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tcp: fix mem under-charging with zerocopy sendmsg()

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We got reports of following warning in inet_sock_destruct()

	WARN_ON(sk_forward_alloc_get(sk));

Whenever we add a non zero-copy fragment to a pure zerocopy skb,
we have to anticipate that whole skb->truesize will be uncharged
when skb is finally freed.

skb->data_len is the payload length. But the memory truesize
estimated by __zerocopy_sg_from_iter() is page aligned.

Fixes: 9b65b17db7 ("net: avoid double accounting for pure zerocopy skbs")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Talal Ahmad <talalahmad@google.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Link: https://lore.kernel.org/r/20220201065254.680532-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2022-01-31 22:52:54 -08:00 committed by Jakub Kicinski
parent e42e70ad6a
commit 479f554723
1 changed files with 5 additions and 2 deletions
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7
net/ipv4/tcp.c
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@ -1322,10 +1322,13 @@ new_segment:
/* skb changing from pure zc to mixed, must charge zc */
if (unlikely(skb_zcopy_pure(skb))) {
if (!sk_wmem_schedule(sk, skb->data_len))
u32 extra = skb->truesize -
SKB_TRUESIZE(skb_end_offset(skb));
if (!sk_wmem_schedule(sk, extra))
goto wait_for_space;
sk_mem_charge(sk, skb->data_len);
sk_mem_charge(sk, extra);
skb_shinfo(skb)->flags &= ~SKBFL_PURE_ZEROCOPY;
}