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-rw-r--r--include/linux/radix-tree.h39
1 files changed, 23 insertions, 16 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index a39cbed9ee17..ab2baa5c4884 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -34,19 +34,13 @@
* 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.
*/
#define RADIX_TREE_INDIRECT_PTR 1
-#define RADIX_TREE_RETRY ((void *)-1UL)
-
-static inline void *radix_tree_ptr_to_indirect(void *ptr)
-{
- return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
-}
-static inline void *radix_tree_indirect_to_ptr(void *ptr)
-{
- return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
-}
#define radix_tree_indirect_to_ptr(ptr) \
radix_tree_indirect_to_ptr((void __force *)(ptr))
@@ -140,16 +134,29 @@ do { \
* removed.
*
* For use with radix_tree_lookup_slot(). Caller must hold tree at least read
- * locked across slot lookup and dereference. More likely, will be used with
- * radix_tree_replace_slot(), as well, so caller will hold tree write locked.
+ * locked across slot lookup and dereference. Not required if write lock is
+ * held (ie. items cannot be concurrently inserted).
+ *
+ * radix_tree_deref_retry must be used to confirm validity of the pointer if
+ * only the read lock is held.
*/
static inline void *radix_tree_deref_slot(void **pslot)
{
- void *ret = rcu_dereference(*pslot);
- if (unlikely(radix_tree_is_indirect_ptr(ret)))
- ret = RADIX_TREE_RETRY;
- return ret;
+ return rcu_dereference(*pslot);
}
+
+/**
+ * radix_tree_deref_retry - check radix_tree_deref_slot
+ * @arg: pointer returned by radix_tree_deref_slot
+ * Returns: 0 if retry is not required, otherwise retry is required
+ *
+ * radix_tree_deref_retry must be used with radix_tree_deref_slot.
+ */
+static inline int radix_tree_deref_retry(void *arg)
+{
+ return unlikely((unsigned long)arg & RADIX_TREE_INDIRECT_PTR);
+}
+
/**
* radix_tree_replace_slot - replace item in a slot
* @pslot: pointer to slot, returned by radix_tree_lookup_slot