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Sat, 24 Jan 2026 07:12:39 -0800 (PST) Message-ID: <30ee2371-f82f-4b29-9276-71b8cc12b87d@kernel.dk> Date: Sat, 24 Jan 2026 08:12:38 -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 liburing 0/2] Add support for IORING_SETUP_SQ_REWIND To: Pavel Begunkov , io-uring@vger.kernel.org References: <176912275112.522897.5400530813917730862.b4-ty@kernel.dk> <517fc5f0-5e6d-46ef-800d-9ef4428278a1@kernel.dk> <2d2da3b2-74c6-4605-8d13-3f0cdc67191e@kernel.dk> <9c10b8e7-d64c-491a-96b3-fc26863e0dbf@gmail.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <9c10b8e7-d64c-491a-96b3-fc26863e0dbf@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/24/26 3:44 AM, Pavel Begunkov wrote: > On 1/23/26 19:04, Jens Axboe wrote: >> On 1/23/26 7:14 AM, Pavel Begunkov wrote: >>> On 1/22/26 23:05, Jens Axboe wrote: >>>> On 1/22/26 3:59 PM, Jens Axboe wrote: >>>>> >>>>> On Wed, 21 Jan 2026 22:23:20 +0000, Pavel Begunkov wrote: >>>>>> Add liburing support and tests for IORING_SETUP_SQ_REWIND. >>>>>> >>>>>> Pavel Begunkov (2): >>>>>> src/queue: Add support for non circular SQ >>>>>> tests: add SETUP_SQ_REWIND tests >>>>>> >>>>>> src/include/liburing.h | 5 ++++- >>>>>> src/include/liburing/io_uring.h | 12 ++++++++++++ >>>>>> src/queue.c | 5 +++++ >>>>>> test/test.h | 2 ++ >>>>>> 4 files changed, 23 insertions(+), 1 deletion(-) >>>>>> >>>>>> [...] >>>>> >>>>> Applied, thanks! >>>>> >>>>> [1/2] src/queue: Add support for non circular SQ >>>>> commit: c22129cf0b8c936eb478d920ef84e53d89c6a5cc >>>>> [2/2] tests: add SETUP_SQ_REWIND tests >>>>> commit: 346c063d16bda52f02d00feb744aafe35b4002a9 >>>> >>>> Hmm I do think you're missing some spots though, no? >>>> >>>> diff --git a/src/include/liburing.h b/src/include/liburing.h >>>> index 987b28aaf99e..016be1e80ef2 100644 >>>> --- a/src/include/liburing.h >>>> +++ b/src/include/liburing.h >>>> @@ -1702,8 +1702,13 @@ IOURINGINLINE unsigned io_uring_load_sq_head(const struct io_uring *ring) >>>> IOURINGINLINE unsigned io_uring_sq_ready(const struct io_uring *ring) >>>> LIBURING_NOEXCEPT >>>> { >>>> + unsigned head = 0; >>>> + >>>> + if (!(ring->flags & IORING_SETUP_SQ_REWIND)) >>>> + head = io_uring_load_sq_head(ring); >>> >>> The head should already be zero. Actually, sounds like the get_sqe >>> hunk from the patch is not needed either. >> >> Yeah agree, I think they are both false alarms. Might warrant a comment >> though. Or maybe we just fold it into io_uring_load_sq_head()? > > What I'm implying is that the > > + if (!(ring->flags & IORING_SETUP_SQ_REWIND)) > + head = io_uring_load_sq_head(ring); > + > > change from the original patch for normal 64B _io_uring_get_sqe() > doesn't seem to be necessary. I need to take a look, but that's > a good thing since the function is somewhat frequently called and > inlined. > > That would leave __io_uring_flush_sq() to be the only place > checking the flag, so maybe comments would better to be put > there. If you have time, would you mind checking the current repo and sending a patch? Looks like I messed up a bit and committed some of these bits with: commit 5d1c94f754f3bca156d84b4ebcaf2f211dcd09f2 Author: Jens Axboe Date: Thu Jan 22 17:11:53 2026 -0700 test/sqe-mixed-noop: add SQ_REWIND testing inadvertently as I was doing some testing. -- Jens Axboe