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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: 1d90ca897c ("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>
This commit is contained in:
Janne Huttunen 2018-11-16 15:08:32 -08:00 committed by Linus Torvalds
parent 78179556e7
commit 13c9aaf7fa
1 changed files with 4 additions and 3 deletions
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7
mm/vmstat.c
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@ -1827,12 +1827,13 @@ static bool need_update(int cpu)
/* /*
* The fast way of checking if there are any vmstat diffs. * 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; return true;
#ifdef CONFIG_NUMA #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; return true;
#endif #endif
} }