Re: [PATCH 2/3] dax: stop using VM_MIXEDMAP for dax

[Jeff Moyer <jmoyer@redhat.com>]

Dan Williams <dan.j.williams@intel.com> writes:

> Now that we always have pages for DAX we can stop setting VM_MIXEDMAP.
> This does require some small fixups for the pte insert routines that dax
> utilizes.

It used to be that userspace would look to see if it had a 'mm' entry in
/proc/pid/smaps to determine whether or not it got a direct mapping.
Later, that same userspace (nvml) just uniformly declared dax not
available from any Linux file system, since msync was required.  And, I
guess DAX has always been marked experimental, so the interface can be
changed.

All this is to say I guess it's fine to change this.

> diff --git a/mm/mmap.c b/mm/mmap.c
> index 680506faceae..d682f60670ff 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1111,7 +1111,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
>  	 * We later require that vma->vm_flags == vm_flags,
>  	 * so this tests vma->vm_flags & VM_SPECIAL, too.
>  	 */
> -	if (vm_flags & VM_SPECIAL)
> +	if ((vm_flags & VM_SPECIAL))
>  		return NULL;

That looks superfluous.

-Jeff

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