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;
MIME-Version: 1.0
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>
 <20200624164127.GP21350@casper.infradead.org> <8835b6f2-b3c5-c9a0-2119-1fb161cf87dd@kernel.dk>
In-Reply-To: <8835b6f2-b3c5-c9a0-2119-1fb161cf87dd@kernel.dk>
From:   =?UTF-8?Q?Andreas_Gr=C3=BCnbacher?= <andreas.gruenbacher@gmail.com>
Date:   Tue, 7 Jul 2020 13:38:01 +0200
Message-ID: <CAHpGcMJsrQXX4OQe6MqjyTt8BOLZw-y1ixdk76p_DsZONyEJcQ@mail.gmail.com>
Subject: Re: [PATCH 05/15] mm: allow read-ahead with IOCB_NOWAIT set
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Dave Chinner <david@fromorbit.com>, io-uring@vger.kernel.org,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Am Mi., 24. Juni 2020 um 18:48 Uhr schrieb Jens Axboe <axboe@kernel.dk>:
>
> On 6/24/20 10:41 AM, Matthew Wilcox wrote:
> > 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
>
> Yeah, that's probably better. How do we want to handle this? I've already
> got the other bits queued up. I can either add them to the series, or
> pull a branch that'll go into Linus as well.

Also note my conflicting patch that introduces a IOCB_NOIO flag for
fixing a gfs2 regression:

https://lore.kernel.org/linux-fsdevel/20200703095325.1491832-2-agruenba@redhat.com/

Thanks,
Andreas