linux-kernel - Re: [PATCH v2] io_uring: Fix reversed nonblock flag

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Date:   Fri, 4 Oct 2019 16:58:49 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH v2] io_uring: Fix reversed nonblock flag

On 04/10/2019 16:05, Jens Axboe wrote:
> On 10/4/19 4:07 AM, Pavel Begunkov (Silence) wrote:
>> From: Pavel Begunkov <asml.silence@...il.com>
>>
>> io_queue_link_head() accepts @force_nonblock flag, but io_ring_submit()
>> passes something opposite.
>>
>> v2: fix build error by test robot: Rebase from custom tree
>> Reported-by: kbuild test robot <lkp@...el.com>
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
>> ---
>>   fs/io_uring.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index c934f91c51e9..c909ea2b84e9 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -2703,6 +2703,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
>>   	struct io_kiocb *shadow_req = NULL;
>>   	bool prev_was_link = false;
>>   	int i, submit = 0;
>> +	bool force_nonblock = true;
>>   
>>   	if (to_submit > IO_PLUG_THRESHOLD) {
>>   		io_submit_state_start(&state, ctx, to_submit);
>> @@ -2710,9 +2711,9 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
>>   	}
>>   
>>   	for (i = 0; i < to_submit; i++) {
>> -		bool force_nonblock = true;
>>   		struct sqe_submit s;
>>   
>> +		force_nonblock = true;
>>   		if (!io_get_sqring(ctx, &s))
>>   			break;
>>   
>> @@ -2761,7 +2762,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
>>   
>>   	if (link)
>>   		io_queue_link_head(ctx, link, &link->submit, shadow_req,
>> -					block_for_last);
>> +					force_nonblock);
>>   	if (statep)
>>   		io_submit_state_end(statep);
> 
> Shouldn't this just be:
> 
>    		io_queue_link_head(ctx, link, &link->submit, shadow_req,
>  					!block_for_last);
> 
> We're outside the loop, so by definition at the end of what we need to
> do. We don't need to factor in the fiddling of force_nonblock here,
> it'll be false at this point anyway. Only exception is error handling,
> if the caller asked for more than what was in the ring. Not a big
> deal...

Thanks for explaining this, I'll resend.
Played safe because of breaks in the loop.

-- 
Yours sincerely,
Pavel Begunkov



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