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Tue, 17 Dec 2019 09:37:52 -0800 (PST) Subject: Re: [PATCH 3/3] io_uring: move *queue_link_head() from common path From: Jens Axboe To: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <17f7900c-385f-0dfa-11bf-af99d080f894@gmail.com> <76917820-052d-9597-133d-424fee3edade@kernel.dk> Message-ID: <5d4af2f6-26a2-b241-5131-3a0155cbbf22@kernel.dk> Date: Tue, 17 Dec 2019 10:37:52 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <76917820-052d-9597-133d-424fee3edade@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 12/17/19 9:45 AM, Jens Axboe wrote: > On 12/16/19 4:38 PM, Pavel Begunkov wrote: >> On 17/12/2019 02:22, Pavel Begunkov wrote: >>> Move io_queue_link_head() to links handling code in io_submit_sqe(), >>> so it wouldn't need extra checks and would have better data locality. >>> >>> Signed-off-by: Pavel Begunkov >>> --- >>> fs/io_uring.c | 32 ++++++++++++++------------------ >>> 1 file changed, 14 insertions(+), 18 deletions(-) >>> >>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>> index bac9e711e38d..a880ed1409cb 100644 >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -3373,13 +3373,15 @@ static bool io_submit_sqe(struct io_kiocb *req, struct io_submit_state *state, >>> struct io_kiocb **link) >>> { >>> struct io_ring_ctx *ctx = req->ctx; >>> + unsigned int sqe_flags; >>> int ret; >>> >>> + sqe_flags = READ_ONCE(req->sqe->flags); >>> req->user_data = READ_ONCE(req->sqe->user_data); >>> trace_io_uring_submit_sqe(ctx, req->user_data, true, req->in_async); >>> >>> /* enforce forwards compatibility on users */ >>> - if (unlikely(req->sqe->flags & ~SQE_VALID_FLAGS)) { >>> + if (unlikely(sqe_flags & ~SQE_VALID_FLAGS)) { >>> ret = -EINVAL; >>> goto err_req; >>> } >>> @@ -3402,10 +3404,10 @@ static bool io_submit_sqe(struct io_kiocb *req, struct io_submit_state *state, >>> if (*link) { >>> struct io_kiocb *head = *link; >>> >>> - if (req->sqe->flags & IOSQE_IO_DRAIN) >>> + if (sqe_flags & IOSQE_IO_DRAIN) >>> head->flags |= REQ_F_DRAIN_LINK | REQ_F_IO_DRAIN; >>> >>> - if (req->sqe->flags & IOSQE_IO_HARDLINK) >>> + if (sqe_flags & IOSQE_IO_HARDLINK) >>> req->flags |= REQ_F_HARDLINK; >>> >>> if (io_alloc_async_ctx(req)) { >>> @@ -3421,9 +3423,15 @@ static bool io_submit_sqe(struct io_kiocb *req, struct io_submit_state *state, >>> } >>> trace_io_uring_link(ctx, req, head); >>> list_add_tail(&req->link_list, &head->link_list); >>> - } else if (req->sqe->flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) { >>> + >>> + /* last request of a link, enqueue the link */ >>> + if (!(sqe_flags & IOSQE_IO_LINK)) { >> >> This looks suspicious (as well as in the current revision). Returning back >> to my questions a few days ago can sqe->flags have IOSQE_IO_HARDLINK, but not >> IOSQE_IO_LINK? I don't find any check. >> >> In other words, should it be as follows? >> !(sqe_flags & (IOSQE_IO_LINK|IOSQE_IO_HARDLINK)) > > Yeah, I think that should check for both. I'm fine with either approach > in general: > > - IOSQE_IO_HARDLINK must have IOSQE_IO_LINK set > > or > > - IOSQE_IO_HARDLINK implies IOSQE_IO_LINK > > Seems like the former is easier to verify in terms of functionality, > since we can rest easy if we check this early and -EINVAL if that isn't > the case. > > What do you think? If you agree, want to send in a patch for that for 5.5? Then I can respin for-5.6/io_uring on top of that, and we can apply your cleanups there. -- Jens Axboe