radix-tree: Fix __rcu annotations

Many places were missing __rcu annotations.  A few places needed a few
lines of explanation about why it was safe to not use RCU accessors.
Add a custom CFLAGS setting to the Makefile to ensure that new patches
don't miss RCU annotations.

Signed-off-by: Matthew Wilcox <[email protected]>

Author: Matthew Wilcox

include/linux/radix-tree.h

@@ -221,37 +221,36 @@ static inline unsigned int iter_shift(const struct radix_tree_iter *iter)
  */
 
 /**
- * radix_tree_deref_slot	- dereference a slot
- * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
- * Returns:	item that was stored in that slot with any direct pointer flag
- *		removed.
+ * radix_tree_deref_slot - dereference a slot
+ * @slot: slot pointer, returned by radix_tree_lookup_slot
  *
  * For use with radix_tree_lookup_slot().  Caller must hold tree at least read
  * 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.
+ *
+ * Return: entry stored in that slot.
  */
-static inline void *radix_tree_deref_slot(void **pslot)
+static inline void *radix_tree_deref_slot(void __rcu **slot)
 {
-	return rcu_dereference(*pslot);
+	return rcu_dereference(*slot);
 }
 
 /**
- * radix_tree_deref_slot_protected	- dereference a slot without RCU lock but with tree lock held
- * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
- * Returns:	item that was stored in that slot with any direct pointer flag
- *		removed.
- *
- * Similar to radix_tree_deref_slot but only used during migration when a pages
- * mapping is being moved. The caller does not hold the RCU read lock but it
- * must hold the tree lock to prevent parallel updates.
+ * radix_tree_deref_slot_protected - dereference a slot with tree lock held
+ * @slot: slot pointer, returned by radix_tree_lookup_slot
+ *
+ * Similar to radix_tree_deref_slot.  The caller does not hold the RCU read
+ * lock but it must hold the tree lock to prevent parallel updates.
+ *
+ * Return: entry stored in that slot.
  */
-static inline void *radix_tree_deref_slot_protected(void **pslot,
+static inline void *radix_tree_deref_slot_protected(void __rcu **slot,
 							spinlock_t *treelock)
 {
-	return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
+	return rcu_dereference_protected(*slot, lockdep_is_held(treelock));
 }
 
 /**
@@ -287,9 +286,9 @@ static inline int radix_tree_exception(void *arg)
 	return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
 }
 
-int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
+int __radix_tree_create(struct radix_tree_root *, unsigned long index,
 			unsigned order, struct radix_tree_node **nodep,
-			void ***slotp);
+			void __rcu ***slotp);
 int __radix_tree_insert(struct radix_tree_root *, unsigned long index,
 			unsigned order, void *);
 static inline int radix_tree_insert(struct radix_tree_root *root,
@@ -298,58 +297,55 @@ static inline int radix_tree_insert(struct radix_tree_root *root,
 	return __radix_tree_insert(root, index, 0, entry);
 }
 void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
-			  struct radix_tree_node **nodep, void ***slotp);
+			  struct radix_tree_node **nodep, void __rcu ***slotp);
 void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
-void **radix_tree_lookup_slot(const struct radix_tree_root *, unsigned long);
+void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
+					unsigned long index);
 typedef void (*radix_tree_update_node_t)(struct radix_tree_node *, void *);
-void __radix_tree_replace(struct radix_tree_root *root,
-			  struct radix_tree_node *node,
-			  void **slot, void *item,
+void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
+			  void __rcu **slot, void *entry,
 			  radix_tree_update_node_t update_node, void *private);
 void radix_tree_iter_replace(struct radix_tree_root *,
-		const struct radix_tree_iter *, void **slot, void *item);
-void radix_tree_replace_slot(struct radix_tree_root *root,
-			     void **slot, void *item);
-void __radix_tree_delete_node(struct radix_tree_root *root,
-			      struct radix_tree_node *node,
+		const struct radix_tree_iter *, void __rcu **slot, void *entry);
+void radix_tree_replace_slot(struct radix_tree_root *,
+			     void __rcu **slot, void *entry);
+void __radix_tree_delete_node(struct radix_tree_root *,
+			      struct radix_tree_node *,
 			      radix_tree_update_node_t update_node,
 			      void *private);
 void radix_tree_iter_delete(struct radix_tree_root *,
-				struct radix_tree_iter *iter, void **slot);
+			struct radix_tree_iter *iter, void __rcu **slot);
 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
-void radix_tree_clear_tags(struct radix_tree_root *root,
-			   struct radix_tree_node *node,
-			   void **slot);
+void radix_tree_clear_tags(struct radix_tree_root *, struct radix_tree_node *,
+			   void __rcu **slot);
 unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
 			void **results, unsigned long first_index,
 			unsigned int max_items);
 unsigned int radix_tree_gang_lookup_slot(const struct radix_tree_root *,
-			void ***results, unsigned long *indices,
+			void __rcu ***results, unsigned long *indices,
 			unsigned long first_index, unsigned int max_items);
 int radix_tree_preload(gfp_t gfp_mask);
 int radix_tree_maybe_preload(gfp_t gfp_mask);
 int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order);
 void radix_tree_init(void);
-void *radix_tree_tag_set(struct radix_tree_root *root,
+void *radix_tree_tag_set(struct radix_tree_root *,
 			unsigned long index, unsigned int tag);
-void *radix_tree_tag_clear(struct radix_tree_root *root,
+void *radix_tree_tag_clear(struct radix_tree_root *,
 			unsigned long index, unsigned int tag);
 int radix_tree_tag_get(const struct radix_tree_root *,
 			unsigned long index, unsigned int tag);
 void radix_tree_iter_tag_set(struct radix_tree_root *,
 		const struct radix_tree_iter *iter, unsigned int tag);
 void radix_tree_iter_tag_clear(struct radix_tree_root *,
 		const struct radix_tree_iter *iter, unsigned int tag);
-unsigned int
-radix_tree_gang_lookup_tag(const struct radix_tree_root *, void **results,
-		unsigned long first_index, unsigned int max_items,
-		unsigned int tag);
-unsigned int
-radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *, void ***results,
-		unsigned long first_index, unsigned int max_items,
-		unsigned int tag);
-int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag);
+unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
+		void **results, unsigned long first_index,
+		unsigned int max_items, unsigned int tag);
+unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
+		void __rcu ***results, unsigned long first_index,
+		unsigned int max_items, unsigned int tag);
+int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
 
