sysfs, kernfs: introduce sysfs_root_sd

Currently, it's assumed that there's a single kernfs hierarchy in the
system anchored at sysfs_root which is defined as a global struct.  To
allow other users of kernfs, this will be made dynamic.  Introduce a
new global variable sysfs_root_sd which points to &sysfs_root and
convert all &sysfs_root users.

This patch doesn't introduce any behavior difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/sysfs/dir.c

@@ -68,7 +68,7 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
 	if (kobj->parent)
 		parent_sd = kobj->parent->sd;
 	else
-		parent_sd = &sysfs_root;
+		parent_sd = sysfs_root_sd;
 
 	if (!parent_sd)
 		return -ENOENT;
@@ -134,7 +134,7 @@ int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 
 	BUG_ON(!sd->s_parent);
 	new_parent_sd = new_parent_kobj && new_parent_kobj->sd ?
-		new_parent_kobj->sd : &sysfs_root;
+		new_parent_kobj->sd : sysfs_root_sd;
 
 	return kernfs_rename_ns(sd, new_parent_sd, sd->s_name, new_ns);
 }

fs/sysfs/mount.c

@@ -32,7 +32,7 @@ static const struct super_operations sysfs_ops = {
 	.evict_inode	= sysfs_evict_inode,
 };
 
-struct sysfs_dirent sysfs_root = {
+static struct sysfs_dirent sysfs_root = {
 	.s_name		= "",
 	.s_count	= ATOMIC_INIT(1),
 	.s_flags	= SYSFS_DIR,
@@ -40,6 +40,8 @@ struct sysfs_dirent sysfs_root = {
 	.s_ino		= 1,
 };
 
+struct sysfs_dirent *sysfs_root_sd = &sysfs_root;
+
 static int sysfs_fill_super(struct super_block *sb)
 {
 	struct inode *inode;
@@ -53,7 +55,7 @@ static int sysfs_fill_super(struct super_block *sb)
 
 	/* get root inode, initialize and unlock it */
 	mutex_lock(&sysfs_mutex);
-	inode = sysfs_get_inode(sb, &sysfs_root);
+	inode = sysfs_get_inode(sb, sysfs_root_sd);
 	mutex_unlock(&sysfs_mutex);
 	if (!inode) {
 		pr_debug("sysfs: could not get root inode\n");
@@ -66,7 +68,7 @@ static int sysfs_fill_super(struct super_block *sb)
 		pr_debug("%s: could not get root dentry!\n", __func__);
 		return -ENOMEM;
 	}
-	root->d_fsdata = &sysfs_root;
+	root->d_fsdata = sysfs_root_sd;
 	sb->s_root = root;
 	sb->s_d_op = &sysfs_dentry_ops;
 	return 0;

fs/sysfs/symlink.c

@@ -70,7 +70,7 @@ static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
 	struct sysfs_dirent *parent_sd = NULL;
 
 	if (!kobj)
-		parent_sd = &sysfs_root;
+		parent_sd = sysfs_root_sd;
 	else
 		parent_sd = kobj->sd;
 
@@ -144,7 +144,7 @@ void sysfs_remove_link(struct kobject *kobj, const char *name)
 	struct sysfs_dirent *parent_sd = NULL;
 
 	if (!kobj)
-		parent_sd = &sysfs_root;
+		parent_sd = sysfs_root_sd;
 	else
 		parent_sd = kobj->sd;
 
@@ -170,7 +170,7 @@ int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
 	int result;
 
 	if (!kobj)
-		parent_sd = &sysfs_root;
+		parent_sd = sysfs_root_sd;
 	else
 		parent_sd = kobj->sd;
 

fs/sysfs/sysfs.h

@@ -28,7 +28,7 @@ struct sysfs_super_info {
 	const void		*ns;
 };
 #define sysfs_info(SB) ((struct sysfs_super_info *)(SB->s_fs_info))
-extern struct sysfs_dirent sysfs_root;
+extern struct sysfs_dirent *sysfs_root_sd;
 extern struct kmem_cache *sysfs_dir_cachep;
 
 /*