From 9e60109f125013b6c571f399a15a8b0fe1ffa4e6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 22 Mar 2011 16:32:46 -0700 Subject: mm: rename drop_anon_vma() to put_anon_vma() The normal code pattern used in the kernel is: get/put. Signed-off-by: Peter Zijlstra Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Hugh Dickins Reviewed-by: Rik van Riel Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rmap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/rmap.h') diff --git a/include/linux/rmap.h b/include/linux/rmap.h index e9fd04ca1e5..b9b23ddca63 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -87,7 +87,7 @@ static inline void get_anon_vma(struct anon_vma *anon_vma) atomic_inc(&anon_vma->external_refcount); } -void drop_anon_vma(struct anon_vma *); +void put_anon_vma(struct anon_vma *); #else static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma) { @@ -102,7 +102,7 @@ static inline void get_anon_vma(struct anon_vma *anon_vma) { } -static inline void drop_anon_vma(struct anon_vma *anon_vma) +static inline void put_anon_vma(struct anon_vma *anon_vma) { } #endif /* CONFIG_KSM */ -- cgit v1.2.3-70-g09d2 From 83813267c699ab11cc65a6d9d0f42db42f0862b3 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 22 Mar 2011 16:32:48 -0700 Subject: 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: Peter Zijlstra Acked-by: Mel Gorman Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Hugh Dickins Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rmap.h | 40 ++++------------------------------------ mm/rmap.c | 14 ++++++-------- 2 files changed, 10 insertions(+), 44 deletions(-) (limited to 'include/linux/rmap.h') diff --git a/include/linux/rmap.h b/include/linux/rmap.h index b9b23ddca63..fd56111a52c 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -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) { diff --git a/mm/rmap.c b/mm/rmap.c index ad416afb206..873cd9ef912 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -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 /* -- cgit v1.2.3-70-g09d2 From 01d8b20dec5f4019283e244aba50ba86fe6ead6e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 22 Mar 2011 16:32:49 -0700 Subject: mm: simplify anon_vma refcounts This patch changes the anon_vma refcount to be 0 when the object is free. It does this by adding 1 ref to being in use in the anon_vma structure (iow. the anon_vma->head list is not empty). This allows a simpler release scheme without having to check both the refcount and the list as well as avoids taking a ref for each entry on the list. Signed-off-by: Peter Zijlstra Reviewed-by: KAMEZAWA Hiroyuki Acked-by: Hugh Dickins Acked-by: Mel Gorman Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rmap.h | 11 ++++++-- mm/rmap.c | 76 +++++++++++++++++++--------------------------------- 2 files changed, 37 insertions(+), 50 deletions(-) (limited to 'include/linux/rmap.h') diff --git a/include/linux/rmap.h b/include/linux/rmap.h index fd56111a52c..830e65dc01e 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -73,7 +73,13 @@ static inline void get_anon_vma(struct anon_vma *anon_vma) atomic_inc(&anon_vma->refcount); } -void put_anon_vma(struct anon_vma *); +void __put_anon_vma(struct anon_vma *anon_vma); + +static inline void put_anon_vma(struct anon_vma *anon_vma) +{ + if (atomic_dec_and_test(&anon_vma->refcount)) + __put_anon_vma(anon_vma); +} static inline struct anon_vma *page_anon_vma(struct page *page) { @@ -116,7 +122,6 @@ void unlink_anon_vmas(struct vm_area_struct *); int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); void __anon_vma_link(struct vm_area_struct *); -void anon_vma_free(struct anon_vma *); static inline void anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next) @@ -125,6 +130,8 @@ static inline void anon_vma_merge(struct vm_area_struct *vma, unlink_anon_vmas(next); } +struct anon_vma *page_get_anon_vma(struct page *page); + /* * rmap interfaces called when adding or removing pte of page */ diff --git a/mm/rmap.c b/mm/rmap.c index 873cd9ef912..4a8e99a0fb9 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -67,11 +67,24 @@ static struct kmem_cache *anon_vma_chain_cachep; static inline struct anon_vma *anon_vma_alloc(void) { - return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); + struct anon_vma *anon_vma; + + anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); + if (anon_vma) { + atomic_set(&anon_vma->refcount, 1); + /* + * Initialise the anon_vma root to point to itself. If called + * from fork, the root will be reset to the parents anon_vma. + */ + anon_vma->root = anon_vma; + } + + return anon_vma; } -void anon_vma_free(struct anon_vma *anon_vma) +static inline void anon_vma_free(struct anon_vma *anon_vma) { + VM_BUG_ON(atomic_read(&anon_vma->refcount)); kmem_cache_free(anon_vma_cachep, anon_vma); } @@ -133,11 +146,6 @@ int anon_vma_prepare(struct vm_area_struct *vma) if (unlikely(!anon_vma)) goto out_enomem_free_avc; allocated = anon_vma; - /* - * This VMA had no anon_vma yet. This anon_vma is - * the root of any anon_vma tree that might form. - */ - anon_vma->root = anon_vma; } anon_vma_lock(anon_vma); @@ -156,7 +164,7 @@ int anon_vma_prepare(struct vm_area_struct *vma) anon_vma_unlock(anon_vma); if (unlikely(allocated)) - anon_vma_free(allocated); + put_anon_vma(allocated); if (unlikely(avc)) anon_vma_chain_free(avc); } @@ -241,9 +249,9 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) */ anon_vma->root = pvma->anon_vma->root; /* - * With KSM refcounts, an anon_vma can stay around longer than the - * process it belongs to. The root anon_vma needs to be pinned - * until this anon_vma is freed, because the lock lives in the root. + * With refcounts, an anon_vma can stay around longer than the + * process it belongs to. The root anon_vma needs to be pinned until + * this anon_vma is freed, because the lock lives in the root. */ get_anon_vma(anon_vma->root); /* Mark this anon_vma as the one where our new (COWed) pages go. */ @@ -253,7 +261,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) return 0; out_error_free_anon_vma: - anon_vma_free(anon_vma); + put_anon_vma(anon_vma); out_error: unlink_anon_vmas(vma); return -ENOMEM; @@ -272,15 +280,11 @@ 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) && !atomic_read(&anon_vma->refcount); + empty = list_empty(&anon_vma->head); anon_vma_unlock(anon_vma); - if (empty) { - /* We no longer need the root anon_vma */ - if (anon_vma->root != anon_vma) - put_anon_vma(anon_vma->root); - anon_vma_free(anon_vma); - } + if (empty) + put_anon_vma(anon_vma); } void unlink_anon_vmas(struct vm_area_struct *vma) @@ -1486,38 +1490,14 @@ int try_to_munlock(struct page *page) return try_to_unmap_file(page, TTU_MUNLOCK); } -/* - * 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 - * we know we are the last user, nobody else can get a reference and we - * can do the freeing without the lock. - */ -void put_anon_vma(struct anon_vma *anon_vma) +void __put_anon_vma(struct anon_vma *anon_vma) { - 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; - int root_empty = 0; + struct anon_vma *root = anon_vma->root; - /* - * The refcount on a non-root anon_vma got dropped. Drop - * the refcount on the root and check if we need to free it. - */ - if (empty && anon_vma != root) { - 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); + if (root != anon_vma && atomic_dec_and_test(&root->refcount)) + anon_vma_free(root); - if (empty) { - anon_vma_free(anon_vma); - if (root_empty && last_root_user) - anon_vma_free(root); - } - } + anon_vma_free(anon_vma); } #ifdef CONFIG_MIGRATION -- cgit v1.2.3-70-g09d2