| Message ID | 20191025072610.18526-2-mhocko@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: reduce /proc/pagetypeinfo ovehead | expand |
On 10/25/19 9:26 AM, 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 Cc: <stable@vger.kernel.org> > 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 >
On 25.10.19 09:26, 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 > 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 > Looks good too me (the ack list is already long enough :) )
On Fri, 25 Oct 2019 09:33:26 +0200 Vlastimil Babka <vbabka@suse.cz> wrote: > On 10/25/19 9:26 AM, 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 > > Cc: <stable@vger.kernel.org> As we don't really know how much damage this will cause, it would be nice to let it bake in mainline for a month or three before committing it to the -stable trees. But we don't have a process for that, apart from remembering to poke Greg at a suitable date. Oh well. I guess that if someone is truly harmed by this change, they can just chmod /proc/pagetypeinfo back to 0444.
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