Re: [PATCH 05/27] block: ensure that async polled IO is marked REQ_NOWAIT

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On 12/4/18 7:48 AM, Christoph Hellwig wrote:
> On Fri, Nov 30, 2018 at 10:17:49AM -0700, Jens Axboe wrote:
>>> Setting REQ_NOWAIT from inside the block layer will make the code that
>>> submits requests harder to review. Have you considered to make this code
>>> fail I/O if REQ_NOWAIT has not been set and to require that the context
>>> that submits I/O sets REQ_NOWAIT?
>>
>> It's technically still feasible to do for sync polled IO, it's only
>> the async case that makes it a potential deadlock.
> 
> I wonder if we want a REQ_ASYNC_POLL compound flag #define that sets
> REQ_POLL and REQ_NOWAIT to make this blindly obvious.

Yeah that might make sense, all the async cases should certainly use it,
and sync can keep using REQ_POLL. I'll add that and fold where I can.

-- 
Jens Axboe




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