On Fri 02-11-18 14:44:11, Janne Huttunen wrote: > Hi, > > The commit 1d90ca897 changed the type of the vm_numa_stat_diff > from s8 into u16. It also changed the associated BUILD_BUG_ON() > in need_update(), but didn't touch the memchr_inv() call after > it. Is the memchr_inv() call still supposed to cover the whole > array or am I just misreading the code? I guess you are not missing anything. We need something like diff --git a/mm/vmstat.c b/mm/vmstat.c index 6038ce593ce3..c42f01fbe964 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1829,10 +1829,10 @@ 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, sizeof(*p->vm_stat_diff) * NR_VM_ZONE_STAT_ITEMS)) 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, sizeof(p->vm_numa_stat_diff) * NR_VM_NUMA_STAT_ITEMS)) return true; #endif } sizeof(p->vm_numa_stat_diff) would be shorter but more fragile if we ever decide to change the type to be a pointer rather than a fixed arrasy. Care to send a full patch? -- Michal Hocko SUSE Labs
