From: Michal Hocko <mhocko@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Waiman Long <longman@redhat.com>
Cc: 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>,
David Rientjes <rientjes@google.com>
Subject: [PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users
Date: Fri, 25 Oct 2019 09:26:09 +0200 [thread overview]
Message-ID: <20191025072610.18526-2-mhocko@kernel.org> (raw)
In-Reply-To: <20191025072610.18526-1-mhocko@kernel.org>
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
Fixes: 467c996c1e19 ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo")
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/vmstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 6afc892a148a..4e885ecd44d1 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1972,7 +1972,7 @@ void __init init_mm_internals(void)
#endif
#ifdef CONFIG_PROC_FS
proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op);
- proc_create_seq("pagetypeinfo", 0444, NULL, &pagetypeinfo_op);
+ proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op);
proc_create_seq("vmstat", 0444, NULL, &vmstat_op);
proc_create_seq("zoneinfo", 0444, NULL, &zoneinfo_op);
#endif
--
2.20.1
next prev parent reply other threads:[~2019-10-25 7:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 7:26 [PATCH 0/2] mm: reduce /proc/pagetypeinfo ovehead Michal Hocko
2019-10-25 7:26 ` Michal Hocko [this message]
2019-10-25 7:33 ` [PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users Vlastimil Babka
2019-10-25 21:58 ` Andrew Morton
2019-10-25 8:18 ` David Hildenbrand
2019-10-25 7:26 ` [PATCH 2/2] mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo Michal Hocko
2019-10-25 7:35 ` Vlastimil Babka
2019-10-25 8:21 ` David Hildenbrand
2019-10-25 12:52 ` Rafael Aquini
2019-10-25 21:08 ` David Rientjes
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