refcount_t type should be used instead of atomic_t when the variable is used as a reference counter. This is because the implementation of refcount_t can prevent overflows and detect possible use-after-free.
Signed-off-by: Yejune Deng <[email protected]> --- include/linux/rmap.h | 7 ++++--- mm/rmap.c | 14 +++++++------- 2 files changed, 11 insertions(+), 10 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index def5c62c93b3..0d6dfea7afa6 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -11,6 +11,7 @@ #include <linux/rwsem.h> #include <linux/memcontrol.h> #include <linux/highmem.h> +#include <linux/refcount.h> /* * The anon_vma heads a list of private "related" vmas, to scan if @@ -36,7 +37,7 @@ struct anon_vma { * the reference is responsible for clearing up the * anon_vma if they are the last user on release */ - atomic_t refcount; + refcount_t refcount; /* * Count of child anon_vmas and VMAs which points to this anon_vma. @@ -103,14 +104,14 @@ enum ttu_flags { #ifdef CONFIG_MMU static inline void get_anon_vma(struct anon_vma *anon_vma) { - atomic_inc(&anon_vma->refcount); + refcount_inc(&anon_vma->refcount); } 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)) + if (refcount_dec_and_test(&anon_vma->refcount)) __put_anon_vma(anon_vma); } diff --git a/mm/rmap.c b/mm/rmap.c index b0fc27e77d6d..6aea12f3ac5c 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -88,7 +88,7 @@ static inline struct anon_vma *anon_vma_alloc(void) anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); if (anon_vma) { - atomic_set(&anon_vma->refcount, 1); + refcount_set(&anon_vma->refcount, 1); anon_vma->degree = 1; /* Reference for first vma */ anon_vma->parent = anon_vma; /* @@ -103,7 +103,7 @@ static inline struct anon_vma *anon_vma_alloc(void) static inline void anon_vma_free(struct anon_vma *anon_vma) { - VM_BUG_ON(atomic_read(&anon_vma->refcount)); + VM_BUG_ON(refcount_read(&anon_vma->refcount)); /* * Synchronize against page_lock_anon_vma_read() such that @@ -445,7 +445,7 @@ static void anon_vma_ctor(void *data) struct anon_vma *anon_vma = data; init_rwsem(&anon_vma->rwsem); - atomic_set(&anon_vma->refcount, 0); + refcount_set(&anon_vma->refcount, 0); anon_vma->rb_root = RB_ROOT_CACHED; } @@ -495,7 +495,7 @@ struct anon_vma *page_get_anon_vma(struct page *page) goto out; anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); - if (!atomic_inc_not_zero(&anon_vma->refcount)) { + if (!refcount_inc_not_zero(&anon_vma->refcount)) { anon_vma = NULL; goto out; } @@ -554,7 +554,7 @@ struct anon_vma *page_lock_anon_vma_read(struct page *page) } /* trylock failed, we got to sleep */ - if (!atomic_inc_not_zero(&anon_vma->refcount)) { + if (!refcount_inc_not_zero(&anon_vma->refcount)) { anon_vma = NULL; goto out; } @@ -569,7 +569,7 @@ struct anon_vma *page_lock_anon_vma_read(struct page *page) rcu_read_unlock(); anon_vma_lock_read(anon_vma); - if (atomic_dec_and_test(&anon_vma->refcount)) { + if (refcount_dec_and_test(&anon_vma->refcount)) { /* * Oops, we held the last refcount, release the lock * and bail -- can't simply use put_anon_vma() because @@ -1810,7 +1810,7 @@ void __put_anon_vma(struct anon_vma *anon_vma) struct anon_vma *root = anon_vma->root; anon_vma_free(anon_vma); - if (root != anon_vma && atomic_dec_and_test(&root->refcount)) + if (root != anon_vma && refcount_dec_and_test(&root->refcount)) anon_vma_free(root); } -- 2.29.0
