diff options
Diffstat (limited to 'include/linux/radix-tree.h')
| -rw-r--r-- | include/linux/radix-tree.h | 30 |
1 files changed, 13 insertions, 17 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index c0d223cfac00..c8cc879046c7 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -29,20 +29,16 @@ #include <linux/rcupdate.h> /* - * 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 > 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. - * - * Indirect pointer in fact is also used to tag the last pointer of a node - * when it is shrunk, before we rcu free the node. See shrink code for - * details. + * Entries in the radix tree have the low bit set if they refer to a + * radix_tree_node. If the low bit is clear then the entry is user data. + * + * We also use the low bit to indicate that the slot will be freed in the + * next RCU idle period, and users need to re-walk the tree to find the + * new slot for the index that they were looking for. See the comment in + * radix_tree_shrink() for details. */ -#define RADIX_TREE_INDIRECT_PTR 1 +#define RADIX_TREE_INTERNAL_NODE 1 + /* * A common use of the radix tree is to store pointers to struct pages; * but shmem/tmpfs needs also to store swap entries in the same tree: @@ -63,7 +59,7 @@ static inline int radix_tree_is_indirect_ptr(void *ptr) { - return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR); + return (int)((unsigned long)ptr & RADIX_TREE_INTERNAL_NODE); } /*** radix-tree API starts here ***/ @@ -228,7 +224,7 @@ static inline void *radix_tree_deref_slot_protected(void **pslot, */ static inline int radix_tree_deref_retry(void *arg) { - return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR); + return unlikely(radix_tree_is_indirect_ptr(arg)); } /** @@ -250,7 +246,7 @@ static inline int radix_tree_exceptional_entry(void *arg) static inline int radix_tree_exception(void *arg) { return unlikely((unsigned long)arg & - (RADIX_TREE_INDIRECT_PTR | RADIX_TREE_EXCEPTIONAL_ENTRY)); + (RADIX_TREE_INTERNAL_NODE | RADIX_TREE_EXCEPTIONAL_ENTRY)); } /** @@ -448,7 +444,7 @@ radix_tree_chunk_size(struct radix_tree_iter *iter) static inline void *indirect_to_ptr(void *ptr) { - return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); + return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE); } /** |