mount_pseudo(): drop 'name' argument, switch to d_make_root()

Once upon a time we used to set ->d_name of e.g. pipefs root
so that d_path() on pipes would work.  These days it's
completely pointless - dentries of pipes are not even connected
to pipefs root.  However, mount_pseudo() had set the root
dentry name (passed as the second argument) and callers
kept inventing names to pass to it.  Including those that
didn't *have* any non-root dentries to start with...

All of that had been pointless for about 8 years now; it's
time to get rid of that cargo-culting...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/ia64/kernel/perfmon.c

@@ -602,7 +602,7 @@ static const struct dentry_operations pfmfs_dentry_operations;
 static struct dentry *
 pfmfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "pfm:", NULL, &pfmfs_dentry_operations,
+	return mount_pseudo(fs_type, NULL, &pfmfs_dentry_operations,
 			PFMFS_MAGIC);
 }
 

drivers/dax/super.c

@@ -440,7 +440,7 @@ static const struct super_operations dax_sops = {
 static struct dentry *dax_mount(struct file_system_type *fs_type,
 		int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "dax:", &dax_sops, NULL, DAXFS_MAGIC);
+	return mount_pseudo(fs_type, &dax_sops, NULL, DAXFS_MAGIC);
 }
 
 static struct file_system_type dax_fs_type = {

drivers/gpu/drm/drm_drv.c

@@ -535,11 +535,7 @@ static struct vfsmount *drm_fs_mnt;
 static struct dentry *drm_fs_mount(struct file_system_type *fs_type, int flags,
 				   const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type,
-			    "drm:",
-			    NULL,
-			    NULL,
-			    0x010203ff);
+	return mount_pseudo(fs_type, NULL, NULL, 0x010203ff);
 }
 
 static struct file_system_type drm_fs_type = {

drivers/misc/cxl/api.c

@@ -40,8 +40,7 @@ static struct vfsmount *cxl_vfs_mount;
 static struct dentry *cxl_fs_mount(struct file_system_type *fs_type, int flags,
 				const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "cxl:", NULL, NULL,
-			CXL_PSEUDO_FS_MAGIC);
+	return mount_pseudo(fs_type, NULL, NULL, CXL_PSEUDO_FS_MAGIC);
 }
 
 static struct file_system_type cxl_fs_type = {

drivers/scsi/cxlflash/ocxl_hw.c

@@ -48,8 +48,7 @@ static struct dentry *ocxlflash_fs_mount(struct file_system_type *fs_type,
 					 int flags, const char *dev_name,
 					 void *data)
 {
-	return mount_pseudo(fs_type, "ocxlflash:", NULL, NULL,
-			    OCXLFLASH_FS_MAGIC);
+	return mount_pseudo(fs_type, NULL, NULL, OCXLFLASH_FS_MAGIC);
 }
 
 static struct file_system_type ocxlflash_fs_type = {

drivers/virtio/virtio_balloon.c

@@ -761,8 +761,7 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 static struct dentry *balloon_mount(struct file_system_type *fs_type,
 		int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "balloon-kvm:", NULL, NULL,
-				BALLOON_KVM_MAGIC);
+	return mount_pseudo(fs_type, NULL, NULL, BALLOON_KVM_MAGIC);
 }
 
 static struct file_system_type balloon_fs = {

fs/aio.c

@@ -252,8 +252,7 @@ static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
 static struct dentry *aio_mount(struct file_system_type *fs_type,
 				int flags, const char *dev_name, void *data)
 {
-	struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, NULL,
-					   AIO_RING_MAGIC);
+	struct dentry *root = mount_pseudo(fs_type, NULL, NULL, AIO_RING_MAGIC);
 
 	if (!IS_ERR(root))
 		root->d_sb->s_iflags |= SB_I_NOEXEC;

fs/anon_inodes.c

@@ -41,8 +41,8 @@ static const struct dentry_operations anon_inodefs_dentry_operations = {
 static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
 				int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "anon_inode:", NULL,
-			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+	return mount_pseudo(fs_type, NULL, &anon_inodefs_dentry_operations,
+			    ANON_INODE_FS_MAGIC);
 }
 
 static struct file_system_type anon_inode_fs_type = {

fs/block_dev.c

@@ -837,7 +837,7 @@ static struct dentry *bd_mount(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data)
 {
 	struct dentry *dent;
-	dent = mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC);
+	dent = mount_pseudo(fs_type, &bdev_sops, NULL, BDEVFS_MAGIC);
 	if (!IS_ERR(dent))
 		dent->d_sb->s_iflags |= SB_I_CGROUPWB;
 	return dent;

