Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 24 Jun 2020 17:41:27 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Dave Chinner <david@fromorbit.com>, io-uring@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org,
        Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 05/15] mm: allow read-ahead with IOCB_NOWAIT set
Message-ID: <20200624164127.GP21350@casper.infradead.org>
References: <20200618144355.17324-1-axboe@kernel.dk>
 <20200618144355.17324-6-axboe@kernel.dk>
 <20200624010253.GB5369@dread.disaster.area>
 <20200624014645.GJ21350@casper.infradead.org>
 <bad52be9-ae44-171b-8dbf-0d98eedcadc0@kernel.dk>
 <70b0427c-7303-8f45-48bd-caa0562a2951@kernel.dk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <70b0427c-7303-8f45-48bd-caa0562a2951@kernel.dk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jun 24, 2020 at 09:35:19AM -0600, Jens Axboe wrote:
> On 6/24/20 9:00 AM, Jens Axboe wrote:
> > On 6/23/20 7:46 PM, Matthew Wilcox wrote:
> >> I'd be quite happy to add a gfp_t to struct readahead_control.
> >> The other thing I've been looking into for other reasons is adding
> >> a memalloc_nowait_{save,restore}, which would avoid passing down
> >> the gfp_t.
> > 
> > That was my first thought, having the memalloc_foo_save/restore for
> > this. I don't think adding a gfp_t to readahead_control is going
> > to be super useful, seems like the kind of thing that should be
> > non-blocking by default.
> 
> We're already doing memalloc_nofs_save/restore in
> page_cache_readahead_unbounded(), so I think all we need is to just do a
> noio dance in generic_file_buffered_read() and that should be enough.

I think we can still sleep though, right?  I was thinking more
like this:

http://git.infradead.org/users/willy/linux.git/shortlog/refs/heads/memalloc