From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Subject: radix-tree: add missing sibling entry functionality
The code I previously added to enable multiorder radix tree entries was
untested and therefore buggy. This commit adds the support functions that
Ross and I decided were necessary over a four-week period of iterating
various designs.
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Cc: Kirill Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/radix-tree.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff -puN lib/radix-tree.c~radix-tree-add-missing-sibling-entry-functionality lib/radix-tree.c
--- a/lib/radix-tree.c~radix-tree-add-missing-sibling-entry-functionality
+++ a/lib/radix-tree.c
@@ -80,6 +80,46 @@ static inline void *indirect_to_ptr(void
return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
}
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+/* Sibling slots point directly to another slot in the same node */
+static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
+{
+ void **ptr = node;
+ return (parent->slots <= ptr) &&
+ (ptr < parent->slots + RADIX_TREE_MAP_SIZE);
+}
+#else
+static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
+{
+ return false;
+}
+#endif
+
+static inline unsigned long get_slot_offset(struct radix_tree_node *parent,
+ void **slot)
+{
+ return slot - parent->slots;
+}
+
+static unsigned radix_tree_descend(struct radix_tree_node *parent,
+ struct radix_tree_node **nodep, unsigned offset)
+{
+ void **entry = rcu_dereference_raw(parent->slots[offset]);
+
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+ if (radix_tree_is_indirect_ptr(entry)) {
+ unsigned long siboff = get_slot_offset(parent, entry);
+ if (siboff < RADIX_TREE_MAP_SIZE) {
+ offset = siboff;
+ entry = rcu_dereference_raw(parent->slots[offset]);
+ }
+ }
+#endif
+
+ *nodep = (void *)entry;
+ return offset;
+}
+
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
_
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