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Commit c3f0327f authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds
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mm: add rss counters consistency check 



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: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dc3f21ea

kernel/fork.c

+18 −3
Original line number Diff line number Diff line
@@ -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);