linux-kernel - Re: [PATCH v3 0/4] forbid fix {SQ,IO}POLL

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Message-ID: <d1d92d99-c6b1-fc6e-ea1d-6c2e5097d83f@gmail.com>
Date:   Thu, 4 Jun 2020 22:22:47 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/4] forbid fix {SQ,IO}POLL

On 04/06/2020 20:06, Jens Axboe wrote:
> On 6/3/20 12:51 PM, Jens Axboe wrote:
>> On 6/3/20 9:03 AM, Pavel Begunkov wrote:
>>> The first one adds checks {SQPOLL,IOPOLL}. IOPOLL check can be
>>> moved in the common path later, or rethinked entirely, e.g.
>>> not io_iopoll_req_issued()'ed for unsupported opcodes.
>>>
>>> 3 others are just cleanups on top.
>>>
>>>
>>> v2: add IOPOLL to the whole bunch of opcodes in [1/4].
>>>     dirty and effective.
>>> v3: sent wrong set in v2, re-sending right one 
>>>
>>> Pavel Begunkov (4):
>>>   io_uring: fix {SQ,IO}POLL with unsupported opcodes
>>>   io_uring: do build_open_how() only once
>>>   io_uring: deduplicate io_openat{,2}_prep()
>>>   io_uring: move send/recv IOPOLL check into prep
>>>
>>>  fs/io_uring.c | 94 ++++++++++++++++++++++++++-------------------------
>>>  1 file changed, 48 insertions(+), 46 deletions(-)
>>
>> Thanks, applied.
> 
> #1 goes too far, provide/remove buffers is fine with iopoll. I'll
> going to edit the patch.

Conceptually it should work, but from a quick look:

- io_provide_buffers() drops a ref from req->refs, which should've
been used by iopoll*. E.g. io_complete_rw_iopoll() doesn't do that.

- it doesn't set REQ_F_IOPOLL_COMPLETED, thus iopoll* side will
call req->file->iopoll().

-- 
Pavel Begunkov