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>

2 files changed, 55 insertions, 7 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 7d240e6b7176..3e937da224d4 100644
--- a/fs/sysfs/dir.c
+++ b/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;
 }
 
 /**
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 6348e2c753f6..fe1a9e8650bf 100644
--- a/fs/sysfs/sysfs.h
+++ b/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;