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Merge branch 'net-zerocopy-refine'

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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: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2017-12-27 16:44:14 -05:00
commit 55b07a65e1
2 changed files with 24 additions and 14 deletions
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14
net/core/skbuff.c
View File

@ -3656,6 +3656,10 @@ normal:
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 @@ normal:
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 @@ normal:
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);

24
net/ipv4/tcp.c
View File

@ -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 @@ restart:
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 @@ new_segment:
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 @@ new_segment:
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 @@ new_segment:
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;