From c3f0327f8e9d7a503f0d64573c311eddd61f197d Mon Sep 17 00:00:00 2001
From: Konstantin Khlebnikov <khlebnikov@openvz.org>
Date: Wed, 21 Mar 2012 16:33:48 -0700
Subject: [PATCH] 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: 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 | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index c4f38a849436d..a9e99f3c18e06 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -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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