fs/btrfs/tests/btrfs-tests.c

@@ -36,7 +36,7 @@ static struct dentry *btrfs_test_mount(struct file_system_type *fs_type,
 				       int flags, const char *dev_name,
 				       void *data)
 {
-	return mount_pseudo(fs_type, "btrfs_test:", &btrfs_test_super_ops,
+	return mount_pseudo(fs_type, &btrfs_test_super_ops,
 			    NULL, BTRFS_TEST_MAGIC);
 }
 

fs/libfs.c

@@ -239,14 +239,12 @@ static const struct super_operations simple_super_operations = {
  * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that
  * will never be mountable)
  */
-struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
+struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type,
 	const struct super_operations *ops, const struct xattr_handler **xattr,
 	const struct dentry_operations *dops, unsigned long magic)
 {
 	struct super_block *s;
-	struct dentry *dentry;
 	struct inode *root;
-	struct qstr d_name = QSTR_INIT(name, strlen(name));
 
 	s = sget_userns(fs_type, NULL, set_anon_super, SB_KERNMOUNT|SB_NOUSER,
 			&init_user_ns, NULL);
@@ -271,13 +269,9 @@ struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
 	root->i_ino = 1;
 	root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
 	root->i_atime = root->i_mtime = root->i_ctime = current_time(root);
-	dentry = __d_alloc(s, &d_name);
-	if (!dentry) {
-		iput(root);
+	s->s_root = d_make_root(root);
+	if (!s->s_root)
 		goto Enomem;
-	}
-	d_instantiate(dentry, root);
-	s->s_root = dentry;
 	s->s_d_op = dops;
 	s->s_flags |= SB_ACTIVE;
 	return dget(s->s_root);

fs/nsfs.c

@@ -261,7 +261,7 @@ static const struct super_operations nsfs_ops = {
 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
 			int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
+	return mount_pseudo(fs_type, &nsfs_ops,
 			&ns_dentry_operations, NSFS_MAGIC);
 }
 static struct file_system_type nsfs = {

fs/pipe.c

@@ -1185,7 +1185,7 @@ static const struct super_operations pipefs_ops = {
 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
 			 int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
+	return mount_pseudo(fs_type, &pipefs_ops,
 			&pipefs_dentry_operations, PIPEFS_MAGIC);
 }
 

include/linux/fs.h

@@ -2257,18 +2257,18 @@ struct super_block *sget(struct file_system_type *type,
 			int (*test)(struct super_block *,void *),
 			int (*set)(struct super_block *,void *),
 			int flags, void *data);
-extern struct dentry *mount_pseudo_xattr(struct file_system_type *, char *,
+extern struct dentry *mount_pseudo_xattr(struct file_system_type *,
 					 const struct super_operations *ops,
 					 const struct xattr_handler **xattr,
 					 const struct dentry_operations *dops,
 					 unsigned long);
 
 static inline struct dentry *
-mount_pseudo(struct file_system_type *fs_type, char *name,
+mount_pseudo(struct file_system_type *fs_type,
 	     const struct super_operations *ops,
 	     const struct dentry_operations *dops, unsigned long magic)
 {
-	return mount_pseudo_xattr(fs_type, name, ops, NULL, dops, magic);
+	return mount_pseudo_xattr(fs_type, ops, NULL, dops, magic);
 }
 
 /* Alas, no aliases. Too much hassle with bringing module.h everywhere */

mm/z3fold.c

@@ -242,7 +242,7 @@ static inline void free_handle(unsigned long handle)
 static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
 				int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "z3fold:", NULL, NULL, 0x33);
+	return mount_pseudo(fs_type, NULL, NULL, 0x33);
 }
 
 static struct file_system_type z3fold_fs = {

mm/zsmalloc.c

@@ -1817,7 +1817,7 @@ static void lock_zspage(struct zspage *zspage)
 static struct dentry *zs_mount(struct file_system_type *fs_type,
 				int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo(fs_type, "zsmalloc:", NULL, NULL, ZSMALLOC_MAGIC);
+	return mount_pseudo(fs_type, NULL, NULL, ZSMALLOC_MAGIC);
 }
 
 static struct file_system_type zsmalloc_fs = {

net/socket.c

@@ -362,7 +362,7 @@ static const struct xattr_handler *sockfs_xattr_handlers[] = {
 static struct dentry *sockfs_mount(struct file_system_type *fs_type,
 			 int flags, const char *dev_name, void *data)
 {
-	return mount_pseudo_xattr(fs_type, "socket:", &sockfs_ops,
+	return mount_pseudo_xattr(fs_type, &sockfs_ops,
 				  sockfs_xattr_handlers,
 				  &sockfs_dentry_operations, SOCKFS_MAGIC);
 }