Subject: [RFC PATCH 05/20] kho: add data argument to radix walk callback

From: Jork Loeser <[email-masked]>
Date: Wed, 27 May 2026 17:41:47 -0700

From: "Pratyush Yadav (Google)" <[email-masked]>

Add an opaque data pointer argument to kho_radix_walk_cb_t. This can be
used for callers to pass extra information to the callback.

Signed-off-by: Pratyush Yadav (Google) <[email-masked]>
Signed-off-by: Jork Loeser <[email-masked]>
---
 include/linux/kho_radix_tree.h     |  8 ++++----
 kernel/liveupdate/kexec_handover.c | 24 +++++++++++++-----------
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/include/linux/kho_radix_tree.h b/include/linux/kho_radix_tree.h
index fe7151d89361..6c0f7d82716b 100644
--- a/include/linux/kho_radix_tree.h
+++ b/include/linux/kho_radix_tree.h
@@ -44,8 +44,8 @@ struct kho_radix_tree {
  * return value is directly returned to the caller.
  */
 struct kho_radix_walk_cb {
-	int (*key)(unsigned long key);
-	int (*table)(phys_addr_t phys);
+	int (*key)(unsigned long key, void *data);
+	int (*table)(phys_addr_t phys, void *data);
 };
 
 #ifdef CONFIG_KEXEC_HANDOVER
@@ -53,7 +53,7 @@ struct kho_radix_walk_cb {
 int kho_radix_add_key(struct kho_radix_tree *tree, unsigned long key);
 void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key);
 int kho_radix_walk_tree(struct kho_radix_tree *tree,
-			const struct kho_radix_walk_cb *cb);
+			const struct kho_radix_walk_cb *cb, void *data);
 
 #else  /* #ifdef CONFIG_KEXEC_HANDOVER */
 
@@ -66,7 +66,7 @@ static inline void kho_radix_del_key(struct kho_radix_tree *tree,
 				     unsigned long key) { }
 
 static inline int kho_radix_walk_tree(struct kho_radix_tree *tree,
-				      const struct kho_radix_walk_cb *cb)
+				      const struct kho_radix_walk_cb *cb, void *data)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 0f8d058f1a27..f6de6bf63226 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -267,14 +267,14 @@ void kho_radix_del_key(struct kho_radix_tree *tree, unsigned long key)
 EXPORT_SYMBOL_GPL(kho_radix_del_key);
 
 static int kho_radix_walk_leaf(struct kho_radix_leaf *leaf, unsigned long key,
-			       const struct kho_radix_walk_cb *cb)
+			       const struct kho_radix_walk_cb *cb, void *data)
 {
 	unsigned long *bitmap = (unsigned long *)leaf;
 	unsigned int i;
 	int err;
 
 	if (cb->table) {
-		err = cb->table(virt_to_phys(leaf));
+		err = cb->table(virt_to_phys(leaf), data);
 		if (err)
 			return err;
 	}
@@ -283,7 +283,7 @@ static int kho_radix_walk_leaf(struct kho_radix_leaf *leaf, unsigned long key,
 		return 0;
 
 	for_each_set_bit(i, bitmap, PAGE_SIZE * BITS_PER_BYTE) {
-		err = cb->key(key | i);
+		err = cb->key(key | i, data);
 		if (err)
 			return err;
 	}
@@ -293,7 +293,7 @@ static int kho_radix_walk_leaf(struct kho_radix_leaf *leaf, unsigned long key,
 
 static int __kho_radix_walk_tree(struct kho_radix_node *root,
 				 unsigned int level, unsigned long start,
-				 const struct kho_radix_walk_cb *cb)
+				 const struct kho_radix_walk_cb *cb, void *data)
 {
 	struct kho_radix_node *node;
 	struct kho_radix_leaf *leaf;
@@ -302,7 +302,7 @@ static int __kho_radix_walk_tree(struct kho_radix_node *root,
 	int err;
 
 	if (cb->table) {
-		err = cb->table(virt_to_phys(root));
+		err = cb->table(virt_to_phys(root), data);
 		if (err)
 			return err;
 	}
@@ -323,10 +323,10 @@ static int __kho_radix_walk_tree(struct kho_radix_node *root,
 			 * node is pointing to the level 0 bitmap.
 			 */
 			leaf = (struct kho_radix_leaf *)node;
-			err = kho_radix_walk_leaf(leaf, key, cb);
+			err = kho_radix_walk_leaf(leaf, key, cb, data);
 		} else {
 			err  = __kho_radix_walk_tree(node, level - 1,
-						     key, cb);
+						     key, cb, data);
 		}
 
 		if (err)
@@ -340,6 +340,7 @@ static int __kho_radix_walk_tree(struct kho_radix_node *root,
  * kho_radix_walk_tree - Traverses the radix tree and calls a callback for each key.
  * @tree: A pointer to the KHO radix tree to walk.
  * @cb:   Set of callbacks to be invoked during the tree walk.
+ * @data: Opaque data pointer passed to each callback in @cb.
  *
  * This function walks the radix tree, searching from the top level down to the
  * lowest level (level 0), invoking the appropriate callbacks.
@@ -348,14 +349,15 @@ static int __kho_radix_walk_tree(struct kho_radix_node *root,
  *         value from the callback that stopped the walk.
  */
 int kho_radix_walk_tree(struct kho_radix_tree *tree,
-			const struct kho_radix_walk_cb *cb)
+			const struct kho_radix_walk_cb *cb, void *data)
 {
 	if (WARN_ON_ONCE(!tree->root))
 		return -EINVAL;
 
 	guard(mutex)(&tree->lock);
 
-	return __kho_radix_walk_tree(tree->root, KHO_TREE_MAX_DEPTH - 1, 0, cb);
+	return __kho_radix_walk_tree(tree->root, KHO_TREE_MAX_DEPTH - 1, 0, cb,
+				     data);
 }
 EXPORT_SYMBOL_GPL(kho_radix_walk_tree);
 
@@ -486,7 +488,7 @@ static struct page *__init kho_get_preserved_page(phys_addr_t phys,
 	return pfn_to_page(pfn);
 }
 
-static int __init kho_preserved_memory_reserve(unsigned long key)
+static int __init kho_preserved_memory_reserve(unsigned long key, void *data)
 {
 	union kho_page_info info;
 	struct page *page;
@@ -1414,7 +1416,7 @@ static int __init kho_mem_retrieve(const void *fdt)
 
 	kho_in.radix_tree.root = phys_to_virt(kho_get_mem_map_phys(fdt));
 	mutex_init(&kho_in.radix_tree.lock);
-	return kho_radix_walk_tree(&kho_in.radix_tree, &cb);
+	return kho_radix_walk_tree(&kho_in.radix_tree, &cb, NULL);
 }
 
 static __init int kho_out_fdt_setup(void)
-- 
2.43.0