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Subject[PATCH v2 07/17] new helpers: skb_copy_datagram_from_iter() and zerocopy_sg_from_iter()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
include/linux/skbuff.h | 3 ++
net/core/datagram.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 119 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index d048347..a01cd9a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2659,10 +2659,13 @@ static inline int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, int hlen,
int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
const struct iovec *from, int from_offset,
int len);
+int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
+ struct iov_iter *from, int len);
int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *frm,
int offset, size_t count);
int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
struct iov_iter *to, int size);
+int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *frm);
void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb);
int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 26391a3..3ea0384 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -572,6 +572,78 @@ fault:
}
EXPORT_SYMBOL(skb_copy_datagram_from_iovec);

+int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
+ struct iov_iter *from,
+ int len)
+{
+ int start = skb_headlen(skb);
+ int i, copy = start - offset;
+ struct sk_buff *frag_iter;
+
+ /* Copy header. */
+ if (copy > 0) {
+ if (copy > len)
+ copy = len;
+ if (copy_from_iter(skb->data + offset, copy, from) != copy)
+ goto fault;
+ if ((len -= copy) == 0)
+ return 0;
+ offset += copy;
+ }
+
+ /* Copy paged appendix. Hmm... why does this look so complicated? */
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ int end;
+ const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+ WARN_ON(start > offset + len);
+
+ end = start + skb_frag_size(frag);
+ if ((copy = end - offset) > 0) {
+ size_t copied;
+
+ if (copy > len)
+ copy = len;
+ copied = copy_page_from_iter(skb_frag_page(frag),
+ frag->page_offset + offset - start,
+ copy, from);
+ if (copied != copy)
+ goto fault;
+
+ if (!(len -= copy))
+ return 0;
+ offset += copy;
+ }
+ start = end;
+ }
+
+ skb_walk_frags(skb, frag_iter) {
+ int end;
+
+ WARN_ON(start > offset + len);
+
+ end = start + frag_iter->len;
+ if ((copy = end - offset) > 0) {
+ if (copy > len)
+ copy = len;
+ if (skb_copy_datagram_from_iter(frag_iter,
+ offset - start,
+ from, copy))
+ goto fault;
+ if ((len -= copy) == 0)
+ return 0;
+ offset += copy;
+ }
+ start = end;
+ }
+ if (!len)
+ return 0;
+
+fault:
+ return -EFAULT;
+}
+EXPORT_SYMBOL(skb_copy_datagram_from_iter);
+
/**
* zerocopy_sg_from_iovec - Build a zerocopy datagram from an iovec
* @skb: buffer to copy
@@ -643,6 +715,50 @@ int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
}
EXPORT_SYMBOL(zerocopy_sg_from_iovec);

+int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
+{
+ int len = iov_iter_count(from);
+ int copy = min_t(int, skb_headlen(skb), len);
+ int frag = 0;
+
+ /* copy up to skb headlen */
+ if (skb_copy_datagram_from_iter(skb, 0, from, copy))
+ return -EFAULT;
+
+ while (iov_iter_count(from)) {
+ struct page *pages[MAX_SKB_FRAGS];
+ size_t start;
+ ssize_t copied;
+ unsigned long truesize;
+ int n = 0;
+
+ if (frag == MAX_SKB_FRAGS)
+ return -EMSGSIZE;
+
+ copied = iov_iter_get_pages(from, pages, ~0U,
+ MAX_SKB_FRAGS - frag, &start);
+ if (copied < 0)
+ return -EFAULT;
+
+ iov_iter_advance(from, copied);
+
+ truesize = PAGE_ALIGN(copied + start);
+ skb->data_len += copied;
+ skb->len += copied;
+ skb->truesize += truesize;
+ atomic_add(truesize, &skb->sk->sk_wmem_alloc);
+ while (copied) {
+ int size = min_t(int, copied, PAGE_SIZE - start);
+ skb_fill_page_desc(skb, frag++, pages[n], start, size);
+ start = 0;
+ copied -= size;
+ n++;
+ }
+ }
+ return 0;
+}
+EXPORT_SYMBOL(zerocopy_sg_from_iter);
+
static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
u8 __user *to, int len,
__wsum *csump)
--
1.7.10.4


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