btrfs: don't pass tree_id in btrfs_search_path_in_tree()

The 'tree_id' parameter in btrfs_search_path_in_tree() was only being
used in order to fetch the root tree to be considered for the
search. For this same reason this function was also requiring a 'struct
btrfs_fs_info' parameter. This commit replaces these two parameters with
a single 'struct btrfs_root' one, which identifies from which root tree
the search should happen.

This function only has one caller, the inode lookup ioctl, which knows
how to provide the root tree for each case. In fact, if args->treeid ==
0, then we don't even have to allocate a new root tree object, and we
can reuse the one provided by the ioctl system call, thus avoiding an
extra allocation.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: mssola

fs/btrfs/ioctl.c

@@ -1664,13 +1664,11 @@ static noinline int btrfs_ioctl_tree_search_v2(struct btrfs_root *root,
 }
 
 /*
- * Search INODE_REFs to identify path name of 'dirid' directory
- * in a 'tree_id' tree. and sets path name to 'name'.
+ * Search for an INODE_REF in a 'root' tree which identifies the path name of
+ * 'dirid'. When found, it sets 'name' with the path name.
  */
-static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
-				u64 tree_id, u64 dirid, char *name)
+static noinline int btrfs_search_path_in_tree(struct btrfs_root *root, u64 dirid, char *name)
 {
-	struct btrfs_root *root;
 	struct btrfs_key key;
 	char *ptr;
 	int ret = -1;
@@ -1692,25 +1690,16 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 
 	ptr = &name[BTRFS_INO_LOOKUP_PATH_MAX - 1];
 
-	root = btrfs_get_fs_root(info, tree_id, true);
-	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		root = NULL;
-		goto out;
-	}
-
 	key.objectid = dirid;
 	key.type = BTRFS_INODE_REF_KEY;
 	key.offset = (u64)-1;
 
 	while (1) {
 		ret = btrfs_search_backwards(root, &key, path);
 		if (ret < 0)
-			goto out;
-		else if (ret > 0) {
-			ret = -ENOENT;
-			goto out;
-		}
+			return ret;
+		else if (ret > 0)
+			return -ENOENT;
 
 		l = path->nodes[0];
 		slot = path->slots[0];
@@ -1719,10 +1708,8 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 		len = btrfs_inode_ref_name_len(l, iref);
 		ptr -= len + 1;
 		total_len += len + 1;
-		if (ptr < name) {
-			ret = -ENAMETOOLONG;
-			goto out;
-		}
+		if (ptr < name)
+			return -ENAMETOOLONG;
 
 		*(ptr + len) = '/';
 		read_extent_buffer(l, ptr, (unsigned long)(iref + 1), len);
@@ -1737,10 +1724,8 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 	}
 	memmove(name, ptr, total_len);
 	name[total_len] = '\0';
-	ret = 0;
-out:
-	btrfs_put_root(root);
-	return ret;
+
+	return 0;
 }
 
 static int btrfs_search_path_in_tree_user(struct mnt_idmap *idmap,
@@ -1884,6 +1869,7 @@ static int btrfs_search_path_in_tree_user(struct mnt_idmap *idmap,
 static noinline int btrfs_ioctl_ino_lookup(struct btrfs_root *root,
 					   void __user *argp)
 {
+	bool new_root = false;
 	struct btrfs_ioctl_ino_lookup_args AUTO_KFREE(args);
 	int ret = 0;
 
@@ -1897,6 +1883,8 @@ static noinline int btrfs_ioctl_ino_lookup(struct btrfs_root *root,
 	 */
 	if (args->treeid == 0)
 		args->treeid = btrfs_root_id(root);
+	else
+		new_root = true;
 
 	if (args->objectid == BTRFS_FIRST_FREE_OBJECTID) {
 		args->name[0] = 0;
@@ -1908,9 +1896,14 @@ static noinline int btrfs_ioctl_ino_lookup(struct btrfs_root *root,
 		goto out;
 	}
 
-	ret = btrfs_search_path_in_tree(root->fs_info,
-					args->treeid, args->objectid,
-					args->name);
+	if (new_root) {
+		root = btrfs_get_fs_root(root->fs_info, args->treeid, true);
+		if (IS_ERR(root))
+			return PTR_ERR(root);
+	}
+	ret = btrfs_search_path_in_tree(root, args->objectid, args->name);
+	if (new_root)
+		btrfs_put_root(root);
 
 out:
 	if (ret == 0 && copy_to_user(argp, args, sizeof(*args)))