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Mon, 17 Feb 2025 07:37:54 -0800 (PST) Message-ID: <205ed24e-238f-497e-9990-6bcb08acaf61@kernel.dk> Date: Mon, 17 Feb 2025 08:37:53 -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: 7bit On 2/17/25 7:08 AM, Pavel Begunkov wrote: > On 2/17/25 13:58, Jens Axboe wrote: >> On 2/17/25 6:37 AM, Pavel Begunkov wrote: >> >> The kiocb semantics of ki_complete == NULL -> sync kiocb is also odd, > > That's what is_sync_kiocb() does. Would be cleaner to use > init_sync_kiocb(), but there is a larger chance to do sth > wrong as it's reinitialises it entirely. Sorry if that wasn't clear, yeah I do realize this is what is_sync_kiocb() checks. I do agree that manually clearing is saner. >> but probably fine for this case as read mshot strictly deals with >> pollable files. Otherwise you'd just be blocking off this issue, >> regardless of whether or not IOCB_NOWAIT is set. >> >> In any case, it'd be much nicer to container this in io_read_mshot() >> where it arguably belongs, rather than sprinkle it in __io_read(). >> Possible? > > That's what I tried first, but __io_read() -> io_rw_init_file() > reinitialises it, so I don't see any good way without some > broader refactoring. Would it be bad? The only reason the kiocb init part is in there is because of the ->iopoll() check, that could still be there with the rest of the init going into normal prep (as it arguably should). Something like the below, totally untested... diff --git a/io_uring/rw.c b/io_uring/rw.c index 16f12f94943f..f8dd9a9fe9ca 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -264,6 +264,9 @@ static int io_prep_rw_pi(struct io_kiocb *req, struct io_rw *rw, int ddir, return ret; } +static void io_complete_rw(struct kiocb *kiocb, long res); +static void io_complete_rw_iopoll(struct kiocb *kiocb, long res); + static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, int ddir, bool do_import) { @@ -288,6 +291,18 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, } rw->kiocb.dio_complete = NULL; rw->kiocb.ki_flags = 0; + if (req->ctx->flags & IORING_SETUP_IOPOLL) { + if (!(rw->kiocb.ki_flags & IOCB_DIRECT)) + return -EOPNOTSUPP; + + rw->kiocb.private = NULL; + rw->kiocb.ki_flags |= IOCB_HIPRI; + rw->kiocb.ki_complete = io_complete_rw_iopoll; + } else { + if (rw->kiocb.ki_flags & IOCB_HIPRI) + return -EINVAL; + rw->kiocb.ki_complete = io_complete_rw; + } rw->addr = READ_ONCE(sqe->addr); rw->len = READ_ONCE(sqe->len); @@ -810,23 +825,15 @@ static int io_rw_init_file(struct io_kiocb *req, fmode_t mode, int rw_type) ((file->f_flags & O_NONBLOCK && !(req->flags & REQ_F_SUPPORT_NOWAIT)))) req->flags |= REQ_F_NOWAIT; - if (ctx->flags & IORING_SETUP_IOPOLL) { - if (!(kiocb->ki_flags & IOCB_DIRECT) || !file->f_op->iopoll) + if (kiocb->ki_flags & IOCB_HIPRI) { + if (!file->f_op->iopoll) return -EOPNOTSUPP; - - kiocb->private = NULL; - kiocb->ki_flags |= IOCB_HIPRI; - kiocb->ki_complete = io_complete_rw_iopoll; req->iopoll_completed = 0; if (ctx->flags & IORING_SETUP_HYBRID_IOPOLL) { /* make sure every req only blocks once*/ req->flags &= ~REQ_F_IOPOLL_STATE; req->iopoll_start = ktime_get_ns(); } - } else { - if (kiocb->ki_flags & IOCB_HIPRI) - return -EINVAL; - kiocb->ki_complete = io_complete_rw; } if (req->flags & REQ_F_HAS_METADATA) { -- Jens Axboe