+ /*
+ * In some cases (e.g. tree roots), we need to look for a given
+ * objectid and type without knowing the offset value (3rd element of a
+ * btrfs tree node key). We can rely on the fact that btrfs_search_tree
+ * returns the first element with key >= search_key, and then perform
+ * our own comparison between the returned element and the search key.
+ *
+ * It is tempting to use a search key with offset 0 to perform this
+ * "fuzzy search". This would return the first item with the (objectid,
+ * type) we're looking for. However, using offset 0 has the wrong
+ * behavior when the wanted item is the first in a leaf: since our
+ * search key will be lower than the wanted item, the recursive search
+ * will explore the wrong branch of the tree.
+ *
+ * Instead, use the largest possible offset (-1). The result of this
+ * search will either be:
+ * 1. An element with the (objectid, type) we're looking for, if it
+ * has offset -1 or if it is the last element in its leaf.
+ * 2. The first element *after* an element with the (objectid, type)
+ */