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-rw-r--r--include/linux/radix-tree.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 52b97db93830..af3581b8a451 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -461,6 +461,14 @@ static inline struct radix_tree_node *entry_to_node(void *ptr)
*
* This function updates @iter->index in the case of a successful lookup.
* For tagged lookup it also eats @iter->tags.
+ *
+ * There are several cases where 'slot' can be passed in as NULL to this
+ * function. These cases result from the use of radix_tree_iter_next() or
+ * radix_tree_iter_retry(). In these cases we don't end up dereferencing
+ * 'slot' because either:
+ * a) we are doing tagged iteration and iter->tags has been set to 0, or
+ * b) we are doing non-tagged iteration, and iter->index and iter->next_index
+ * have been set up so that radix_tree_chunk_size() returns 1 or 0.
*/
static __always_inline void **
radix_tree_next_slot(void **slot, struct radix_tree_iter *iter, unsigned flags)