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Subject: Re: [PATCH] io_uring: fix deferred req iovec leak
To:     Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <e143e45a34dce9d271fc4a3b32f7620c5a7377c1.1581007844.git.asml.silence@gmail.com>
 <d8486857-ccd3-41bd-2ef7-5ac4781dbd5f@gmail.com>
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 <6e7207b6-95c4-4287-5872-fb05abf60e88@kernel.dk>
From:   Pavel Begunkov <asml.silence@gmail.com>
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Message-ID: <4f7f61d3-b3f9-43db-ad32-ee502dc06c8b@gmail.com>
Date:   Thu, 6 Feb 2020 23:00:41 +0300
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
 linux-kernel@vger.kernel.org
Message-ID: <4f7f61d3-b3f9-43db-ad32-ee502dc06c8b@gmail.com>
Subject: Re: [PATCH] io_uring: fix deferred req iovec leak
References: <e143e45a34dce9d271fc4a3b32f7620c5a7377c1.1581007844.git.asml.silence@gmail.com>
 <d8486857-ccd3-41bd-2ef7-5ac4781dbd5f@gmail.com>
 <f6a1d5aa-f84d-168e-4fdf-6fb895fc09df@gmail.com>
 <6e7207b6-95c4-4287-5872-fb05abf60e88@kernel.dk>
In-Reply-To: <6e7207b6-95c4-4287-5872-fb05abf60e88@kernel.dk>

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On 06/02/2020 22:56, Jens Axboe wrote:
> On 2/6/20 10:16 AM, Pavel Begunkov wrote:
>> On 06/02/2020 20:04, Pavel Begunkov wrote:
>>> On 06/02/2020 19:51, Pavel Begunkov wrote:
>>>> After defer, a request will be prepared, that includes allocating io=
vec
>>>> if needed, and then submitted through io_wq_submit_work() but not cu=
stom
>>>> handler (e.g. io_rw_async()/io_sendrecv_async()). However, it'll lea=
k
>>>> iovec, as it's in io-wq and the code goes as follows:
>>>>
>>>> io_read() {
>>>> 	if (!io_wq_current_is_worker())
>>>> 		kfree(iovec);
>>>> }
>>>>
>>>> Put all deallocation logic in io_{read,write,send,recv}(), which wil=
l
>>>> leave the memory, if going async with -EAGAIN.
>>>>
>>> Interestingly, this will fail badly if it returns -EAGAIN from io-wq =
context.
>>> Apparently, I need to do v2.
>>>
>> Or not...
>> Jens, can you please explain what's with the -EAGAIN handling in
>> io_wq_submit_work()? Checking the code, it seems neither of
>> read/write/recv/send can return -EAGAIN from async context (i.e.
>> force_nonblock=3Dfalse). Are there other ops that can do it?
>=20
> Nobody should return -EAGAIN with force_nonblock=3Dfalse, they should
> end the io_kiocb inline for that.
>=20

If so for those 4, then the patch should work well.

--=20
Pavel Begunkov


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