Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 0/2][for-next] cleanup submission path
From:   Jens Axboe <axboe@kernel.dk>
To:     Pavel Begunkov <asml.silence@gmail.com>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1572189860.git.asml.silence@gmail.com>
 <666ed447-ba8f-29e7-237f-de8044aa63ea@kernel.dk>
 <5ec9bd14-d8f2-32e6-7f25-0ca7256c408a@gmail.com>
 <aac65fe2-6c51-3baf-eee7-af5a8f633bf2@kernel.dk>
Message-ID: <d39a878f-9dac-1457-6bba-01afc6268a84@kernel.dk>
Date:   Sun, 27 Oct 2019 10:56:46 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <aac65fe2-6c51-3baf-eee7-af5a8f633bf2@kernel.dk>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/27/19 10:49 AM, Jens Axboe wrote:
> On 10/27/19 10:44 AM, Pavel Begunkov wrote:
>> On 27/10/2019 19:32, Jens Axboe wrote:
>>> On 10/27/19 9:35 AM, Pavel Begunkov wrote:
>>>> A small cleanup of very similar but diverged io_submit_sqes() and
>>>> io_ring_submit()
>>>>
>>>> Pavel Begunkov (2):
>>>>      io_uring: handle mm_fault outside of submission
>>>>      io_uring: merge io_submit_sqes and io_ring_submit
>>>>
>>>>     fs/io_uring.c | 116 ++++++++++++++------------------------------------
>>>>     1 file changed, 33 insertions(+), 83 deletions(-)
>>>
>>> I like the cleanups here, but one thing that seems off is the
>>> assumption that io_sq_thread() always needs to grab the mm. If
>>> the sqes processed are just READ/WRITE_FIXED, then it never needs
>>> to grab the mm.
>>> Yeah, we removed it to fix bugs. Personally, I think it would be
>> clearer to do lazy grabbing conditionally, rather than have two
>> functions. And in this case it's easier to do after merging.
>>
>> Do you prefer to return it back first?
> 
> Ah I see, no I don't care about that.

OK, looked at the post-patches state. It's still not correct. You are
grabbing the mm from io_sq_thread() unconditionally. We should not do
that, only if the sqes we need to submit need mm context.

-- 
Jens Axboe