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Mon, 17 Feb 2025 07:06:51 -0800 (PST) Message-ID: Date: Mon, 17 Feb 2025 08:06:50 -0700 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] io_uring/rw: forbid multishot async reads To: Pavel Begunkov , io-uring@vger.kernel.org References: <49f065f7b88b7a67190ce65919e7c93c04b3a74b.1739799395.git.asml.silence@gmail.com> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 2/17/25 7:12 AM, Pavel Begunkov wrote: > On 2/17/25 13:58, Jens Axboe wrote: >> On 2/17/25 6:37 AM, Pavel Begunkov wrote: >>> At the moment we can't sanely handle queuing an async request from a >>> multishot context, so disable them. It shouldn't matter as pollable >>> files / socekts don't normally do async. >> >> Having something pollable that can return -EIOCBQUEUED is odd, but >> that's just a side comment. >> >> >>> diff --git a/io_uring/rw.c b/io_uring/rw.c >>> index 96b42c331267..4bda46c5eb20 100644 >>> --- a/io_uring/rw.c >>> +++ b/io_uring/rw.c >>> @@ -878,7 +878,15 @@ static int __io_read(struct io_kiocb *req, unsigned int issue_flags) >>>       if (unlikely(ret)) >>>           return ret; >>>   -    ret = io_iter_do_read(rw, &io->iter); >>> +    if (unlikely(req->opcode == IORING_OP_READ_MULTISHOT)) { >>> +        void *cb_copy = rw->kiocb.ki_complete; >>> + >>> +        rw->kiocb.ki_complete = NULL; >>> +        ret = io_iter_do_read(rw, &io->iter); >>> +        rw->kiocb.ki_complete = cb_copy; >>> +    } else { >>> +        ret = io_iter_do_read(rw, &io->iter); >>> +    } >> >> This looks a bit odd. Why can't io_read_mshot() just clear >> ->ki_complete? > > Forgot about that one, as for restoring it back, io_uring compares > or calls ->ki_complete in a couple of places, this way the patch > is more contained. It can definitely be refactored on top. I'd be tempted to do that for the fix too, the patch as-is is a bit of an eye sore... Hmm. -- Jens Axboe