| Message ID | 1541601517-17282-1-git-send-email-janne.huttunen@nokia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: fix NUMA statistics updates | expand |
[CC Andrew] On Wed 07-11-18 16:38:37, Janne Huttunen wrote: > 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. > > Fixes: 1d90ca897cb0 ("mm: update NUMA counter threshold size") > Signed-off-by: Janne Huttunen <janne.huttunen@nokia.com> Acked-by: Michal Hocko <mhocko@suse.com> Feel free to use the explanation below to answer what is the runtime effect of the patch ;) > --- > Compile tested only! I don't know what error (if any) only scanning > half of the array causes, so I cannot verify that this patch actually > fixes it. 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. Thanks > mm/vmstat.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 7878da7..eca984d 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -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 > } > -- > 2.5.5
diff --git a/mm/vmstat.c b/mm/vmstat.c index 7878da7..eca984d 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -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 }
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. Fixes: 1d90ca897cb0 ("mm: update NUMA counter threshold size") Signed-off-by: Janne Huttunen <janne.huttunen@nokia.com> --- Compile tested only! I don't know what error (if any) only scanning half of the array causes, so I cannot verify that this patch actually fixes it. mm/vmstat.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)