Alistair Popple wrote: > Currently dax is the only user of pmd and pud mapped ZONE_DEVICE > pages. Therefore page walkers that want to exclude DAX pages can check > pmd_devmap or pud_devmap. However soon dax will no longer set PFN_DEV, > meaning dax pages are mapped as normal pages. > > Ensure page walkers that currently use pXd_devmap to skip DAX pages > continue to do so by adding explicit checks of the VMA instead.
tl;dr: Reviewed-by: Dan Williams <dan.j.willi...@intel.com> So I went through all the p[mu]d_devmap() checks and indeed this is the set I also come up with that are implicitly checking for "dax" instead of checking for "is this a larger than base pte size mapping". While I am a little uncomfortable with the generality of calling the policy "dax" in these locations I think it is ok for now. I.e. the fundamental detail in these paths is "huge pte, but not typical page-allocator THP page" Also I would have felt better if some of the leftover places that are doing "dax" checks but not updated were noted in the changelog just for review purposes. Like: "Note paths like follow_huge_pud and follow_pmd_mask also have 'dax' checks, but those paths are for maintaining dev_pagemap refcounts which no longer (since v6.15) need to be managed for dax pages. A later patch cleans those up."
