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Date: Tue, 1 Apr 2025 12:56:44 -0600
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Subject: Re: [PATCH] io_uring/zcrx: return early from io_zcrx_recv_skb if
readlen is 0
To: David Wei <dw@davidwei.uk>, io-uring@vger.kernel.org
Cc: Pavel Begunkov <asml.silence@gmail.com>
References: <20250401182813.1115909-1-dw@davidwei.uk>
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From: Jens Axboe <axboe@kernel.dk>
In-Reply-To: <20250401182813.1115909-1-dw@davidwei.uk>
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On 4/1/25 12:28 PM, David Wei wrote:
> When readlen is set for a recvzc request, tcp_read_sock() will call
> io_zcrx_recv_skb() one final time with len == desc->count == 0. This is
> caused by the !desc->count check happening too late. The offset + 1 !=
> skb->len happens earlier and causes the while loop to continue.
>
> Fix this in io_zcrx_recv_skb() instead of tcp_read_sock(). Return early
> if len is 0 i.e. the read is done.
Needs a Fixes tag, which looks like it should be:
Fixes: 6699ec9a23f8 ("io_uring/zcrx: add a read limit to recvzc requests")
?
> Signed-off-by: David Wei <dw@davidwei.uk>
> ---
> io_uring/zcrx.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
> index 9c95b5b6ec4e..d1dd25e7cf4a 100644
> --- a/io_uring/zcrx.c
> +++ b/io_uring/zcrx.c
> @@ -818,6 +818,8 @@ io_zcrx_recv_skb(read_descriptor_t *desc, struct sk_buff *skb,
> int ret = 0;
>
> len = min_t(size_t, len, desc->count);
> + if (!len)
> + goto out;
just return 0 here? Jumping to out would make more sense if there
are things to fixup/account at this point, but it's just going
to find offset == start_off and return 'ret', which is 0 anyway.
--
Jens Axboe