From: Andrew Morton <akpm@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: Qian Cai <cai@lca.pw>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>, Roman Gushchin <guro@fb.com>,
Vlastimil Babka <vbabka@suse.cz>,
Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
Jann Horn <jannh@google.com>, Song Liu <songliubraving@fb.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rafael Aquini <aquini@redhat.com>
Subject: Re: [PATCH] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo
Date: Wed, 23 Oct 2019 15:30:40 -0700 [thread overview]
Message-ID: <20191023153040.c7fff4bc7c86ed605fc4667f@linux-foundation.org> (raw)
In-Reply-To: <a4398f60-c07e-8fa9-c26d-3b8f688e65a1@redhat.com>
On Wed, 23 Oct 2019 11:01:04 -0400 Waiman Long <longman@redhat.com> wrote:
> On 10/23/19 10:48 AM, Qian Cai wrote:
> >>> this still isn't a bulletproof fix. Maybe just terminate the list
> >>> walk if freecount reaches 1024. Would anyone really care?
> >>>
> >>> Sigh. I wonder if anyone really uses this thing for anything
> >>> important. Can we just remove it all?
> >>>
> >> Removing it will be a breakage of kernel API.
> > Who cares about breaking this part of the API that essentially nobody will use
> > this file?
> >
> There are certainly tools that use /proc/pagetypeinfo and this is how
> the problem is found. I am not against removing it, but we have to be
> careful and deprecate it in way that minimize user impact.
Yes, removing things is hard. One approach is to add printk_once(this
is going away, please email us if you use it) then wait a few years.
Backport that one-liner into -stable kernels to hopefully speed up the
process.
Meanwhile, we need to fix the DoS opportunity. How about my suggestion
that we limit the count to 1024, see if anyone notices? I bet they
don't!
next prev parent reply other threads:[~2019-10-23 22:30 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 16:21 [PATCH] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo Waiman Long
2019-10-22 16:57 ` Michal Hocko
2019-10-22 18:00 ` Waiman Long
2019-10-22 18:40 ` Waiman Long
2019-10-23 0:52 ` David Rientjes
2019-10-23 8:31 ` Mel Gorman
2019-10-23 9:04 ` Michal Hocko
2019-10-23 9:56 ` Mel Gorman
2019-10-23 10:27 ` [RFC PATCH 0/2] " Michal Hocko
2019-10-23 10:27 ` [RFC PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users Michal Hocko
2019-10-23 13:13 ` Mel Gorman
2019-10-23 13:27 ` Vlastimil Babka
2019-10-23 14:52 ` Waiman Long
2019-10-23 15:10 ` Rafael Aquini
2019-10-23 16:15 ` Vlastimil Babka
2019-10-24 19:01 ` David Rientjes
2019-10-23 10:27 ` [RFC PATCH 2/2] mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo Michal Hocko
2019-10-23 13:15 ` Mel Gorman
2019-10-23 13:32 ` Vlastimil Babka
2019-10-23 13:37 ` Michal Hocko
2019-10-23 13:48 ` Vlastimil Babka
2019-10-23 14:31 ` Michal Hocko
2019-10-23 16:20 ` Vlastimil Babka
2019-10-23 13:46 ` Rafael Aquini
2019-10-23 14:56 ` Waiman Long
2019-10-23 15:21 ` Waiman Long
2019-10-23 16:10 ` Michal Hocko
2019-10-23 16:17 ` Waiman Long
2019-10-23 16:21 ` Waiman Long
2019-10-23 16:15 ` Vlastimil Babka
2019-10-23 16:41 ` Michal Hocko
2019-10-23 16:47 ` Waiman Long
2019-10-23 17:34 ` [PATCH 1/2] mm, vmstat: Release zone lock more frequently when reading /proc/pagetypeinfo Waiman Long
2019-10-23 18:01 ` Michal Hocko
2019-10-23 18:14 ` Waiman Long
2019-10-23 20:02 ` Michal Hocko
2019-10-23 17:34 ` [PATCH 2/2] mm, vmstat: List total free blocks for each order in /proc/pagetypeinfo Waiman Long
2019-10-23 18:02 ` Michal Hocko
2019-10-23 18:07 ` Waiman Long
2019-10-24 8:20 ` [RFC PATCH 0/2] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo Michal Hocko
2019-10-24 16:16 ` Waiman Long
2019-10-23 12:42 ` [PATCH] " Qian Cai
2019-10-23 13:25 ` Vlastimil Babka
2019-10-22 21:59 ` Andrew Morton
2019-10-23 6:15 ` Michal Hocko
2019-10-23 14:30 ` Waiman Long
2019-10-23 14:48 ` Qian Cai
2019-10-23 15:01 ` Waiman Long
2019-10-23 15:05 ` Qian Cai
2019-10-23 22:30 ` Andrew Morton [this message]
2019-10-24 5:33 ` Qian Cai
2019-10-24 7:42 ` Michal Hocko
2019-10-24 11:11 ` Qian Cai
2019-10-24 13:38 ` Michal Hocko
2019-10-24 14:55 ` Qian Cai
2019-10-24 3:33 ` Feng Tang
2019-10-24 4:34 ` Qian Cai
2019-10-24 5:34 ` Feng Tang
2019-10-24 10:51 ` Qian Cai
2019-10-25 1:38 ` Feng Tang
2019-10-23 15:03 ` Rafael Aquini
2019-10-23 15:51 ` Qian Cai
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