btrfs: rework arguments of btrfs_unlink_subvol

btrfs_unlink_subvol takes the name of the dentry and the root objectid
based on what kind of inode this is, either a real subvolume link or a
empty one that we inherited as a snapshot.  We need to fix how we unlink
in the case for BTRFS_EMPTY_SUBVOL_DIR_OBJECTID in the future, so rework
btrfs_unlink_subvol to just take the dentry and handle getting the right
objectid given the type of inode this is.  There is no functional change
here, simply pushing the work into btrfs_unlink_subvol() proper.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -4238,18 +4238,30 @@ static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
 }
 
 static int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
-			       struct inode *dir, u64 objectid,
-			       const char *name, int name_len)
+			       struct inode *dir, struct dentry *dentry)
 {
 	struct btrfs_root *root = BTRFS_I(dir)->root;
+	struct btrfs_inode *inode = BTRFS_I(d_inode(dentry));
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_dir_item *di;
 	struct btrfs_key key;
+	const char *name = dentry->d_name.name;
+	int name_len = dentry->d_name.len;
 	u64 index;
 	int ret;
+	u64 objectid;
 	u64 dir_ino = btrfs_ino(BTRFS_I(dir));
 
+	if (btrfs_ino(inode) == BTRFS_FIRST_FREE_OBJECTID) {
+		objectid = inode->root->root_key.objectid;
+	} else if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
+		objectid = inode->location.objectid;
+	} else {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
@@ -4487,8 +4499,7 @@ int btrfs_delete_subvolume(struct inode *dir, struct dentry *dentry)
 
 	btrfs_record_snapshot_destroy(trans, BTRFS_I(dir));
 
-	ret = btrfs_unlink_subvol(trans, dir, dest->root_key.objectid,
-				  dentry->d_name.name, dentry->d_name.len);
+	ret = btrfs_unlink_subvol(trans, dir, dentry);
 	if (ret) {
 		err = ret;
 		btrfs_abort_transaction(trans, ret);
@@ -4583,10 +4594,7 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
 		return PTR_ERR(trans);
 
 	if (unlikely(btrfs_ino(BTRFS_I(inode)) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
-		err = btrfs_unlink_subvol(trans, dir,
-					  BTRFS_I(inode)->location.objectid,
-					  dentry->d_name.name,
-					  dentry->d_name.len);
+		err = btrfs_unlink_subvol(trans, dir, dentry);
 		goto out;
 	}
 
@@ -9536,7 +9544,6 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 	u64 new_ino = btrfs_ino(BTRFS_I(new_inode));
 	u64 old_idx = 0;
 	u64 new_idx = 0;
-	u64 root_objectid;
 	int ret;
 	bool root_log_pinned = false;
 	bool dest_log_pinned = false;
@@ -9642,10 +9649,7 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 
 	/* src is a subvolume */
 	if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
-		root_objectid = BTRFS_I(old_inode)->root->root_key.objectid;
-		ret = btrfs_unlink_subvol(trans, old_dir, root_objectid,
-					  old_dentry->d_name.name,
-					  old_dentry->d_name.len);
+		ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
 	} else { /* src is an inode */
 		ret = __btrfs_unlink_inode(trans, root, BTRFS_I(old_dir),
 					   BTRFS_I(old_dentry->d_inode),
@@ -9661,10 +9665,7 @@ static int btrfs_rename_exchange(struct inode *old_dir,
 
 	/* dest is a subvolume */
 	if (new_ino == BTRFS_FIRST_FREE_OBJECTID) {
-		root_objectid = BTRFS_I(new_inode)->root->root_key.objectid;
-		ret = btrfs_unlink_subvol(trans, new_dir, root_objectid,
-					  new_dentry->d_name.name,
-					  new_dentry->d_name.len);
+		ret = btrfs_unlink_subvol(trans, new_dir, new_dentry);
 	} else { /* dest is an inode */
 		ret = __btrfs_unlink_inode(trans, dest, BTRFS_I(new_dir),
 					   BTRFS_I(new_dentry->d_inode),
@@ -9862,7 +9863,6 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	struct inode *new_inode = d_inode(new_dentry);
 	struct inode *old_inode = d_inode(old_dentry);
 	u64 index = 0;
-	u64 root_objectid;
 	int ret;
 	u64 old_ino = btrfs_ino(BTRFS_I(old_inode));
 	bool log_pinned = false;
@@ -9970,10 +9970,7 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 				BTRFS_I(old_inode), 1);
 
 	if (unlikely(old_ino == BTRFS_FIRST_FREE_OBJECTID)) {
-		root_objectid = BTRFS_I(old_inode)->root->root_key.objectid;
-		ret = btrfs_unlink_subvol(trans, old_dir, root_objectid,
-					old_dentry->d_name.name,
-					old_dentry->d_name.len);
+		ret = btrfs_unlink_subvol(trans, old_dir, old_dentry);
 	} else {
 		ret = __btrfs_unlink_inode(trans, root, BTRFS_I(old_dir),
 					BTRFS_I(d_inode(old_dentry)),
@@ -9992,10 +9989,7 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 		new_inode->i_ctime = current_time(new_inode);
 		if (unlikely(btrfs_ino(BTRFS_I(new_inode)) ==
 			     BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
-			root_objectid = BTRFS_I(new_inode)->location.objectid;
-			ret = btrfs_unlink_subvol(trans, new_dir, root_objectid,
-						new_dentry->d_name.name,
-						new_dentry->d_name.len);
+			ret = btrfs_unlink_subvol(trans, new_dir, new_dentry);
 			BUG_ON(new_inode->i_nlink == 0);
 		} else {
 			ret = btrfs_unlink_inode(trans, dest, BTRFS_I(new_dir),