Re: [PATCH] mm: hugetlb: kill set_huge_swap_pte_at()

The commit e5251fd43007 ("mm/hugetlb: introduce set_huge_swap_pte_at()
helper") add set_huge_swap_pte_at() to handle swap entries on
architectures that support hugepages consisting of contiguous ptes.
And currently the set_huge_swap_pte_at() is only overridden by arm64.

The set_huge_swap_pte_at() provide a sz parameter to help determine
the number of entries to be updated. But in fact, all hugetlb swap
entries contain pfn information, so we can find the corresponding
folio through the pfn recorded in the swap entry, then the folio_size()
is the number of entries that need to be updated.

And considering that users will easily cause bugs by ignoring the
difference between set_huge_swap_pte_at() and set_huge_pte_at().
Let's handle swap entries in set_huge_pte_at() and remove the
set_huge_swap_pte_at(), then we can call set_huge_pte_at()
anywhere, which simplifies our coding.

Signed-off-by: Qi Zheng <redacted>
---
 arch/arm64/include/asm/hugetlb.h |  3 ---
 arch/arm64/mm/hugetlbpage.c      | 34 ++++++++++++++++----------------
 include/linux/hugetlb.h          | 13 ------------
 mm/hugetlb.c                     |  8 +++-----
 mm/rmap.c                        | 11 +++--------
 5 files changed, 23 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index 1fd2846dbefe..d20f5da2d76f 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h

@@ -46,9 +46,6 @@ extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
 			   pte_t *ptep, unsigned long sz);
 #define __HAVE_ARCH_HUGE_PTEP_GET
 extern pte_t huge_ptep_get(pte_t *ptep);
-extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
-				 pte_t *ptep, pte_t pte, unsigned long sz);
-#define set_huge_swap_pte_at set_huge_swap_pte_at
 
 void __init arm64_hugetlb_cma_reserve(void);
 

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index c9e076683e5d..58b89b9d13e0 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c

@@ -238,6 +238,13 @@ static void clear_flush(struct mm_struct *mm,
 	flush_tlb_range(&vma, saddr, addr);
 }
 
+static inline struct folio *hugetlb_swap_entry_to_folio(swp_entry_t entry)
+{
+	VM_BUG_ON(!is_migration_entry(entry) && !is_hwpoison_entry(entry));
+
+	return page_folio(pfn_to_page(swp_offset(entry)));
+}