btrfs: switch btrfs_pending_snapshot::dir to btrfs_inode

The structure is internal so we should use struct btrfs_inode for that.
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -855,7 +855,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
 	pending_snapshot->dentry = dentry;
 	pending_snapshot->root = root;
 	pending_snapshot->readonly = readonly;
-	pending_snapshot->dir = dir;
+	pending_snapshot->dir = BTRFS_I(dir);
 	pending_snapshot->inherit = inherit;
 
 	trans = btrfs_start_transaction(root, 0);

fs/btrfs/transaction.c

@@ -1637,7 +1637,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	struct btrfs_root *root = pending->root;
 	struct btrfs_root *parent_root;
 	struct btrfs_block_rsv *rsv;
-	struct inode *parent_inode = pending->dir;
+	struct inode *parent_inode = &pending->dir->vfs_inode;
 	struct btrfs_path *path;
 	struct btrfs_dir_item *dir_item;
 	struct extent_buffer *tmp;

fs/btrfs/transaction.h

@@ -172,7 +172,7 @@ struct btrfs_trans_handle {
 
 struct btrfs_pending_snapshot {
 	struct dentry *dentry;
-	struct inode *dir;
+	struct btrfs_inode *dir;
 	struct btrfs_root *root;
 	struct btrfs_root_item *root_item;
 	struct btrfs_root *snap;