sysfs, kernfs: implement kernfs_create/destroy_root()
There currently is single kernfs hierarchy in the whole system which
is used for sysfs. kernfs needs to support multiple hierarchies to
allow other users. This patch introduces struct kernfs_root which
serves as the root of each kernfs hierarchy and implements
kernfs_create/destroy_root().
* Each kernfs_root is associated with a root sd (sysfs_dentry). The
root is freed when the root sd is released and kernfs_destory_root()
simply invokes kernfs_remove() on the root sd. sysfs_remove_one()
is updated to handle release of the root sd. Note that ps_iattr
update in sysfs_remove_one() is trivially updated for readability.
* Root sd's are now dynamically allocated using sysfs_new_dirent().
Update sysfs_alloc_ino() so that it gives out ino from 1 so that the
root sd still gets ino 1.
* While kernfs currently only points to the root sd, it'll soon grow
fields which are specific to each hierarchy. As determining a given
sd's root will be necessary, sd->s_dir.root is added. This backlink
fits better as a separate field in sd; however, sd->s_dir is inside
union with space to spare, so use it to save space and provide
kernfs_root() accessor to determine the root sd.
* As hierarchies may be destroyed now, each mount needs to hold onto
the hierarchy it's attached to. Update sysfs_fill_super() and
sysfs_kill_sb() so that they get and put the kernfs_root
respectively.
* sysfs_root is replaced with kernfs_root which is dynamically created
by invoking kernfs_create_root() from sysfs_init().
This patch doesn't introduce any visible behavior changes.
v2: kernfs_create_root() forgot to set @sd->priv. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 7cbd1fc..0b5661b 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -32,15 +32,8 @@
.evict_inode = sysfs_evict_inode,
};
-static struct sysfs_dirent sysfs_root = {
- .s_name = "",
- .s_count = ATOMIC_INIT(1),
- .s_flags = SYSFS_DIR,
- .s_mode = S_IFDIR | S_IRUGO | S_IXUGO,
- .s_ino = 1,
-};
-
-struct sysfs_dirent *sysfs_root_sd = &sysfs_root;
+static struct kernfs_root *sysfs_root;
+struct sysfs_dirent *sysfs_root_sd;
static int sysfs_fill_super(struct super_block *sb)
{
@@ -68,6 +61,7 @@
pr_debug("%s: could not get root dentry!\n", __func__);
return -ENOMEM;
}
+ kernfs_get(sysfs_root_sd);
root->d_fsdata = sysfs_root_sd;
sb->s_root = root;
sb->s_d_op = &sysfs_dentry_ops;
@@ -138,11 +132,15 @@
static void sysfs_kill_sb(struct super_block *sb)
{
struct sysfs_super_info *info = sysfs_info(sb);
- /* Remove the superblock from fs_supers/s_instances
+ struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
+
+ /*
+ * Remove the superblock from fs_supers/s_instances
* so we can't find it, before freeing sysfs_super_info.
*/
kill_anon_super(sb);
free_sysfs_super_info(info);
+ kernfs_put(root_sd);
}
static struct file_system_type sysfs_fs_type = {
@@ -166,12 +164,21 @@
if (err)
goto out_err;
+ sysfs_root = kernfs_create_root(NULL);
+ if (IS_ERR(sysfs_root)) {
+ err = PTR_ERR(sysfs_root);
+ goto out_err;
+ }
+ sysfs_root_sd = sysfs_root->sd;
+
err = register_filesystem(&sysfs_fs_type);
if (err)
- goto out_err;
+ goto out_destroy_root;
return 0;
+out_destroy_root:
+ kernfs_destroy_root(sysfs_root);
out_err:
kmem_cache_destroy(sysfs_dir_cachep);
sysfs_dir_cachep = NULL;