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Subject[RFC v2 03/19] net: add zerocopy_sg_from_iter for bvec
Date
Add a separate path for bvec iterators in __zerocopy_sg_from_iter, first
it's quite faster but also will be needed to optimise out
get/put_page()

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
net/core/datagram.c | 50 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)

diff --git a/net/core/datagram.c b/net/core/datagram.c
index ee290776c661..cb1e34fbcd44 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -616,11 +616,61 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
}
EXPORT_SYMBOL(skb_copy_datagram_from_iter);

+static int __zerocopy_sg_from_bvec(struct sock *sk, struct sk_buff *skb,
+ struct iov_iter *from, size_t length)
+{
+ int ret, frag = skb_shinfo(skb)->nr_frags;
+ struct bvec_iter bi;
+ struct bio_vec v;
+ ssize_t copied = 0;
+ unsigned long truesize = 0;
+
+ bi.bi_size = min(from->count, length);
+ bi.bi_bvec_done = from->iov_offset;
+ bi.bi_idx = 0;
+
+ while (bi.bi_size) {
+ if (frag == MAX_SKB_FRAGS) {
+ ret = -EMSGSIZE;
+ goto out;
+ }
+
+ v = mp_bvec_iter_bvec(from->bvec, bi);
+ copied += v.bv_len;
+ truesize += PAGE_ALIGN(v.bv_len + v.bv_offset);
+ get_page(v.bv_page);
+ skb_fill_page_desc(skb, frag++, v.bv_page, v.bv_offset, v.bv_len);
+ bvec_iter_advance_single(from->bvec, &bi, v.bv_len);
+ }
+ ret = 0;
+out:
+ skb->data_len += copied;
+ skb->len += copied;
+ skb->truesize += truesize;
+
+ if (sk && sk->sk_type == SOCK_STREAM) {
+ sk_wmem_queued_add(sk, truesize);
+ if (!skb_zcopy_pure(skb))
+ sk_mem_charge(sk, truesize);
+ } else {
+ refcount_add(truesize, &skb->sk->sk_wmem_alloc);
+ }
+
+ from->bvec += bi.bi_idx;
+ from->nr_segs -= bi.bi_idx;
+ from->count = bi.bi_size;
+ from->iov_offset = bi.bi_bvec_done;
+ return ret;
+}
+
int __zerocopy_sg_from_iter(struct sock *sk, struct sk_buff *skb,
struct iov_iter *from, size_t length)
{
int frag = skb_shinfo(skb)->nr_frags;

+ if (iov_iter_is_bvec(from))
+ return __zerocopy_sg_from_bvec(sk, skb, from, length);
+
while (length && iov_iter_count(from)) {
struct page *pages[MAX_SKB_FRAGS];
struct page *last_head = NULL;
--
2.34.1
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