Re: [PATCH 03/14] mm: Share the anon_vma ref counts between KSM andpage migration

From: Rik van Riel
Date: Tue Apr 06 2010 - 20:11:24 EST

On 04/06/2010 08:05 PM, Andrew Morton wrote:
On Fri, 2 Apr 2010 17:02:37 +0100
Mel Gorman<mel@xxxxxxxxx> wrote:

+#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)
+ /*
+ * The external_refcount is taken by either KSM or page migration
+ * to take a reference to an anon_vma when there is no
+ * guarantee that the vma of page tables will exist for
+ * the duration of the operation. A caller that takes
+ * the reference is responsible for clearing up the
+ * anon_vma if they are the last user on release
+ */
+ atomic_t external_refcount;


+ anonvma_external_refcount_init(anon_vma);

What a mouthful. Can we do s/external_//g?

For the function, sure.

However, I believe it would be good to keep the variable
inside the anon_vma as "external_refcount", because the
VMAs attached to the anon_vma take a reference by being
on the list (and leave the refcount alone).
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