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From: Pavel Begunkov <asml.silence@gmail.com>
To: David Ahern <dsahern@kernel.org>,
	io-uring@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: "David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Jonathan Lemon <jonathan.lemon@gmail.com>,
	Willem de Bruijn <willemb@google.com>,
	Jens Axboe <axboe@kernel.dk>,
	kernel-team@fb.com
Subject: Re: [PATCH net-next v4 11/27] tcp: support externally provided ubufs
Date: Fri, 8 Jul 2022 15:03:46 +0100	[thread overview]
Message-ID: <45cd36ee-ef99-fb67-df8d-218603facfd7@gmail.com> (raw)
In-Reply-To: <62e1daba-fb20-bf20-5c4d-c31770e5420e@kernel.org>

On 7/8/22 05:06, David Ahern wrote:
> On 7/7/22 5:49 AM, Pavel Begunkov wrote:
>> Teach ipv4/udp how to use external ubuf_info provided in msghdr and
> 
> ipv4/tcp?

Ehh, just tcp. Thanks, I updated the branches


>> also prepare it for managed frags by sprinkling
>> skb_zcopy_downgrade_managed() when it could mix managed and not managed
>> frags.
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
>> ---
>>   net/ipv4/tcp.c | 32 ++++++++++++++++++++------------
>>   1 file changed, 20 insertions(+), 12 deletions(-)
>>
>> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
>> index 390eb3dc53bd..a81f694af5e9 100644
>> --- a/net/ipv4/tcp.c
>> +++ b/net/ipv4/tcp.c
>> @@ -1223,17 +1223,23 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
>>   
>>   	flags = msg->msg_flags;
>>   
>> -	if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) {
>> +	if ((flags & MSG_ZEROCOPY) && size) {
>>   		skb = tcp_write_queue_tail(sk);
>> -		uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
>> -		if (!uarg) {
>> -			err = -ENOBUFS;
>> -			goto out_err;
>> -		}
>>   
>> -		zc = sk->sk_route_caps & NETIF_F_SG;
>> -		if (!zc)
>> -			uarg->zerocopy = 0;
>> +		if (msg->msg_ubuf) {
>> +			uarg = msg->msg_ubuf;
>> +			net_zcopy_get(uarg);
>> +			zc = sk->sk_route_caps & NETIF_F_SG;
>> +		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
>> +			uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
>> +			if (!uarg) {
>> +				err = -ENOBUFS;
>> +				goto out_err;
>> +			}
>> +			zc = sk->sk_route_caps & NETIF_F_SG;
>> +			if (!zc)
>> +				uarg->zerocopy = 0;
>> +		}
>>   	}
>>   
>>   	if (unlikely(flags & MSG_FASTOPEN || inet_sk(sk)->defer_connect) &&
>> @@ -1356,9 +1362,11 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
>>   
>>   			copy = min_t(int, copy, pfrag->size - pfrag->offset);
>>   
>> -			if (tcp_downgrade_zcopy_pure(sk, skb))
>> -				goto wait_for_space;
>> -
>> +			if (unlikely(skb_zcopy_pure(skb) || skb_zcopy_managed(skb))) {
>> +				if (tcp_downgrade_zcopy_pure(sk, skb))
>> +					goto wait_for_space;
>> +				skb_zcopy_downgrade_managed(skb);
>> +			}
>>   			copy = tcp_wmem_schedule(sk, copy);
>>   			if (!copy)
>>   				goto wait_for_space;
> 
> You dropped the msg->msg_ubuf checks on jump labels. Removing the one
> you had at 'out_nopush' I agree with based on my tests (i.e, it is not
> needed).

It was an optimisation, which I dropped for simplicity. Will be sending it
and couple more afterwards.


> The one at 'out_err' seems like it is needed - but it has been a few
> weeks since I debugged that case. I believe the error path I was hitting
> was sk_stream_wait_memory with MSG_DONTWAIT flag set meaning timeout is
> 0 and it jumps there with EPIPE.

Currently, it's consistent with MSG_ZEROCOPY ubuf_info, we grab a ubuf_info
reference at the beginning (msg_zerocopy_realloc() for MSG_ZEROCOPY and
net_zcopy_get() for msg_ubuf), and then release it at the end
with net_zcopy_put() or net_zcopy_put_abort().

All users, e.g. skb_zerocopy_iter_stream(), have to grab a new reference,
skb_zcopy_set() -> net_zcopy_get().

Not sure I see any issue, and if there is it sounds that it should also
be affecting MSG_ZEROCOPY.


-- 
Pavel Begunkov

  reply	other threads:[~2022-07-08 14:05 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-07 11:49 [PATCH net-next v4 00/27] io_uring zerocopy send Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 01/27] ipv4: avoid partial copy for zc Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 02/27] ipv6: " Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 03/27] skbuff: don't mix ubuf_info from different sources Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 04/27] skbuff: add SKBFL_DONT_ORPHAN flag Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 05/27] skbuff: carry external ubuf_info in msghdr Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 06/27] net: Allow custom iter handler " Pavel Begunkov
2022-07-11 12:20   ` Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 07/27] net: introduce managed frags infrastructure Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 08/27] net: introduce __skb_fill_page_desc_noacc Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 09/27] ipv4/udp: support externally provided ubufs Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 10/27] ipv6/udp: " Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 11/27] tcp: " Pavel Begunkov
2022-07-08  4:06   ` David Ahern
2022-07-08 14:03     ` Pavel Begunkov [this message]
2022-07-13 23:38       ` David Ahern
2022-07-07 11:49 ` [PATCH net-next v4 12/27] io_uring: initialise msghdr::msg_ubuf Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 13/27] io_uring: export io_put_task() Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 14/27] io_uring: add zc notification infrastructure Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 15/27] io_uring: cache struct io_notif Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 16/27] io_uring: complete notifiers in tw Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 17/27] io_uring: add rsrc referencing for notifiers Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 18/27] io_uring: add notification slot registration Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 19/27] io_uring: wire send zc request type Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 20/27] io_uring: account locked pages for non-fixed zc Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 21/27] io_uring: allow to pass addr into sendzc Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 22/27] io_uring: sendzc with fixed buffers Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 23/27] io_uring: flush notifiers after sendzc Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 24/27] io_uring: rename IORING_OP_FILES_UPDATE Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 25/27] io_uring: add zc notification flush requests Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 26/27] io_uring: enable managed frags with register buffers Pavel Begunkov
2022-07-07 11:49 ` [PATCH net-next v4 27/27] selftests/io_uring: test zerocopy send Pavel Begunkov
2022-07-08  4:10 ` [PATCH net-next v4 00/27] io_uring " David Ahern
2022-07-08 14:26   ` Pavel Begunkov
2022-07-11 12:56     ` Pavel Begunkov
2022-07-13 23:45       ` David Ahern
2022-07-14 18:55         ` Pavel Begunkov
2022-07-18  2:19           ` David Ahern
2022-07-20 13:32             ` Pavel Begunkov
2022-07-24 18:28             ` David Ahern
2022-07-27 10:51               ` Pavel Begunkov
2022-07-29 22:30                 ` David Ahern
2022-09-26 20:08               ` Pavel Begunkov
2022-09-28 19:31                 ` David Ahern
2022-09-28 20:11                   ` Pavel Begunkov

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