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mm: add rss counters consistency check

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Warn about non-zero rss counters at final mmdrop.

This check will prevent reoccurences of bugs such as that fixed in "mm:
fix rss count leakage during migration".

I didn't hide this check under CONFIG_VM_DEBUG because it rather small and
rss counters cover whole page-table management, so this is a good
invariant.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2012-03-21 16:33:48 -07:00 committed by Linus Torvalds
parent dc3f21eade
commit c3f0327f8e
1 changed files with 18 additions and 3 deletions
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21
kernel/fork.c
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@ -511,6 +511,23 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
return NULL;
}
static void check_mm(struct mm_struct *mm)
{
int i;
for (i = 0; i < NR_MM_COUNTERS; i++) {
long x = atomic_long_read(&mm->rss_stat.count[i]);
if (unlikely(x))
printk(KERN_ALERT "BUG: Bad rss-counter state "
"mm:%p idx:%d val:%ld\n", mm, i, x);
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
VM_BUG_ON(mm->pmd_huge_pte);
#endif
}
/*
* Allocate and initialize an mm_struct.
*/
@ -538,9 +555,7 @@ void __mmdrop(struct mm_struct *mm)
mm_free_pgd(mm);
destroy_context(mm);
mmu_notifier_mm_destroy(mm);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
VM_BUG_ON(mm->pmd_huge_pte);
#endif
check_mm(mm);
free_mm(mm);
}
EXPORT_SYMBOL_GPL(__mmdrop);