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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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