userfaultfd: convert mfill_atomic_pte_copy() to use a folio

userfaultfd: convert mfill_atomic_pte_copy() to use a folio

Patch series "userfaultfd: convert userfaultfd functions to use folios",
v5.

This series converts several userfaultfd functions to use folios.

This patch (of 6):

Call vma_alloc_folio() directly instead of alloc_page_vma() and convert
page_kaddr to kaddr in mfill_atomic_pte_copy().  Removes several calls to
compound_head().

Link: https://lkml.kernel.org/r/20230331093937.945725-1-zhangpeng362@huawei.com
Link: https://lkml.kernel.org/r/20230331093937.945725-2-zhangpeng362@huawei.com
Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>