From b3f9da79e7783ca4f1c1d4214af976c548629c1d Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Sat, 10 Aug 2024 23:14:44 -0400
Subject: [PATCH] lib/generic-radix-tree.c: add preallocation

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 include/linux/generic-radix-tree.h | 38 +++++++++++++++++++++++++-----
 lib/generic-radix-tree.c           | 16 ++++---------
 2 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/include/linux/generic-radix-tree.h b/include/linux/generic-radix-tree.h
index 8a3e1e886d1c..5b51c3d582d6 100644
--- a/include/linux/generic-radix-tree.h
+++ b/include/linux/generic-radix-tree.h
@@ -41,6 +41,7 @@
 #include <linux/limits.h>
 #include <linux/log2.h>
 #include <linux/math.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 
 struct genradix_root;
@@ -81,6 +82,10 @@ static inline struct genradix_node *genradix_root_to_node(struct genradix_root *
 	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
 }
 
+struct __genradix {
+	struct genradix_root		*root;
+};
+
 struct genradix_node {
 	union {
 		/* Interior node: */
@@ -91,9 +96,15 @@ struct genradix_node {
 	};
 };
 
-struct __genradix {
-	struct genradix_root		*root;
-};
+static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
+{
+	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
+}
+
+static inline void genradix_free_node(struct genradix_node *node)
+{
+	kfree(node);
+}
 
 /*
  * NOTE: currently, sizeof(_type) must not be larger than GENRADIX_NODE_SIZE:
@@ -209,7 +220,8 @@ void *__genradix_ptr(struct __genradix *, size_t);
 	 __genradix_ptr(&(_radix)->tree,			\
 			__genradix_idx_to_offset(_radix, _idx)))
 
-void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
+void *__genradix_ptr_alloc(struct __genradix *, size_t,
+			   struct genradix_node **, gfp_t);
 
 #define genradix_ptr_alloc_inlined(_radix, _idx, _gfp)			\
 	(__genradix_cast(_radix)					\
@@ -217,7 +229,15 @@ void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
 			__genradix_idx_to_offset(_radix, _idx)) ?:	\
 	  __genradix_ptr_alloc(&(_radix)->tree,				\
 			__genradix_idx_to_offset(_radix, _idx),		\
-			_gfp)))
+			NULL, _gfp)))
+
+#define genradix_ptr_alloc_preallocated_inlined(_radix, _idx, _new_node, _gfp)\
+	(__genradix_cast(_radix)					\
+	 (__genradix_ptr_inlined(&(_radix)->tree,			\
+			__genradix_idx_to_offset(_radix, _idx)) ?:	\
+	  __genradix_ptr_alloc(&(_radix)->tree,				\
+			__genradix_idx_to_offset(_radix, _idx),		\
+			_new_node, _gfp)))
 
 /**
  * genradix_ptr_alloc - get a pointer to a genradix entry, allocating it
@@ -232,7 +252,13 @@ void *__genradix_ptr_alloc(struct __genradix *, size_t, gfp_t);
 	(__genradix_cast(_radix)				\
 	 __genradix_ptr_alloc(&(_radix)->tree,			\
 			__genradix_idx_to_offset(_radix, _idx),	\
-			_gfp))
+			NULL, _gfp))
+
+#define genradix_ptr_alloc_preallocated(_radix, _idx, _new_node, _gfp)\
+	(__genradix_cast(_radix)				\
+	 __genradix_ptr_alloc(&(_radix)->tree,			\
+			__genradix_idx_to_offset(_radix, _idx),	\
+			_new_node, _gfp))
 
 struct genradix_iter {
 	size_t			offset;
diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index 4efae0663049..79e067b51488 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -15,27 +15,21 @@ void *__genradix_ptr(struct __genradix *radix, size_t offset)
 }
 EXPORT_SYMBOL(__genradix_ptr);
 
-static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
-{
-	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
-}
-
-static inline void genradix_free_node(struct genradix_node *node)
-{
-	kfree(node);
-}
-
 /*
  * Returns pointer to the specified byte @offset within @radix, allocating it if
  * necessary - newly allocated slots are always zeroed out:
  */
 void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
+			   struct genradix_node **preallocated,
 			   gfp_t gfp_mask)
 {
 	struct genradix_root *v = READ_ONCE(radix->root);
 	struct genradix_node *n, *new_node = NULL;
 	unsigned level;
 
+	if (preallocated)
+		swap(new_node, *preallocated);
+
 	/* Increase tree depth if necessary: */
 	while (1) {
 		struct genradix_root *r = v, *new_root;
@@ -219,7 +213,7 @@ int __genradix_prealloc(struct __genradix *radix, size_t size,
 	size_t offset;
 
 	for (offset = 0; offset < size; offset += GENRADIX_NODE_SIZE)
-		if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
+		if (!__genradix_ptr_alloc(radix, offset, NULL, gfp_mask))
 			return -ENOMEM;
 
 	return 0;