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Commit 83813267 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

mm: move anon_vma ref out from under CONFIG_foo 



We need the anon_vma refcount unconditionally to simplify the anon_vma
lifetime rules.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9e60109f

include/linux/rmap.h

+4 −36
Original line number Diff line number Diff line
@@ -27,18 +27,15 @@ 
struct anon_vma {

	struct anon_vma *root;	/* Root of this anon_vma tree */

	spinlock_t lock;	/* Serialize access to vma list */

#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

	 * The refcount is taken on 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;

#endif

	atomic_t refcount;



	/*

	 * NOTE: the LSB of the head.next is set by

	 * mm_take_all_locks() _after_ taking the above lock. So the
@@ -71,41 +68,12 @@ struct anon_vma_chain { 
};



#ifdef CONFIG_MMU

#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)

static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)

{

	atomic_set(&anon_vma->external_refcount, 0);

}



static inline int anonvma_external_refcount(struct anon_vma *anon_vma)

{

	return atomic_read(&anon_vma->external_refcount);

}



static inline void get_anon_vma(struct anon_vma *anon_vma)

{

	atomic_inc(&anon_vma->external_refcount);

	atomic_inc(&anon_vma->refcount);

}



void put_anon_vma(struct anon_vma *);

#else

static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)

{

}



static inline int anonvma_external_refcount(struct anon_vma *anon_vma)

{

	return 0;

}



static inline void get_anon_vma(struct anon_vma *anon_vma)

{

}



static inline void put_anon_vma(struct anon_vma *anon_vma)

{

}

#endif /* CONFIG_KSM */



static inline struct anon_vma *page_anon_vma(struct page *page)

{

mm/rmap.c

+6 −8
Original line number Diff line number Diff line
@@ -272,7 +272,7 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain) 
	list_del(&anon_vma_chain->same_anon_vma);



	/* We must garbage collect the anon_vma if it's empty */

	empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);

	empty = list_empty(&anon_vma->head) && !atomic_read(&anon_vma->refcount);

	anon_vma_unlock(anon_vma);



	if (empty) {
@@ -303,7 +303,7 @@ static void anon_vma_ctor(void *data) 
	struct anon_vma *anon_vma = data;



	spin_lock_init(&anon_vma->lock);

	anonvma_external_refcount_init(anon_vma);

	atomic_set(&anon_vma->refcount, 0);

	INIT_LIST_HEAD(&anon_vma->head);

}
@@ -1486,7 +1486,6 @@ int try_to_munlock(struct page *page) 
		return try_to_unmap_file(page, TTU_MUNLOCK);

}



#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)

/*

 * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root

 * if necessary.  Be careful to do all the tests under the lock.  Once
@@ -1495,8 +1494,8 @@ int try_to_munlock(struct page *page) 
 */

void put_anon_vma(struct anon_vma *anon_vma)

{

	BUG_ON(atomic_read(&anon_vma->external_refcount) <= 0);

	if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) {

	BUG_ON(atomic_read(&anon_vma->refcount) <= 0);

	if (atomic_dec_and_lock(&anon_vma->refcount, &anon_vma->root->lock)) {

		struct anon_vma *root = anon_vma->root;

		int empty = list_empty(&anon_vma->head);

		int last_root_user = 0;
@@ -1507,8 +1506,8 @@ void put_anon_vma(struct anon_vma *anon_vma) 
		 * the refcount on the root and check if we need to free it.

		 */

		if (empty && anon_vma != root) {

			BUG_ON(atomic_read(&root->external_refcount) <= 0);

			last_root_user = atomic_dec_and_test(&root->external_refcount);

			BUG_ON(atomic_read(&root->refcount) <= 0);

			last_root_user = atomic_dec_and_test(&root->refcount);

			root_empty = list_empty(&root->head);

		}

		anon_vma_unlock(anon_vma);
@@ -1520,7 +1519,6 @@ void put_anon_vma(struct anon_vma *anon_vma) 
		}

	}

}

#endif



#ifdef CONFIG_MIGRATION

/*