sysfs: use rb-tree for inode number lookup

sysfs: use rb-tree for inode number lookup

This patch makes sysfs use red-black tree for inode number lookup.
Together with a previous patch to use red-black tree for name lookup,
this patch makes all sysfs lookups to have O(log n) complexity.

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

2 files changed, 52 insertions, 42 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a4846979d4e8..c3646d93a032 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -43,26 +43,30 @@ static DEFINE_IDA(sysfs_ino_ida);
 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)
                 parent_sd->s_dir.subdirs++;
 
-        /* Store directory entries in order by ino.  This allows
-         * readdir to properly restart without having to add a
-         * cursor into the s_dir.children list.
-         */
-        for (pos = &parent_sd->s_dir.children; *pos; pos = &(*pos)->s_sibling) {
-                if (sd->s_ino < (*pos)->s_ino)
-                        break;
+        p = &parent_sd->s_dir.inode_tree.rb_node;
+        parent = NULL;
+        while (*p) {
+                parent = *p;
+#define node    rb_entry(parent, struct sysfs_dirent, inode_node)
+                if (sd->s_ino < node->s_ino) {
+                        p = &node->inode_node.rb_left;
+                } else if (sd->s_ino > node->s_ino) {
+                        p = &node->inode_node.rb_right;
+                } else {
+                        printk(KERN_CRIT "sysfs: inserting duplicate inode '%lx'\n", sd->s_ino);
+                        BUG();
+                }
+#undef node
         }
-        sd->s_sibling = *pos;
-        *pos = sd;
+        rb_link_node(&sd->inode_node, parent, p);
+        rb_insert_color(&sd->inode_node, &parent_sd->s_dir.inode_tree);
 
         p = &parent_sd->s_dir.name_tree.rb_node;
         parent = NULL;
@@ -94,20 +98,10 @@ static void sysfs_link_sibling(struct sysfs_dirent *sd)
  */
 static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
 {
-        struct sysfs_dirent **pos;
-
         if (sysfs_type(sd) == SYSFS_DIR)
                 sd->s_parent->s_dir.subdirs--;
 
-        for (pos = &sd->s_parent->s_dir.children; *pos;
-             pos = &(*pos)->s_sibling) {
-                if (*pos == sd) {
-                        *pos = sd->s_sibling;
-                        sd->s_sibling = NULL;
-                        break;
-                }
-        }
-
+        rb_erase(&sd->inode_node, &sd->s_parent->s_dir.inode_tree);
         rb_erase(&sd->name_node, &sd->s_parent->s_dir.name_tree);
 }
 
@@ -788,21 +782,19 @@ void sysfs_remove_subdir(struct sysfs_dirent *sd)
 static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)
 {
         struct sysfs_addrm_cxt acxt;
-        struct sysfs_dirent **pos;
+        struct rb_node *pos;
 
         if (!dir_sd)
                 return;
 
         pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
         sysfs_addrm_start(&acxt, dir_sd);
-        pos = &dir_sd->s_dir.children;
-        while (*pos) {
-                struct sysfs_dirent *sd = *pos;
-
+        pos = rb_first(&dir_sd->s_dir.inode_tree);
+        while (pos) {
+                struct sysfs_dirent *sd = rb_entry(pos, struct sysfs_dirent, inode_node);
+                pos = rb_next(pos);
                 if (sysfs_type(sd) != SYSFS_DIR)
                         sysfs_remove_one(&acxt, sd);
-                else
-                        pos = &(*pos)->s_sibling;
         }
         sysfs_addrm_finish(&acxt);
 
@@ -925,12 +917,28 @@ static struct sysfs_dirent *sysfs_dir_pos(const void *ns,
                         pos = NULL;
         }
         if (!pos && (ino > 1) && (ino < INT_MAX)) {
-                pos = parent_sd->s_dir.children;
-                while (pos && (ino > pos->s_ino))
-                        pos = pos->s_sibling;
+                struct rb_node *p = parent_sd->s_dir.inode_tree.rb_node;
+                while (p) {
+#define node    rb_entry(p, struct sysfs_dirent, inode_node)
+                        if (ino < node->s_ino) {
+                                pos = node;
+                                p = node->inode_node.rb_left;
+                        } else if (ino > node->s_ino) {
+                                p = node->inode_node.rb_right;
+                        } else {
+                                pos = node;
+                                break;
+                        }
+#undef node
+                }
+        }
+        while (pos && pos->s_ns && pos->s_ns != ns) {
+                struct rb_node *p = rb_next(&pos->inode_node);
+                if (!p)
+                        pos = NULL;
+                else
+                        pos = rb_entry(p, struct sysfs_dirent, inode_node);
         }
-        while (pos && pos->s_ns && pos->s_ns != ns)
-                pos = pos->s_sibling;
         return pos;
 }
 
@@ -938,10 +946,13 @@ static struct sysfs_dirent *sysfs_dir_next_pos(const void *ns,
         struct sysfs_dirent *parent_sd, ino_t ino, struct sysfs_dirent *pos)
 {
         pos = sysfs_dir_pos(ns, parent_sd, ino, pos);
-        if (pos)
-                pos = pos->s_sibling;
-        while (pos && pos->s_ns && pos->s_ns != ns)
-                pos = pos->s_sibling;
+        if (pos) do {
+                struct rb_node *p = rb_next(&pos->inode_node);
+                if (!p)
+                        pos = NULL;
+                else
+                        pos = rb_entry(p, struct sysfs_dirent, inode_node);
+        } while (pos && pos->s_ns && pos->s_ns != ns);
         return pos;
 }
 
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 3c261681713b..ce29e28b766d 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -18,11 +18,10 @@ struct sysfs_open_dirent;
 /* type-specific structures for sysfs_dirent->s_* union members */
 struct sysfs_elem_dir {
         struct kobject          *kobj;
-        /* children list starts here and goes through sd->s_sibling */
-        struct sysfs_dirent     *children;
 
         unsigned long           subdirs;
 
+        struct rb_root          inode_tree;
         struct rb_root          name_tree;
 };
 
@@ -61,9 +60,9 @@ struct sysfs_dirent {
         struct lockdep_map      dep_map;
 #endif
         struct sysfs_dirent     *s_parent;
-        struct sysfs_dirent     *s_sibling;
         const char              *s_name;
 
+        struct rb_node          inode_node;
         struct rb_node          name_node;
 
         union {