btrfs: simplify some assignments of inode numbers

There are several places when the btrfs inode is converted to the
generic inode, back to btrfs and then passed to btrfs_ino. We can remove
the extra back and forth conversions.
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -4242,9 +4242,9 @@ static void btrfs_prune_dentries(struct btrfs_root *root)
 		prev = node;
 		entry = rb_entry(node, struct btrfs_inode, rb_node);
 
-		if (objectid < btrfs_ino(BTRFS_I(&entry->vfs_inode)))
+		if (objectid < btrfs_ino(entry))
 			node = node->rb_left;
-		else if (objectid > btrfs_ino(BTRFS_I(&entry->vfs_inode)))
+		else if (objectid > btrfs_ino(entry))
 			node = node->rb_right;
 		else
 			break;
@@ -4252,7 +4252,7 @@ static void btrfs_prune_dentries(struct btrfs_root *root)
 	if (!node) {
 		while (prev) {
 			entry = rb_entry(prev, struct btrfs_inode, rb_node);
-			if (objectid <= btrfs_ino(BTRFS_I(&entry->vfs_inode))) {
+			if (objectid <= btrfs_ino(entry)) {
 				node = prev;
 				break;
 			}
@@ -4261,7 +4261,7 @@ static void btrfs_prune_dentries(struct btrfs_root *root)
 	}
 	while (node) {
 		entry = rb_entry(node, struct btrfs_inode, rb_node);
-		objectid = btrfs_ino(BTRFS_I(&entry->vfs_inode)) + 1;
+		objectid = btrfs_ino(entry) + 1;
 		inode = igrab(&entry->vfs_inode);
 		if (inode) {
 			spin_unlock(&root->inode_lock);
@@ -5614,9 +5614,9 @@ static void inode_tree_add(struct inode *inode)
 		parent = *p;
 		entry = rb_entry(parent, struct btrfs_inode, rb_node);
 
-		if (ino < btrfs_ino(BTRFS_I(&entry->vfs_inode)))
+		if (ino < btrfs_ino(entry))
 			p = &parent->rb_left;
-		else if (ino > btrfs_ino(BTRFS_I(&entry->vfs_inode)))
+		else if (ino > btrfs_ino(entry))
 			p = &parent->rb_right;
 		else {
 			WARN_ON(!(entry->vfs_inode.i_state &