Commit 13c9aaf7 authored Nov 16, 2018 by Janne Huttunen Committed by Linus Torvalds Nov 18, 2018

mm/vmstat.c: fix NUMA statistics updates

Scan through the whole array to see if an update is needed.  While we're
at it, use sizeof() to be safe against any possible type changes in the
future.

The bug here is that we wouldn't sync per-cpu counters into global ones
if there was an update of numa_stats for higher cpus.  Highly
theoretical one though because it is much more probable that zone_stats
are updated so we would refresh anyway.  So I wouldn't bother to mark
this for stable, yet something nice to fix.

[mhocko@suse.com: changelog enhancement]
Link: http://lkml.kernel.org/r/1541601517-17282-1-git-send-email-janne.huttunen@nokia.com


Fixes: 1d90ca89 ("mm: update NUMA counter threshold size")
Signed-off-by: Janne Huttunen <janne.huttunen@nokia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 78179556

mm/vmstat.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1827,12 +1827,13 @@ static bool need_update(int cpu)

		/*
		* The fast way of checking if there are any vmstat diffs.
		* This works because the diffs are byte sized items.
		*/
		if (memchr_inv(p->vm_stat_diff, 0, NR_VM_ZONE_STAT_ITEMS))
		if (memchr_inv(p->vm_stat_diff, 0, NR_VM_ZONE_STAT_ITEMS *
		sizeof(p->vm_stat_diff[0])))
		return true;
		#ifdef CONFIG_NUMA
		if (memchr_inv(p->vm_numa_stat_diff, 0, NR_VM_NUMA_STAT_ITEMS))
		if (memchr_inv(p->vm_numa_stat_diff, 0, NR_VM_NUMA_STAT_ITEMS *
		sizeof(p->vm_numa_stat_diff[0])))
		return true;
		#endif
		}

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