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>

4 files changed, 11 insertions, 9 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index e5c4e7118050..2fea501889e7 100644
--- a/fs/sysfs/dir.c
+++ b/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);
 }
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 0c80f0379016..7cbd1fce2826 100644
--- a/fs/sysfs/mount.c
+++ b/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;
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 6797c9c2e43a..62f0e014ec48 100644
--- a/fs/sysfs/symlink.c
+++ b/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;
 
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index ce97907e2894..2b217cef90be 100644
--- a/fs/sysfs/sysfs.h
+++ b/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;
 
 /*