Re: [PATCH] dax: remove VM_MIXEDMAP for fsdax and device dax

[Dan Williams <dan.j.williams@intel.com>]

On Fri, Jun 8, 2018 at 10:00 AM, Dave Jiang <dave.jiang@intel.com> wrote:
> This patch is reworked from an earlier patch that Dan has posted:
> https://patchwork.kernel.org/patch/10131727/
>
> VM_MIXEDMAP is used by dax to direct mm paths like vm_normal_page() that
> the memory page it is dealing with is not typical memory from the linear
> map. The get_user_pages_fast() path, since it does not resolve the vma,
> is already using {pte,pmd}_devmap() as a stand-in for VM_MIXEDMAP, so we
> use that as a VM_MIXEDMAP replacement in some locations. In the cases
> where there is no pte to consult we fallback to using vma_is_dax() to
> detect the VM_MIXEDMAP special case.
>
> Now that we have explicit driver pfn_t-flag opt-in/opt-out for
> get_user_pages() support for DAX we can stop setting VM_MIXEDMAP.  This
> also means we no longer need to worry about safely manipulating vm_flags
> in a future where we support dynamically changing the dax mode of a
> file.
>
> DAX should also now be supported with madvise_behavior(), vma_merge(),
> and copy_page_range().
>
> This patch has been tested against ndctl unit test. It has also been
> tested against xfstests commit: 625515d using fake pmem created by memmap
> and no additional issues have been observed.
>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Acked-by: Dan Williams <dan.j.williams@intel.com>