[PATCH v3] hugetlb: simplify hugetlb handling in follow_page_mask

[Baolin Wang]

On 9/19/2022 10:13 AM, Mike Kravetz wrote:
> During discussions of this series [1], it was suggested that hugetlb
> handling code in follow_page_mask could be simplified.  At the beginning
> of follow_page_mask, there currently is a call to follow_huge_addr which
> 'may' handle hugetlb pages.  ia64 is the only architecture which provides
> a follow_huge_addr routine that does not return error.  Instead, at each
> level of the page table a check is made for a hugetlb entry.  If a hugetlb
> entry is found, a call to a routine associated with that entry is made.
> 
> Currently, there are two checks for hugetlb entries at each page table
> level.  The first check is of the form:
>          if (p?d_huge())
>                  page = follow_huge_p?d();
> the second check is of the form:
>          if (is_hugepd())
>                  page = follow_huge_pd().
> 
> We can replace these checks, as well as the special handling routines
> such as follow_huge_p?d() and follow_huge_pd() with a single routine to
> handle hugetlb vmas.
> 
> A new routine hugetlb_follow_page_mask is called for hugetlb vmas at the
> beginning of follow_page_mask.  hugetlb_follow_page_mask will use the
> existing routine huge_pte_offset to walk page tables looking for hugetlb
> entries.  huge_pte_offset can be overwritten by architectures, and already
> handles special cases such as hugepd entries.
> 
> [1] https://lore.kernel.org/linux-mm/cover.1661240170.git.baolin.wang@linux.alibaba.com/
> 
> Suggested-by: David Hildenbrand <david at redhat.com>
> Signed-off-by: Mike Kravetz <mike.kravetz at oracle.com>

LGTM, and works well on my machine. So feel free to add:
Reviewed-by: Baolin Wang <baolin.wang at linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang at linux.alibaba.com>