset, copy)) + return -EFAULT; + + if (len == copy) + return 0; + + offset += copy; + while (count--) { + struct page *page[MAX_SKB_FRAGS]; + int num_pages; + unsigned long base; + unsigned long truesize; + + /* 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) + 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) |