sysfs: use rb-tree for name lookups

sysfs: use rb-tree for name lookups

Use red-black tree for name lookups.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

fs/sysfs/dir.c

@@ -45,6 +45,9 @@ static void sysfs_link_sibling(struct sysfs_dirent *sd)
 	struct sysfs_dirent *parent_sd = sd->s_parent;
 	struct sysfs_dirent **pos;
 
+	struct rb_node **p;
+	struct rb_node *parent;
+
 	BUG_ON(sd->s_sibling);
 
 	if (sysfs_type(sd) == SYSFS_DIR)
@@ -60,6 +63,23 @@ static void sysfs_link_sibling(struct sysfs_dirent *sd)
 	}
 	sd->s_sibling = *pos;
 	*pos = sd;
+
+	p = &parent_sd->s_dir.name_tree.rb_node;
+	parent = NULL;
+	while (*p) {
+		int c;
+		parent = *p;
+#define node	rb_entry(parent, struct sysfs_dirent, name_node)
+		c = strcmp(sd->s_name, node->s_name);
+		if (c < 0) {
+			p = &node->name_node.rb_left;
+		} else {
+			p = &node->name_node.rb_right;
+		}
+#undef node
+	}
+	rb_link_node(&sd->name_node, parent, p);
+	rb_insert_color(&sd->name_node, &parent_sd->s_dir.name_tree);
 }
 
 /**
@@ -87,6 +107,8 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
 			break;
 		}
 	}
+
+	rb_erase(&sd->name_node, &sd->s_parent->s_dir.name_tree);
 }
 
 /**
@@ -546,15 +568,36 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
 				       const void *ns,
 				       const unsigned char *name)
 {
-	struct sysfs_dirent *sd;
+	struct rb_node *p = parent_sd->s_dir.name_tree.rb_node;
+	struct sysfs_dirent *found = NULL;
+
+	while (p) {
+		int c;
+#define node	rb_entry(p, struct sysfs_dirent, name_node)
+		c = strcmp(name, node->s_name);
+		if (c < 0) {
+			p = node->name_node.rb_left;
+		} else if (c > 0) {
+			p = node->name_node.rb_right;
+		} else {
+			found = node;
+			p = node->name_node.rb_left;
+		}
+#undef node
+	}
 
-	for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) {
-		if (ns && sd->s_ns && (sd->s_ns != ns))
-			continue;
-		if (!strcmp(sd->s_name, name))
-			return sd;
+	if (found && ns) {
+		while (found->s_ns && found->s_ns != ns) {
+			p = rb_next(&found->name_node);
+			if (!p)
+				return NULL;
+			found = rb_entry(p, struct sysfs_dirent, name_node);
+			if (strcmp(name, found->s_name))
+				return NULL;
+		}
 	}
-	return NULL;
+
+	return found;
 }
 
 /**

fs/sysfs/sysfs.h

@@ -11,6 +11,7 @@
 #include <linux/lockdep.h>
 #include <linux/kobject_ns.h>
 #include <linux/fs.h>
+#include <linux/rbtree.h>
 
 struct sysfs_open_dirent;
 
@@ -21,6 +22,8 @@ struct sysfs_elem_dir {
 	struct sysfs_dirent	*children;
 
 	unsigned long		subdirs;
+
+	struct rb_root		name_tree;
 };
 
 struct sysfs_elem_symlink {
@@ -61,6 +64,8 @@ struct sysfs_dirent {
 	struct sysfs_dirent	*s_sibling;
 	const char		*s_name;
 
+	struct rb_node		name_node;
+
 	const void		*s_ns; /* namespace tag */
 	union {
 		struct sysfs_elem_dir		s_dir;