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Date: Tue, 4 Dec 2018 15:48:20 +0100
From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Bart Van Assche <bvanassche@acm.org>, linux-block@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, hch@lst.de
Subject: Re: [PATCH 05/27] block: ensure that async polled IO is marked
 REQ_NOWAIT
Message-ID: <20181204144820.GC3180@lst.de>
References: <20181130165646.27341-1-axboe@kernel.dk> <20181130165646.27341-6-axboe@kernel.dk> <1543597960.4347.3.camel@acm.org> <6044f9e1-0175-823b-b923-998094bdca72@kernel.dk>
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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.