mm: add rss counters consistency check (c3f0327f) · Commits · 戴 / test

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>

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);

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