[PATCH v3 for-4.20 1/4] radix-tree: purge node allocation override hooks

[Jan Beulich <jbeulich@xxxxxxxx>]

These were needed by TMEM only, which is long gone. The Linux original
doesn't have such either. This effectively reverts one of the "Other
changes" from 8dc6738dbb3c ("Update radix-tree.[ch] from upstream Linux
to gain RCU awareness").

Positive side effect: Two cf_check go away.

While there also convert xmalloc()+memset() to xzalloc(). (Don't convert
to xvzalloc(), as that would require touching the freeing side, too.)

Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
v3: Add a missing blank line.
v2: New.

--- a/xen/common/radix-tree.c
+++ b/xen/common/radix-tree.c
@@ -53,12 +53,6 @@ struct rcu_node {
        struct rcu_head rcu_head;
 };
 
-static struct radix_tree_node *cf_check rcu_node_alloc(void *arg)
-{
-       struct rcu_node *rcu_node = xmalloc(struct rcu_node);
-       return rcu_node ? &rcu_node->node : NULL;
-}
-
 static void cf_check _rcu_node_free(struct rcu_head *head)
 {
        struct rcu_node *rcu_node =
@@ -66,26 +60,20 @@ static void cf_check _rcu_node_free(stru
        xfree(rcu_node);
 }
 
-static void cf_check rcu_node_free(struct radix_tree_node *node, void *arg)
-{
-       struct rcu_node *rcu_node = container_of(node, struct rcu_node, node);
-       call_rcu(&rcu_node->rcu_head, _rcu_node_free);
-}
-
 static struct radix_tree_node *radix_tree_node_alloc(
        struct radix_tree_root *root)
 {
-       struct radix_tree_node *ret;
-       ret = root->node_alloc(root->node_alloc_free_arg);
-       if (ret)
-               memset(ret, 0, sizeof(*ret));
-       return ret;
+       struct rcu_node *rcu_node = xzalloc(struct rcu_node);
+
+       return rcu_node ? &rcu_node->node : NULL;
 }
 
 static void radix_tree_node_free(
        struct radix_tree_root *root, struct radix_tree_node *node)
 {
-       root->node_free(node, root->node_alloc_free_arg);
+       struct rcu_node *rcu_node = container_of(node, struct rcu_node, node);
+
+       call_rcu(&rcu_node->rcu_head, _rcu_node_free);
 }
 
 /*
@@ -718,19 +706,6 @@ void radix_tree_destroy(
 void radix_tree_init(struct radix_tree_root *root)
 {
        memset(root, 0, sizeof(*root));
-       root->node_alloc = rcu_node_alloc;
-       root->node_free = rcu_node_free;
-}
-
-void radix_tree_set_alloc_callbacks(
-       struct radix_tree_root *root,
-       radix_tree_alloc_fn_t *node_alloc,
-       radix_tree_free_fn_t *node_free,
-       void *node_alloc_free_arg)
-{
-       root->node_alloc = node_alloc;
-       root->node_free = node_free;
-       root->node_alloc_free_arg = node_alloc_free_arg;
 }
 
 static __init unsigned long __maxindex(unsigned int height)
--- a/xen/include/xen/radix-tree.h
+++ b/xen/include/xen/radix-tree.h
@@ -66,11 +66,6 @@ typedef void radix_tree_free_fn_t(struct
 struct radix_tree_root {
        unsigned int            height;
        struct radix_tree_node  __rcu *rnode;
-
-       /* Allow to specify custom node alloc/dealloc routines. */
-       radix_tree_alloc_fn_t *node_alloc;
-       radix_tree_free_fn_t *node_free;
-       void *node_alloc_free_arg;
 };
 
 /*
@@ -78,11 +73,6 @@ struct radix_tree_root {
  */
 
 void radix_tree_init(struct radix_tree_root *root);
-void radix_tree_set_alloc_callbacks(
-       struct radix_tree_root *root,
-       radix_tree_alloc_fn_t *node_alloc,
-       radix_tree_free_fn_t *node_free,
-       void *node_alloc_free_arg);
 
 void radix_tree_destroy(
        struct radix_tree_root *root,