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Date:   Wed, 15 Feb 2023 22:08:17 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH] brd: mark as nowait compatible
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On Wed, Feb 15, 2023 at 04:43:47PM -0700, Jens Axboe wrote:
> By default, non-mq drivers do not support nowait. This causes io_uring
> to use a slower path as the driver cannot be trust not to block. brd
> can safely set the nowait flag, as worst case all it does is a NOIO
> allocation.

But a NOIO allocation can block.  I think we need to do a
GFP_NOWAIT allocation in brd_insert_page if the NOWAIT flag is set.