mm: migration: share the anon_vma ref counts between KSM and page migration
For clarity of review, KSM and page migration have separate refcounts on the anon_vma. While clear, this is a waste of memory. This patch gets KSM and page migration to share their toys in a spirit of harmony. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds

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3f6c82728f
commit
7f60c214fd
@@ -601,7 +601,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
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rcu_read_lock();
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rcu_locked = 1;
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anon_vma = page_anon_vma(page);
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atomic_inc(&anon_vma->migrate_refcount);
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atomic_inc(&anon_vma->external_refcount);
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}
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/*
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@@ -643,7 +643,7 @@ skip_unmap:
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rcu_unlock:
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/* Drop an anon_vma reference if we took one */
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if (anon_vma && atomic_dec_and_lock(&anon_vma->migrate_refcount, &anon_vma->lock)) {
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if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {
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int empty = list_empty(&anon_vma->head);
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spin_unlock(&anon_vma->lock);
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if (empty)
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