mm: bdi: expose the BDI object in sysfs for NFS

Register NFS' backing_dev_info under sysfs with the name "nfs-MAJOR:MINOR"

Signed-off-by: Miklos Szeredi <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Trond Myklebust <[e-mail]>
Cc: "J. Bruce Fields" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/nfs/super.c

···
 	return nfs_compare_mount_options(sb, server, mntflags);
 }
 
+static int nfs_bdi_register(struct nfs_server *server)
+{
+	return bdi_register_dev(&server->backing_dev_info, server->s_dev);
+}
+
 static int nfs_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *raw_data, struct vfsmount *mnt)
 {
···
 	if (s->s_fs_info != server) {
 		nfs_free_server(server);
 		server = NULL;
+	} else {
+		error = nfs_bdi_register(server);
+		if (error)
+			goto error_splat_super;
 	}
 
 	if (!s->s_root) {
···
 {
 	struct nfs_server *server = NFS_SB(s);
 
+	bdi_unregister(&server->backing_dev_info);
 	kill_anon_super(s);
 	nfs_free_server(server);
 }
···
 	if (s->s_fs_info != server) {
 		nfs_free_server(server);
 		server = NULL;
+	} else {
+		error = nfs_bdi_register(server);
+		if (error)
+			goto error_splat_super;
 	}
 
 	if (!s->s_root) {
···
 	if (s->s_fs_info != server) {
 		nfs_free_server(server);
 		server = NULL;
+	} else {
+		error = nfs_bdi_register(server);
+		if (error)
+			goto error_splat_super;
 	}
 
 	if (!s->s_root) {
···
 	if (s->s_fs_info != server) {
 		nfs_free_server(server);
 		server = NULL;
+	} else {
+		error = nfs_bdi_register(server);
+		if (error)
+			goto error_splat_super;
 	}
 
 	if (!s->s_root) {
···
 	if (s->s_fs_info != server) {
 		nfs_free_server(server);
 		server = NULL;
+	} else {
+		error = nfs_bdi_register(server);
+		if (error)
+			goto error_splat_super;
 	}
 
 	if (!s->s_root) {