Merge branch 'for-linus' of git://git.kernel.dk/linux-block

[deliverable/linux.git] / include / linux / radix-tree.h

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 11c8e7cc392007811b5d673972af08056f9098a6..cb4b7e8cee81a40cbfedf0a781c7f701ed9e6ee0 100644 (file)
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -29,37 +29,37 @@
 #include <linux/rcupdate.h>
 
 /*
- * 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.
+ * The bottom two bits of the slot determine how the remaining bits in the
+ * slot are interpreted:
+ *
+ * 00 - data pointer
+ * 01 - internal entry
+ * 10 - exceptional entry
+ * 11 - locked exceptional entry
+ *
+ * The internal entry may be a pointer to the next level in the tree, a
+ * sibling entry, or an indicator that the entry in this slot has been moved
+ * to another location in the tree and the lookup should be restarted.  While
+ * NULL fits the 'data pointer' pattern, it means that there is no entry in
+ * the tree for this index (no matter what level of the tree it is found at).
+ * This means that you cannot store NULL in the tree as a value for the index.
  */
-#define RADIX_TREE_INTERNAL_NODE       1
+#define RADIX_TREE_ENTRY_MASK          3UL
+#define RADIX_TREE_INTERNAL_NODE       1UL
 
 /*
- * 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:
- * those are marked as exceptional entries to distinguish them.
+ * Most users of the radix tree store pointers but shmem/tmpfs stores swap
+ * entries in the same tree.  They are marked as exceptional entries to
+ * distinguish them from pointers to struct page.
  * EXCEPTIONAL_ENTRY tests the bit, EXCEPTIONAL_SHIFT shifts content past it.
  */
 #define RADIX_TREE_EXCEPTIONAL_ENTRY   2
 #define RADIX_TREE_EXCEPTIONAL_SHIFT   2
 
-#define RADIX_DAX_MASK 0xf
-#define RADIX_DAX_SHIFT        4
-#define RADIX_DAX_PTE  (0x4 | RADIX_TREE_EXCEPTIONAL_ENTRY)
-#define RADIX_DAX_PMD  (0x8 | RADIX_TREE_EXCEPTIONAL_ENTRY)
-#define RADIX_DAX_TYPE(entry) ((unsigned long)entry & RADIX_DAX_MASK)
-#define RADIX_DAX_SECTOR(entry) (((unsigned long)entry >> RADIX_DAX_SHIFT))
-#define RADIX_DAX_ENTRY(sector, pmd) ((void *)((unsigned long)sector << \
-               RADIX_DAX_SHIFT | (pmd ? RADIX_DAX_PMD : RADIX_DAX_PTE)))
-
-static inline int radix_tree_is_internal_node(void *ptr)
+static inline bool radix_tree_is_internal_node(void *ptr)
 {
-       return (int)((unsigned long)ptr & RADIX_TREE_INTERNAL_NODE);
+       return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
+                               RADIX_TREE_INTERNAL_NODE;
 }
 
 /*** radix-tree API starts here ***/
@@ -245,8 +245,7 @@ static inline int radix_tree_exceptional_entry(void *arg)
  */
 static inline int radix_tree_exception(void *arg)
 {
-       return unlikely((unsigned long)arg &
-               (RADIX_TREE_INTERNAL_NODE | RADIX_TREE_EXCEPTIONAL_ENTRY));
+       return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
 }
 
 /**