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net-zerocopy: Set zerocopy hint when data is copied 

Set zerocopy hint, event when falling back to copy, so that the
pending data can be efficiently received using zerocopy when
possible.

Signed-off-by: Arjun Roy <arjunroy@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Arjun Roy 2020-12-02 14:53:48 -08:00 committed by Jakub Kicinski
parent f21a3c4803
commit 0c3936d32f
1 changed files with 45 additions and 0 deletions
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45
net/ipv4/tcp.c
View File

@ -1800,6 +1800,43 @@ static int find_next_mappable_frag(const skb_frag_t *frag,
return offset;
}
static void tcp_zerocopy_set_hint_for_skb(struct sock *sk,
struct tcp_zerocopy_receive *zc,
struct sk_buff *skb, u32 offset)
{
u32 frag_offset, partial_frag_remainder = 0;
int mappable_offset;
skb_frag_t *frag;
/* worst case: skip to next skb. try to improve on this case below */
zc->recv_skip_hint = skb->len - offset;
/* Find the frag containing this offset (and how far into that frag) */
frag = skb_advance_to_frag(skb, offset, &frag_offset);
if (!frag)
return;
if (frag_offset) {
struct skb_shared_info *info = skb_shinfo(skb);
/* We read part of the last frag, must recvmsg() rest of skb. */
if (frag == &info->frags[info->nr_frags - 1])
return;
/* Else, we must at least read the remainder in this frag. */
partial_frag_remainder = skb_frag_size(frag) - frag_offset;
zc->recv_skip_hint -= partial_frag_remainder;
++frag;
}
/* partial_frag_remainder: If part way through a frag, must read rest.
* mappable_offset: Bytes till next mappable frag, *not* counting bytes
* in partial_frag_remainder.
*/
mappable_offset = find_next_mappable_frag(frag, zc->recv_skip_hint);
zc->recv_skip_hint = mappable_offset + partial_frag_remainder;
}
static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int nonblock, int flags,
struct scm_timestamping_internal *tss,
@ -1830,6 +1867,14 @@ static int receive_fallback_to_copy(struct sock *sk,
return err;
zc->copybuf_len = err;
if (likely(zc->copybuf_len)) {
struct sk_buff *skb;
u32 offset;
skb = tcp_recv_skb(sk, tcp_sk(sk)->copied_seq, &offset);
if (skb)
tcp_zerocopy_set_hint_for_skb(sk, zc, skb, offset);
}
return 0;
}