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>

---
 fs/sysfs/dir.c   |   89 ++++++++++++++++++++++++++++++-------------------------
 fs/sysfs/sysfs.h |    5 +--
 2 files changed, 52 insertions(+), 42 deletions(-)

Index: linux-3.0-rc7-fast/fs/sysfs/dir.c
===================================================================
--- linux-3.0-rc7-fast.orig/fs/sysfs/dir.c	2011-07-20 20:55:15.000000000 +0200
+++ linux-3.0-rc7-fast/fs/sysfs/dir.c	2011-07-20 23:30:47.000000000 +0200
@@ -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;
@@ -97,20 +101,10 @@ static void sysfs_link_sibling(struct sy
  */
 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);
 }
 
@@ -778,21 +772,19 @@ void sysfs_remove_subdir(struct sysfs_di
 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);
 
@@ -915,12 +907,28 @@ static struct sysfs_dirent *sysfs_dir_po
 			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 (node->s_ino > 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;
 }
 
@@ -928,10 +936,13 @@ static struct sysfs_dirent *sysfs_dir_ne
 	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;
 }
 
Index: linux-3.0-rc7-fast/fs/sysfs/sysfs.h
===================================================================
--- linux-3.0-rc7-fast.orig/fs/sysfs/sysfs.h	2011-07-20 20:46:50.000000000 +0200
+++ linux-3.0-rc7-fast/fs/sysfs/sysfs.h	2011-07-20 21:00:28.000000000 +0200
@@ -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 {