Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 6 Nov 2019 15:35:37 +0100
From:   Jan Kara <jack@suse.cz>
To:     snazy@snazy.de
Cc:     Jan Kara <jack@suse.cz>, Johannes Weiner <hannes@cmpxchg.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@kernel.org>,
        Josef Bacik <josef@toxicpanda.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Randy Dunlap <rdunlap@infradead.org>,
        linux-kernel@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Potyra, Stefan" <Stefan.Potyra@elektrobit.com>
Subject: Re: mlockall(MCL_CURRENT) blocking infinitely
Message-ID: <20191106143537.GI16085@quack2.suse.cz>
References: <20191025132700.GJ17610@dhcp22.suse.cz>
 <707b72c6dac76c534dcce60830fa300c44f53404.camel@gmx.de>
 <20191025135749.GK17610@dhcp22.suse.cz>
 <20191025140029.GL17610@dhcp22.suse.cz>
 <c2505804fda5326acf76b2be0155d558e5481fb5.camel@gmx.de>
 <fa6599459300c61da6348cdfd0cfda79e1c17a7a.camel@gmx.de>
 <ad13f479-3fda-b55a-d311-ef3914fbe649@suse.cz>
 <20191105182211.GA33242@cmpxchg.org>
 <20191106120315.GF16085@quack2.suse.cz>
 <4edf4dea97f6c1e3c7d4fed0e12c3dc6dff7575f.camel@gmx.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4edf4dea97f6c1e3c7d4fed0e12c3dc6dff7575f.camel@gmx.de>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed 06-11-19 14:45:43, Robert Stupp wrote:
> On Wed, 2019-11-06 at 13:03 +0100, Jan Kara wrote:
> > On Tue 05-11-19 13:22:11, Johannes Weiner wrote:
> > > What I don't quite understand yet is why the fault path doesn't
> > > make
> > > progress eventually. We must drop the mmap_sem without changing the
> > > state in any way. How can we keep looping on the same page?
> >
> > That may be a slight suboptimality with Josef's patches. If the page
> > is marked as PageReadahead, we always drop mmap_sem if we can and
> > start
> > readahead without checking whether that makes sense or not in
> > do_async_mmap_readahead(). OTOH page_cache_async_readahead() then
> > clears
> > PageReadahead so the only way how I can see we could loop like this
> > is when
> > file->ra->ra_pages is 0. Not sure if that's what's happening through.
> > We'd
> > need to find which of the paths in filemap_fault() calls
> > maybe_unlock_mmap_for_io() to tell more.
> 
> Yes, ra_pages==0

OK, thanks for confirmation!

> 5637e22a2000-5637e22a3000 r--p 00000000 103:02 49172550                  /home/snazy/devel/misc/zzz/test

What kind of device & fs does your /home stay on? I don't recognize the major
number...

							Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR