> +long get_user_pages_longterm(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages,
> + struct vm_area_struct **vmas)
> +{
> + struct vm_area_struct **__vmas = vmas;
How about calling the vma argument vma_arg, and the one used vma to
make thigns a little more readable?
> + struct vm_area_struct *vma_prev = NULL;
> + long rc, i;
> +
> + if (!pages)
> + return -EINVAL;
> +
> + if (!vmas && IS_ENABLED(CONFIG_FS_DAX)) {
> + __vmas = kzalloc(sizeof(struct vm_area_struct *) * nr_pages,
> + GFP_KERNEL);
> + if (!__vmas)
> + return -ENOMEM;
> + }
> +
> + rc = get_user_pages(start, nr_pages, gup_flags, pages, __vmas);
> +
> + /* skip scan for fs-dax vmas if they are compile time disabled */
> + if (!IS_ENABLED(CONFIG_FS_DAX))
> + goto out;
Instead of all this IS_ENABLED magic I'd recomment to just conditionally
compile this function and define it to get_user_pages in the header
if FS_DAX is disabled.
Else this looks fine to me.