The patch titled
Subject: mm/ksm: convert break_ksm() from walk_page_range_vma() to folio_walk
has been added to the -mm mm-unstable branch. Its filename is
mm-ksm-convert-break_ksm-from-walk_page_range_vma-to-folio_walk.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ksm-convert-break_ksm-from-walk_page_range_vma-to-folio_walk.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/ksm: convert break_ksm() from walk_page_range_vma() to folio_walk
Date: Fri, 2 Aug 2024 17:55:24 +0200
Let's simplify by reusing folio_walk. Keep the existing behavior by
handling migration entries and zeropages.
Link: https://lkml.kernel.org/r/20240802155524.517137-12-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Janosch Frank <frankja@xxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 63 +++++++++++++----------------------------------------
1 file changed, 16 insertions(+), 47 deletions(-)
--- a/mm/ksm.c~mm-ksm-convert-break_ksm-from-walk_page_range_vma-to-folio_walk
+++ a/mm/ksm.c
@@ -608,47 +608,6 @@ static inline bool ksm_test_exit(struct
return atomic_read(&mm->mm_users) == 0;
}
-static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long next,
- struct mm_walk *walk)
-{
- struct page *page = NULL;
- spinlock_t *ptl;
- pte_t *pte;
- pte_t ptent;
- int ret;
-
- pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
- if (!pte)
- return 0;
- ptent = ptep_get(pte);
- if (pte_present(ptent)) {
- page = vm_normal_page(walk->vma, addr, ptent);
- } else if (!pte_none(ptent)) {
- swp_entry_t entry = pte_to_swp_entry(ptent);
-
- /*
- * As KSM pages remain KSM pages until freed, no need to wait
- * here for migration to end.
- */
- if (is_migration_entry(entry))
- page = pfn_swap_entry_to_page(entry);
- }
- /* return 1 if the page is an normal ksm page or KSM-placed zero page */
- ret = (page && PageKsm(page)) || is_ksm_zero_pte(ptent);
- pte_unmap_unlock(pte, ptl);
- return ret;
-}
-
-static const struct mm_walk_ops break_ksm_ops = {
- .pmd_entry = break_ksm_pmd_entry,
- .walk_lock = PGWALK_RDLOCK,
-};
-
-static const struct mm_walk_ops break_ksm_lock_vma_ops = {
- .pmd_entry = break_ksm_pmd_entry,
- .walk_lock = PGWALK_WRLOCK,
-};
-
/*
* We use break_ksm to break COW on a ksm page by triggering unsharing,
* such that the ksm page will get replaced by an exclusive anonymous page.
@@ -665,16 +624,26 @@ static const struct mm_walk_ops break_ks
static int break_ksm(struct vm_area_struct *vma, unsigned long addr, bool lock_vma)
{
vm_fault_t ret = 0;
- const struct mm_walk_ops *ops = lock_vma ?
- &break_ksm_lock_vma_ops : &break_ksm_ops;
+
+ if (lock_vma)
+ vma_start_write(vma);
do {
- int ksm_page;
+ bool ksm_page = false;
+ struct folio_walk fw;
+ struct folio *folio;
cond_resched();
- ksm_page = walk_page_range_vma(vma, addr, addr + 1, ops, NULL);
- if (WARN_ON_ONCE(ksm_page < 0))
- return ksm_page;
+ folio = folio_walk_start(&fw, vma, addr,
+ FW_MIGRATION | FW_ZEROPAGE);
+ if (folio) {
+ /* Small folio implies FW_LEVEL_PTE. */
+ if (!folio_test_large(folio) &&
+ (folio_test_ksm(folio) || is_ksm_zero_pte(fw.pte)))
+ ksm_page = true;
+ folio_walk_end(&fw, vma);
+ }
+
if (!ksm_page)
return 0;
ret = handle_mm_fault(vma, addr,
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-turn-use_split_pte_ptlocks-use_split_pte_ptlocks-into-kconfig-options.patch
mm-hugetlb-enforce-that-pmd-pt-sharing-has-split-pmd-pt-locks.patch
powerpc-8xx-document-and-enforce-that-split-pt-locks-are-not-used.patch
mm-simplify-arch_make_folio_accessible.patch
mm-gup-convert-to-arch_make_folio_accessible.patch
s390-uv-drop-arch_make_page_accessible.patch
mm-hugetlb-remove-hugetlb_follow_page_mask-leftover.patch
mm-rmap-cleanup-partially-mapped-handling-in-__folio_remove_rmap.patch
mm-clarify-folio_likely_mapped_shared-documentation-for-ksm-folios.patch
mm-provide-vm_normal_pagefolio_pmd-with-config_pgtable_has_huge_leaves.patch
mm-pagewalk-introduce-folio_walk_start-folio_walk_end.patch
mm-migrate-convert-do_pages_stat_array-from-follow_page-to-folio_walk.patch
mm-migrate-convert-add_page_for_migration-from-follow_page-to-folio_walk.patch
mm-ksm-convert-get_mergeable_page-from-follow_page-to-folio_walk.patch
mm-ksm-convert-scan_get_next_rmap_item-from-follow_page-to-folio_walk.patch
mm-huge_memory-convert-split_huge_pages_pid-from-follow_page-to-folio_walk.patch
s390-uv-convert-gmap_destroy_page-from-follow_page-to-folio_walk.patch
s390-mm-fault-convert-do_secure_storage_access-from-follow_page-to-folio_walk.patch
mm-remove-follow_page.patch
mm-ksm-convert-break_ksm-from-walk_page_range_vma-to-folio_walk.patch
