linux-kernel - Re: [PATCH 1/3] io_uring/net: only import send

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Message-ID: <ee6c175c-d5b7-4a1f-97b3-4ff6166c5c73@gmail.com>
Date: Fri, 21 Mar 2025 20:38:32 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Caleb Sander Mateos <csander@...estorage.com>,
 Jens Axboe <axboe@...nel.dk>, Ming Lei <ming.lei@...hat.com>,
 Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>
Cc: Xinyu Zhang <xizhang@...estorage.com>, io-uring@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Subject: Re: [PATCH 1/3] io_uring/net: only import send_zc buffer once

On 3/21/25 18:48, Caleb Sander Mateos wrote:
> io_send_zc() guards its call to io_send_zc_import() with if (!done_io)
> in an attempt to avoid calling it redundantly on the same req. However,
> if the initial non-blocking issue returns -EAGAIN, done_io will stay 0.
> This causes the subsequent issue to unnecessarily re-import the buffer.
> 
> Add an explicit flag "imported" to io_sr_msg to track if its buffer has
> already been imported. Clear the flag in io_send_zc_prep(). Call
> io_send_zc_import() and set the flag in io_send_zc() if it is unset.

lgtm. Maybe there is a way to put it into req->flags and combine
with REQ_F_IMPORT_BUFFER, but likely just an idea for the future.

-- 
Pavel Begunkov