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Commit 55b07a65 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'net-zerocopy-refine' 



Willem de Bruijn says:

====================
zerocopy refinements

1/4 is a small optimization follow-up to the earlier fix to skb_segment:
    check skb state once per skb, instead of once per frag.
2/4 makes behavior more consistent between standard and zerocopy send:
    set the PSH bit when hitting MAX_SKB_FRAGS. This helps GRO.
3/4 resolves a surprising inconsistency in notification:
    because small packets were not stored in frags, they would not set
    the copied error code over loopback. This change also optimizes
    the path by removing copying and making tso_fragment cheaper.
4/4 follows-up to 3/4 by no longer allocated now unused memory.
    this was actually already in RFC patches, but dropped as I pared
    down the patch set during revisions.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 1f119f90 8ddab508

net/core/skbuff.c

+9 −5
Original line number Diff line number Diff line
@@ -3656,6 +3656,10 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, 
		skb_shinfo(nskb)->tx_flags |= skb_shinfo(head_skb)->tx_flags &

					      SKBTX_SHARED_FRAG;



		if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||

		    skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))

			goto err;



		while (pos < offset + len) {

			if (i >= nfrags) {

				BUG_ON(skb_headlen(list_skb));
@@ -3667,6 +3671,11 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, 


				BUG_ON(!nfrags);



				if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||

				    skb_zerocopy_clone(nskb, frag_skb,

						       GFP_ATOMIC))

					goto err;



				list_skb = list_skb->next;

			}
@@ -3678,11 +3687,6 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, 
				goto err;

			}



			if (unlikely(skb_orphan_frags(frag_skb, GFP_ATOMIC)))

				goto err;

			if (skb_zerocopy_clone(nskb, frag_skb, GFP_ATOMIC))

				goto err;



			*nskb_frag = *frag;

			__skb_frag_ref(nskb_frag);

			size = skb_frag_size(nskb_frag);

net/ipv4/tcp.c

+15 −9
Original line number Diff line number Diff line
@@ -1104,12 +1104,15 @@ static int linear_payload_sz(bool first_skb) 
	return 0;

}



static int select_size(const struct sock *sk, bool sg, bool first_skb)

static int select_size(const struct sock *sk, bool sg, bool first_skb, bool zc)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	int tmp = tp->mss_cache;



	if (sg) {

		if (zc)

			return 0;



		if (sk_can_gso(sk)) {

			tmp = linear_payload_sz(first_skb);

		} else {
@@ -1186,7 +1189,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
	int flags, err, copied = 0;

	int mss_now = 0, size_goal, copied_syn = 0;

	bool process_backlog = false;

	bool sg;

	bool sg, zc = false;

	long timeo;



	flags = msg->msg_flags;
@@ -1204,7 +1207,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
			goto out_err;

		}



		if (!(sk_check_csum_caps(sk) && sk->sk_route_caps & NETIF_F_SG))

		zc = sk_check_csum_caps(sk) && sk->sk_route_caps & NETIF_F_SG;

		if (!zc)

			uarg->zerocopy = 0;

	}
@@ -1281,6 +1285,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 


		if (copy <= 0 || !tcp_skb_can_collapse_to(skb)) {

			bool first_skb;

			int linear;



new_segment:

			/* Allocate new segment. If the interface is SG,
@@ -1294,9 +1299,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
				goto restart;

			}

			first_skb = tcp_rtx_and_write_queues_empty(sk);

			skb = sk_stream_alloc_skb(sk,

						  select_size(sk, sg, first_skb),

						  sk->sk_allocation,

			linear = select_size(sk, sg, first_skb, zc);

			skb = sk_stream_alloc_skb(sk, linear, sk->sk_allocation,

						  first_skb);

			if (!skb)

				goto wait_for_memory;
@@ -1325,13 +1329,13 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
			copy = msg_data_left(msg);



		/* Where to copy to? */

		if (skb_availroom(skb) > 0) {

		if (skb_availroom(skb) > 0 && !zc) {

			/* We have some space in skb head. Superb! */

			copy = min_t(int, copy, skb_availroom(skb));

			err = skb_add_data_nocache(sk, skb, &msg->msg_iter, copy);

			if (err)

				goto do_fault;

		} else if (!uarg || !uarg->zerocopy) {

		} else if (!zc) {

			bool merge = true;

			int i = skb_shinfo(skb)->nr_frags;

			struct page_frag *pfrag = sk_page_frag(sk);
@@ -1371,8 +1375,10 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
			pfrag->offset += copy;

		} else {

			err = skb_zerocopy_iter_stream(sk, skb, msg, copy, uarg);

			if (err == -EMSGSIZE || err == -EEXIST)

			if (err == -EMSGSIZE || err == -EEXIST) {

				tcp_mark_push(tp, skb);

				goto new_segment;

			}

			if (err < 0)

				goto do_error;

			copy = err;