Re: [PATCH v4 4/4] mm/hugetlb: Convert use of struct page to folio in __unmap_hugepage_range()

[Andrew Morton <akpm@linux-foundation.org>]

On Mon,  5 May 2025 11:22:44 -0700 nifan.cxl@gmail.com wrote:

> From: Fan Ni <fan.ni@samsung.com>
> 
> In __unmap_hugepage_range(), the "page" pointer always points to the
> first page of a huge page, which guarantees there is a folio associating
> with it.  Convert the "page" pointer to use folio.
> 
> ...
>
>  		 * Restore the reservation for anonymous page, otherwise the
> @@ -5950,8 +5951,8 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  		 * reservation bit.
>  		 */
>  		if (!h->surplus_huge_pages && __vma_private_lock(vma) &&
> -		    folio_test_anon(page_folio(page))) {
> -			folio_set_hugetlb_restore_reserve(page_folio(page));
> +		    folio_test_anon(folio)) {
> +			folio_set_hugetlb_restore_reserve(folio);
>  			/* Reservation to be adjusted after the spin lock */
>  			adjust_reservation = true;
>  		}
> @@ -5975,16 +5976,17 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  				 * count will not be incremented by free_huge_folio.
>  				 * Act as if we consumed the reservation.
>  				 */

I did not enjoy reading the above comment, so I did this to it.

The comment would be better if it described why we "Act as if we
consumed the reservation.".  "why, not what".


From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm/hugetlb.c: __unmap_hugepage_range(): comment cleanup
Date: Mon May  5 02:54:25 PM PDT 2025

Wrap to 80 cols, fix a typo, use regular layout, parenthesize function
identifiers, fix grammar and add braces.

Cc: David Hildenbrand <david@redhat.com>
Cc: Fan Ni <fan.ni@samsung.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlbc-__unmap_hugepage_range-comment-cleanup
+++ a/mm/hugetlb.c
@@ -5969,16 +5969,19 @@ void __unmap_hugepage_range(struct mmu_g
 		if (adjust_reservation) {
 			int rc = vma_needs_reservation(h, vma, address);
 
-			if (rc < 0)
-				/* Pressumably allocate_file_region_entries failed
-				 * to allocate a file_region struct. Clear
-				 * hugetlb_restore_reserve so that global reserve
-				 * count will not be incremented by free_huge_folio.
-				 * Act as if we consumed the reservation.
+			if (rc < 0) {
+				/*
+				 * Presumably allocate_file_region_entries()
+				 * failed to allocate a file_region struct.
+				 * Clear hugetlb_restore_reserve so that the
+				 * global reserve count will not be incremented
+				 * by free_huge_folio().  Act as if we consumed
+				 * the reservation.
 				 */
 				folio_clear_hugetlb_restore_reserve(folio);
-			else if (rc)
+			} else if (rc) {
 				vma_add_reservation(h, vma, address);
+			}
 		}
 
 		tlb_remove_page_size(tlb, folio_page(folio, 0),
_