kernfs: implement kernfs_syscall_ops->remount_fs() and ->show_options()

Add two super_block related syscall callbacks ->remount_fs() and
->show_options() to kernfs_syscall_ops.  These simply forward the
matching super_operations.

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

2 files changed, 26 insertions, 0 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 0d6ce895a9ee..70cc6983d9b5 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -19,10 +19,33 @@
 
 struct kmem_cache *kernfs_node_cache;
 
+static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
+{
+	struct kernfs_root *root = kernfs_info(sb)->root;
+	struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+	if (scops && scops->remount_fs)
+		return scops->remount_fs(root, flags, data);
+	return 0;
+}
+
+static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
+{
+	struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
+	struct kernfs_syscall_ops *scops = root->syscall_ops;
+
+	if (scops && scops->show_options)
+		return scops->show_options(sf, root);
+	return 0;
+}
+
 static const struct super_operations kernfs_sops = {
 	.statfs		= simple_statfs,
 	.drop_inode	= generic_delete_inode,
 	.evict_inode	= kernfs_evict_inode,
+
+	.remount_fs	= kernfs_sop_remount_fs,
+	.show_options	= kernfs_sop_show_options,
 };
 
 static int kernfs_fill_super(struct super_block *sb)
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5ddc47450335..5d5b7e947294 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -115,6 +115,9 @@ struct kernfs_node {
  * kernfs_node parameter.
  */
 struct kernfs_syscall_ops {
+	int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
+	int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
+
 	int (*mkdir)(struct kernfs_node *parent, const char *name,
 		     umode_t mode);
 	int (*rmdir)(struct kernfs_node *kn);