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authorKonstantin Khlebnikov <khlebnikov@openvz.org>2012-03-21 16:33:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-21 17:54:55 -0700
commitc3f0327f8e9d7a503f0d64573c311eddd61f197d (patch)
treeebc59003d3bef08dd41d073eced2b53970e13662 /kernel/fork.c
parentdc3f21eadeea6d9898271ff32d35d5e00c6872ea (diff)
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>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c21
1 files changed, 18 insertions, 3 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index c4f38a84943..a9e99f3c18e 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);