A lot of d_add() uses are in ->lookup() instances; those really should be d_splice_alias() - that's mandatory for anything exported (and we'd seen people not bothering to convert when adding exports/open-by-fhandle support) *and* it's not costlier than d_add() anyway, in all cases when d_add() wouldn't have caused instant breakage. What's more, d_splice_alias() makes for simpler life in callers - it does the right thing when given ERR_PTR(), which simplifies the logics in quite a few ->lookup() instances. There are trickier cases, but a bunch of those call sites are completely straightforward. See followups, or vfs.git#work.lookup
