[PATCH v5 13/16] mm/migrate: calculate large folio page index using PFN
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Date: 2026-08-13 17:37:29
Also in:
amd-gfx, dri-devel, intel-xe, kvm, linux-fsdevel, linux-kselftest, linux-mm, linux-perf-users, linux-s390, lkml
Subsystem:
memory management, memory management - memory policy and migration, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Rather than having to figure out the page index to use using linear_page_index(), calculate it using PFN. This is a more natural fit as the linear page index is immaterial to determining the folio page index. Derive the page index from the offset between migration entry PFN and folio PFN - pvmw.pfn (set via DEFINE_FOLIO_VMA_WALK() which uses folio_pfn() to obtain it). Additionally remove a not so useful comment and clean the code layout up. No functional change intended. Suggested-by: David Hildenbrand (Arm) <david@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org> --- mm/migrate.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index d08eff028483..50d0b547bca3 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c@@ -356,16 +356,11 @@ static bool remove_migration_pte(struct folio *folio, while (page_vma_mapped_walk(&pvmw)) { rmap_t rmap_flags = RMAP_NONE; - pte_t old_pte; - pte_t pte; + unsigned long idx = 0; softleaf_t entry; struct page *new; - unsigned long idx = 0; - - /* pgoff is invalid for ksm pages, but they are never large */ - if (folio_test_large(folio) && !folio_test_hugetlb(folio)) - idx = linear_page_index(vma, pvmw.address) - pvmw.pgoff; - new = folio_page(folio, idx); + pte_t old_pte; + pte_t pte; #ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES /* PMD-mapped THP migration entry */
@@ -381,14 +376,18 @@ static bool remove_migration_pte(struct folio *folio, pvmw.pte); else old_pte = ptep_get(pvmw.pte); + + entry = softleaf_from_pte(old_pte); + if (folio_test_large(folio) && !folio_test_hugetlb(folio)) + idx = softleaf_to_pfn(entry) - pvmw.pfn; + if (rmap_walk_arg->map_unused_to_zeropage && try_to_map_unused_to_zeropage(&pvmw, folio, old_pte, idx)) continue; folio_get(folio); + new = folio_page(folio, idx); pte = mk_pte(new, READ_ONCE(vma->vm_page_prot)); - - entry = softleaf_from_pte(old_pte); if (!softleaf_is_migration_young(entry)) pte = pte_mkold(pte); if (folio_test_dirty(folio) && softleaf_is_migration_dirty(entry))
--
2.55.0