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Date:   Wed, 23 Oct 2019 14:13:01 +0100
From:   Mel Gorman <mgorman@suse.de>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Waiman Long <longman@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.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>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>,
        Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal
 users
Message-ID: <20191023131301.GB28938@suse.de>
References: <20191023095607.GE3016@techsingularity.net>
 <20191023102737.32274-1-mhocko@kernel.org>
 <20191023102737.32274-2-mhocko@kernel.org>
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On Wed, Oct 23, 2019 at 12:27:36PM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> /proc/pagetypeinfo is a debugging tool to examine internal page
> allocator state wrt to fragmentation. It is not very useful for
> any other use so normal users really do not need to read this file.
> 
> Waiman Long has noticed that reading this file can have negative side
> effects because zone->lock is necessary for gathering data and that
> a) interferes with the page allocator and its users and b) can lead to
> hard lockups on large machines which have very long free_list.
> 
> Reduce both issues by simply not exporting the file to regular users.
> 
> Reported-by: Waiman Long <longman@redhat.com>
> Cc: stable
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs