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;
Message-ID: <9f6b707c69ceb34e3916b1d47f2e2fa6a4f025ab.camel@gmx.de>
Subject: Re: mlockall(MCL_CURRENT) blocking infinitely
From:   Robert Stupp <snazy@gmx.de>
Reply-To: snazy@snazy.de
To:     Josef Bacik <josef@toxicpanda.com>, Jan Kara <jack@suse.cz>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@kernel.org>,
        "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>
Date:   Wed, 06 Nov 2019 17:39:35 +0100
In-Reply-To: <20191106151429.swqtq2dt4uelhjzn@macbook-pro-91.dhcp.thefacebook.com>
References: <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>
         <20191106145608.ucvuwsuyijvkxz22@macbook-pro-91.dhcp.thefacebook.com>
         <20191106150524.GL16085@quack2.suse.cz>
         <20191106151429.swqtq2dt4uelhjzn@macbook-pro-91.dhcp.thefacebook.com>
Content-Type: multipart/mixed; boundary="=-tHCgSIlg3PheX7osEgF8"
User-Agent: Evolution 3.34.1-2 
MIME-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


--=-tHCgSIlg3PheX7osEgF8
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Wed, 2019-11-06 at 10:14 -0500, Josef Bacik wrote:
> On Wed, Nov 06, 2019 at 04:05:24PM +0100, Jan Kara wrote:
> > On Wed 06-11-19 09:56:09, Josef Bacik wrote:
> > I don't think this will work. AFAICS faultin_page() just checks
> > whether
> > 'nonblocking' is !=3D NULL but doesn't ever look at its value...
> > Honestly the
> > whole interface is rather weird like lots of things around gup().
> >
>
> Oh what the hell, yeah this is super bonkers.  The whole fault path
> probably
> should be cleaned up to handle retry better.  This will do the trick
> I think?

I tried the patch, and it seems to fix the `mlockall(MCL_CURRENT)`
issue for "my test.c".
However, shutdown & reboot are still broken - i.e. the console says
"Reached target reboot" and "hangs forever". Shutdown & reboot work
with __get_user_pages_locked(). No clue what the difference there is.

Anyway, I've captured three smaps outputs: from 5.0.21, from
5.3.9+"nonblocking patch", from 5.3.9+"__get_user_pages_locked". All
three look okay to me - although I don't completely understand why some
areas are not locked (-> "Locked: 0kB") - but "Locked" is always equal
to "Pss", so I assume that's fine?

>
> Josef
>
> diff --git a/mm/gup.c b/mm/gup.c
> index 8f236a335ae9..2468789298e6 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -628,7 +628,7 @@ static int faultin_page(struct task_struct *tsk,
> struct vm_area_struct *vma,
>  		fault_flags |=3D FAULT_FLAG_WRITE;
>  	if (*flags & FOLL_REMOTE)
>  		fault_flags |=3D FAULT_FLAG_REMOTE;
> -	if (nonblocking)
> +	if (nonblocking && *nonblocking !=3D 0)
>  		fault_flags |=3D FAULT_FLAG_ALLOW_RETRY;
>  	if (*flags & FOLL_NOWAIT)
>  		fault_flags |=3D FAULT_FLAG_ALLOW_RETRY |
> FAULT_FLAG_RETRY_NOWAIT;
> @@ -1237,6 +1237,7 @@ int __mm_populate(unsigned long start, unsigned
> long len, int ignore_errors)
>  	unsigned long end, nstart, nend;
>  	struct vm_area_struct *vma =3D NULL;
>  	int locked =3D 0;
> +	int nonblocking =3D 1;
>  	long ret =3D 0;
>
>  	end =3D start + len;
> @@ -1268,7 +1269,7 @@ int __mm_populate(unsigned long start, unsigned
> long len, int ignore_errors)
>  		 * double checks the vma flags, so that it won't mlock
> pages
>  		 * if the vma was already munlocked.
>  		 */
> -		ret =3D populate_vma_page_range(vma, nstart, nend,
> &locked);
> +		ret =3D populate_vma_page_range(vma, nstart, nend,
> &nonblocking);
>  		if (ret < 0) {
>  			if (ignore_errors) {
>  				ret =3D 0;
> @@ -1276,6 +1277,14 @@ int __mm_populate(unsigned long start,
> unsigned long len, int ignore_errors)
>  			}
>  			break;
>  		}
> +
> +		/*
> +		 * We dropped the mmap_sem, so we need to re-lock, and
> the next
> +		 * loop around we won't drop because nonblocking is now
> 0.
> +		 */
> +		if (!nonblocking)
> +			locked =3D 0;
> +
>  		nend =3D nstart + ret * PAGE_SIZE;
>  		ret =3D 0;
>  	}

--=-tHCgSIlg3PheX7osEgF8
Content-Type: application/gzip; name="smaps-5.0.21.txt.gz"
Content-Disposition: attachment; filename="smaps-5.0.21.txt.gz"
Content-Transfer-Encoding: base64
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--=-tHCgSIlg3PheX7osEgF8
Content-Type: application/gzip; name="smaps-add-nonblocking.txt.gz"
Content-Disposition: attachment; filename="smaps-add-nonblocking.txt.gz"
Content-Transfer-Encoding: base64
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--=-tHCgSIlg3PheX7osEgF8
Content-Type: application/gzip; name="smaps-get_user_pages_locked.txt.gz"
Content-Disposition: attachment; filename="smaps-get_user_pages_locked.txt.gz"
Content-Transfer-Encoding: base64
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--=-tHCgSIlg3PheX7osEgF8--