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Date:   Mon, 12 Jul 2021 12:34:23 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc:     Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-aio@kvack.org
Subject: Re: [PATCH 1/2] mm/readahead: Add gfp_flags to ractl
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On Sun, Jul 11, 2021 at 04:09:26PM +0100, Matthew Wilcox (Oracle) wrote:
> It is currently possible for an I/O request that specifies IOCB_NOWAIT
> to sleep waiting for I/O to complete in order to allocate pages for
> readahead.  In order to fix that, we need the caller to be able to
> specify the GFP flags to use for memory allocation in the rest of the
> readahead path.

The file systems also need to respect it for their bio or private
data allocation.  And be able to cope with failure, which they currently
don't have to for sleeping bio allocations.