diff options
Diffstat (limited to 'include/linux/radix-tree.h')
| -rw-r--r-- | include/linux/radix-tree.h | 38 |
1 files changed, 21 insertions, 17 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 430e4a8c138..b6116b4445c 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -26,28 +26,31 @@ #include <linux/rcupdate.h> /* - * A direct pointer (root->rnode pointing directly to a data item, - * rather than another radix_tree_node) is signalled by the low bit - * set in the root->rnode pointer. + * An indirect pointer (root->rnode pointing to a radix_tree_node, rather + * than a data item) is signalled by the low bit set in the root->rnode + * pointer. * - * In this case root->height is also NULL, but the direct pointer tests are - * needed for RCU lookups when root->height is unreliable. + * In this case root->height is > 0, but the indirect pointer tests are + * needed for RCU lookups (because root->height is unreliable). The only + * time callers need worry about this is when doing a lookup_slot under + * RCU. */ -#define RADIX_TREE_DIRECT_PTR 1 +#define RADIX_TREE_INDIRECT_PTR 1 +#define RADIX_TREE_RETRY ((void *)-1UL) -static inline void *radix_tree_ptr_to_direct(void *ptr) +static inline void *radix_tree_ptr_to_indirect(void *ptr) { - return (void *)((unsigned long)ptr | RADIX_TREE_DIRECT_PTR); + return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); } -static inline void *radix_tree_direct_to_ptr(void *ptr) +static inline void *radix_tree_indirect_to_ptr(void *ptr) { - return (void *)((unsigned long)ptr & ~RADIX_TREE_DIRECT_PTR); + return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); } -static inline int radix_tree_is_direct_ptr(void *ptr) +static inline int radix_tree_is_indirect_ptr(void *ptr) { - return (int)((unsigned long)ptr & RADIX_TREE_DIRECT_PTR); + return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); } /*** radix-tree API starts here ***/ @@ -130,7 +133,10 @@ do { \ */ static inline void *radix_tree_deref_slot(void **pslot) { - return radix_tree_direct_to_ptr(*pslot); + void *ret = *pslot; + if (unlikely(radix_tree_is_indirect_ptr(ret))) + ret = RADIX_TREE_RETRY; + return ret; } /** * radix_tree_replace_slot - replace item in a slot @@ -142,10 +148,8 @@ static inline void *radix_tree_deref_slot(void **pslot) */ static inline void radix_tree_replace_slot(void **pslot, void *item) { - BUG_ON(radix_tree_is_direct_ptr(item)); - rcu_assign_pointer(*pslot, - (void *)((unsigned long)item | - ((unsigned long)*pslot & RADIX_TREE_DIRECT_PTR))); + BUG_ON(radix_tree_is_indirect_ptr(item)); + rcu_assign_pointer(*pslot, item); } int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); |