The patch titled
Subject: mm, vmstat: hide /proc/pagetypeinfo from normal users
has been added to the -mm tree. Its filename is
mm-vmstat-hide-proc-pagetypeinfo-from-normal-users.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-vmstat-hide-proc-pagetypeinfo-from-normal-users.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-vmstat-hide-proc-pagetypeinfo-from-normal-users.patch
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From: Michal Hocko <mhocko@xxxxxxxx>
Subject: mm, vmstat: hide /proc/pagetypeinfo from normal users
/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.
Link: http://lkml.kernel.org/r/20191025072610.18526-2-mhocko@xxxxxxxxxx
Fixes: 467c996c1e19 ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo")
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reported-by: Waiman Long <longman@xxxxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Acked-by: Rafael Aquini <aquini@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmstat.c~mm-vmstat-hide-proc-pagetypeinfo-from-normal-users
+++ a/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
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
mm-vmstat-hide-proc-pagetypeinfo-from-normal-users.patch
mm-vmstat-reduce-zone-lock-holding-time-by-proc-pagetypeinfo.patch
