Alistair Popple wrote: > > Alistair Popple <apopple@xxxxxxxxxx> writes: > > > Dan Williams <dan.j.williams@xxxxxxxxx> writes: > > > >> Alistair Popple wrote: > > > > I also noticed folio_anon() is not safe to call on a FS DAX page due to > > sharing PAGE_MAPPING_DAX_SHARED. > > Also it feels like I could be missing something here. AFAICT the > page->mapping and page->index fields can't actually be used outside of > fs/dax because they are overloaded for the shared case. Therefore > setting/clearing them could be skipped and the only reason for doing so > is so dax_associate_entry()/dax_disassociate_entry() can generate > warnings which should never occur anyway. So all that code is > functionally unnecessary. What do you mean outside of fs/dax, do you literally mean outside of fs/dax.c, or the devdax case (i.e. dax without fs-entanglements)? Memory failure needs ->mapping and ->index to rmap dax pages. See mm/memory-failure.c::__add_to_kill() and mm/memory-failure.c::__add_to_kill_fsdax() where that latter one is for cases where the fs needs has signed up to react to dax page failure.
