#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_indirect_ptr(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 ***/
*/
static inline int radix_tree_deref_retry(void *arg)
{
- return unlikely(radix_tree_is_indirect_ptr(arg));
+ return unlikely(radix_tree_is_internal_node(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);
}
/**
*/
static inline void radix_tree_replace_slot(void **pslot, void *item)
{
- BUG_ON(radix_tree_is_indirect_ptr(item));
+ BUG_ON(radix_tree_is_internal_node(item));
rcu_assign_pointer(*pslot, item);
}
struct radix_tree_node *node);
void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_delete(struct radix_tree_root *, unsigned long);
-unsigned int
-radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
- unsigned long first_index, unsigned int max_items);
+struct radix_tree_node *radix_tree_replace_clear_tags(
+ struct radix_tree_root *root,
+ unsigned long index, void *entry);
+unsigned int radix_tree_gang_lookup(struct radix_tree_root *root,
+ void **results, unsigned long first_index,
+ unsigned int max_items);
unsigned int radix_tree_gang_lookup_slot(struct radix_tree_root *root,
void ***results, unsigned long *indices,
unsigned long first_index, unsigned int max_items);
if (unlikely(!iter->tags))
return NULL;
while (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
- radix_tree_is_indirect_ptr(slot[1])) {
+ radix_tree_is_internal_node(slot[1])) {
if (entry_to_node(slot[1]) == canon) {
iter->tags >>= 1;
iter->index = __radix_tree_iter_add(iter, 1);
iter->index = __radix_tree_iter_add(iter, 1);
if (IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
- radix_tree_is_indirect_ptr(*slot)) {
+ radix_tree_is_internal_node(*slot)) {
if (entry_to_node(*slot) == canon)
continue;
iter->next_index = iter->index;