 static inline void radix_tree_preload_end(void)
 {
@@ -361,7 +357,7 @@ int radix_tree_split(struct radix_tree_root *, unsigned long index,
 			unsigned new_order);
 int radix_tree_join(struct radix_tree_root *, unsigned long index,
 			unsigned new_order, void *);
-void **idr_get_free(struct radix_tree_root *, struct radix_tree_iter *,
+void __rcu **idr_get_free(struct radix_tree_root *, struct radix_tree_iter *,
 			gfp_t, int end);
 
 enum {
@@ -377,7 +373,7 @@ enum {
  * @start:	iteration starting index
  * Returns:	NULL
  */
-static __always_inline void **
+static __always_inline void __rcu **
 radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
 {
 	/*
@@ -406,7 +402,7 @@ radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
  * Also it fills @iter with data about chunk: position in the tree (index),
  * its end (next_index), and constructs a bit mask for tagged iterating (tags).
  */
-void **radix_tree_next_chunk(const struct radix_tree_root *,
+void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,
 			     struct radix_tree_iter *iter, unsigned flags);
 
 /**
@@ -419,7 +415,8 @@ void **radix_tree_next_chunk(const struct radix_tree_root *,
  * containing it and updates @iter to describe the entry.  If @index is not
  * present, it returns NULL.
  */
-static inline void **radix_tree_iter_lookup(const struct radix_tree_root *root,
+static inline void __rcu **
+radix_tree_iter_lookup(const struct radix_tree_root *root,
 			struct radix_tree_iter *iter, unsigned long index)
 {
 	radix_tree_iter_init(iter, index);
@@ -436,7 +433,8 @@ static inline void **radix_tree_iter_lookup(const struct radix_tree_root *root,
  * which is at least @index.  If @index is larger than any present entry, this
  * function returns NULL.  The @iter is updated to describe the entry found.
  */
-static inline void **radix_tree_iter_find(const struct radix_tree_root *root,
+static inline void __rcu **
+radix_tree_iter_find(const struct radix_tree_root *root,
 			struct radix_tree_iter *iter, unsigned long index)
 {
 	radix_tree_iter_init(iter, index);
@@ -453,7 +451,7 @@ static inline void **radix_tree_iter_find(const struct radix_tree_root *root,
  * and continue the iteration.
  */
 static inline __must_check
-void **radix_tree_iter_retry(struct radix_tree_iter *iter)
+void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)
 {
 	iter->next_index = iter->index;
 	iter->tags = 0;
@@ -476,7 +474,7 @@ __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
  * have been invalidated by an insertion or deletion.  Call this function
  * before releasing the lock to continue the iteration from the next index.
  */
-void **__must_check radix_tree_iter_resume(void **slot,
+void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,
 					struct radix_tree_iter *iter);
 
 /**
@@ -492,11 +490,11 @@ radix_tree_chunk_size(struct radix_tree_iter *iter)
 }
 
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
-void ** __radix_tree_next_slot(void **slot, struct radix_tree_iter *iter,
-				unsigned flags);
+void __rcu **__radix_tree_next_slot(void __rcu **slot,
+				struct radix_tree_iter *iter, unsigned flags);
 #else
 /* Can't happen without sibling entries, but the compiler can't tell that */
-static inline void ** __radix_tree_next_slot(void **slot,
+static inline void __rcu **__radix_tree_next_slot(void __rcu **slot,
 				struct radix_tree_iter *iter, unsigned flags)
 {
 	return slot;
@@ -522,8 +520,8 @@ static inline void ** __radix_tree_next_slot(void **slot,
  * 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)
+static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
+				struct radix_tree_iter *iter, unsigned flags)
 {
 	if (flags & RADIX_TREE_ITER_TAGGED) {
 		iter->tags >>= 1;

lib/Makefile

@@ -24,6 +24,8 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
 	 earlycpio.o seq_buf.o nmi_backtrace.o nodemask.o win_minmax.o
 
+CFLAGS_radix-tree.o += -DCONFIG_SPARSE_RCU_POINTER
+
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 lib-$(CONFIG_HAS_DMA) += dma-noop.o