v4.19.13 snapshot.
diff --git a/net/ceph/string_table.c b/net/ceph/string_table.c
new file mode 100644
index 0000000..3191d9d
--- /dev/null
+++ b/net/ceph/string_table.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/slab.h>
+#include <linux/gfp.h>
+#include <linux/string.h>
+#include <linux/spinlock.h>
+#include <linux/ceph/string_table.h>
+
+static DEFINE_SPINLOCK(string_tree_lock);
+static struct rb_root string_tree = RB_ROOT;
+
+struct ceph_string *ceph_find_or_create_string(const char* str, size_t len)
+{
+ struct ceph_string *cs, *exist;
+ struct rb_node **p, *parent;
+ int ret;
+
+ exist = NULL;
+ spin_lock(&string_tree_lock);
+ p = &string_tree.rb_node;
+ while (*p) {
+ exist = rb_entry(*p, struct ceph_string, node);
+ ret = ceph_compare_string(exist, str, len);
+ if (ret > 0)
+ p = &(*p)->rb_left;
+ else if (ret < 0)
+ p = &(*p)->rb_right;
+ else
+ break;
+ exist = NULL;
+ }
+ if (exist && !kref_get_unless_zero(&exist->kref)) {
+ rb_erase(&exist->node, &string_tree);
+ RB_CLEAR_NODE(&exist->node);
+ exist = NULL;
+ }
+ spin_unlock(&string_tree_lock);
+ if (exist)
+ return exist;
+
+ cs = kmalloc(sizeof(*cs) + len + 1, GFP_NOFS);
+ if (!cs)
+ return NULL;
+
+ kref_init(&cs->kref);
+ cs->len = len;
+ memcpy(cs->str, str, len);
+ cs->str[len] = 0;
+
+retry:
+ exist = NULL;
+ parent = NULL;
+ p = &string_tree.rb_node;
+ spin_lock(&string_tree_lock);
+ while (*p) {
+ parent = *p;
+ exist = rb_entry(*p, struct ceph_string, node);
+ ret = ceph_compare_string(exist, str, len);
+ if (ret > 0)
+ p = &(*p)->rb_left;
+ else if (ret < 0)
+ p = &(*p)->rb_right;
+ else
+ break;
+ exist = NULL;
+ }
+ ret = 0;
+ if (!exist) {
+ rb_link_node(&cs->node, parent, p);
+ rb_insert_color(&cs->node, &string_tree);
+ } else if (!kref_get_unless_zero(&exist->kref)) {
+ rb_erase(&exist->node, &string_tree);
+ RB_CLEAR_NODE(&exist->node);
+ ret = -EAGAIN;
+ }
+ spin_unlock(&string_tree_lock);
+ if (ret == -EAGAIN)
+ goto retry;
+
+ if (exist) {
+ kfree(cs);
+ cs = exist;
+ }
+
+ return cs;
+}
+EXPORT_SYMBOL(ceph_find_or_create_string);
+
+void ceph_release_string(struct kref *ref)
+{
+ struct ceph_string *cs = container_of(ref, struct ceph_string, kref);
+
+ spin_lock(&string_tree_lock);
+ if (!RB_EMPTY_NODE(&cs->node)) {
+ rb_erase(&cs->node, &string_tree);
+ RB_CLEAR_NODE(&cs->node);
+ }
+ spin_unlock(&string_tree_lock);
+
+ kfree_rcu(cs, rcu);
+}
+EXPORT_SYMBOL(ceph_release_string);
+
+bool ceph_strings_empty(void)
+{
+ return RB_EMPTY_ROOT(&string_tree);
+}