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>

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index a484697..c3646d9 100644 (file)
--- 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 3c26168..ce29e28 100644 (file)
--- 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 {