btrfs: remove new_dirid argument from btrfs_create_subvol_root

It's no longer used. While at it also remove new_dirid in create_subvol
as it's used in a single place and open code it. No functional changes.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3107,8 +3107,7 @@ int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
 			      struct extent_state **cached_state);
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
-			     struct btrfs_root *parent_root,
-			     u64 new_dirid);
+			     struct btrfs_root *parent_root);
  void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
 			       unsigned *bits);
 void btrfs_clear_delalloc_extent(struct inode *inode,

fs/btrfs/inode.c

@@ -8592,8 +8592,7 @@ static int btrfs_truncate(struct inode *inode, bool skip_writeback)
  */
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
-			     struct btrfs_root *parent_root,
-			     u64 new_dirid)
+			     struct btrfs_root *parent_root)
 {
 	struct inode *inode;
 	int err;

fs/btrfs/ioctl.c

@@ -606,7 +606,6 @@ static noinline int create_subvol(struct inode *dir,
 	int err;
 	dev_t anon_dev = 0;
 	u64 objectid;
-	u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
 	u64 index = 0;
 
 	root_item = kzalloc(sizeof(*root_item), GFP_KERNEL);
@@ -693,7 +692,7 @@ static noinline int create_subvol(struct inode *dir,
 	free_extent_buffer(leaf);
 	leaf = NULL;
 
-	btrfs_set_root_dirid(root_item, new_dirid);
+	btrfs_set_root_dirid(root_item, BTRFS_FIRST_FREE_OBJECTID);
 
 	key.objectid = objectid;
 	key.offset = 0;
@@ -716,7 +715,7 @@ static noinline int create_subvol(struct inode *dir,
 
 	btrfs_record_root_in_trans(trans, new_root);
 
-	ret = btrfs_create_subvol_root(trans, new_root, root, new_dirid);
+	ret = btrfs_create_subvol_root(trans, new_root, root);
 	btrfs_put_root(new_root);
 	if (ret) {
 		/* We potentially lose an unused inode item here */