+ mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page.patch added to mm-unstable branch

+ mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/migrate_device: use folio_mapcount() in migrate_vma_check_page()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page.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@redhat.com>
Subject: mm/migrate_device: use folio_mapcount() in migrate_vma_check_page()
Date: Tue, 9 Apr 2024 21:22:57 +0200

We want to limit the use of page_mapcount() to the places where it is
absolutely necessary.  Let's convert migrate_vma_check_page() to work on a
folio internally so we can remove the page_mapcount() usage.

Note that we reject any large folios.

There is a lot more folio conversion to be had, but that has to wait for
another day.  No functional change intended.

Link: https://lkml.kernel.org/r/20240409192301.907377-15-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate_device.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/mm/migrate_device.c~mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page
+++ a/mm/migrate_device.c
@@ -324,6 +324,8 @@ static void migrate_vma_collect(struct m
  */
 static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
 {
+	struct folio *folio = page_folio(page);
+
 	/*
 	 * One extra ref because caller holds an extra reference, either from
 	 * isolate_lru_page() for a regular page, or migrate_vma_collect() for
@@ -336,18 +338,18 @@ static bool migrate_vma_check_page(struc
 	 * check them than regular pages, because they can be mapped with a pmd
 	 * or with a pte (split pte mapping).
 	 */
-	if (PageCompound(page))
+	if (folio_test_large(folio))
 		return false;
 
 	/* Page from ZONE_DEVICE have one extra reference */
-	if (is_zone_device_page(page))
+	if (folio_is_zone_device(folio))
 		extra++;
 
 	/* For file back page */
-	if (page_mapping(page))
-		extra += 1 + page_has_private(page);
+	if (folio_mapping(folio))
+		extra += 1 + folio_has_private(folio);
 
-	if ((page_count(page) - extra) > page_mapcount(page))
+	if ((folio_ref_count(folio) - extra) > folio_mapcount(folio))
 		return false;
 
 	return true;
_

Patches currently in -mm which might be from david@redhat.com are

mm-madvise-make-madv_populate_readwrite-handle-vm_fault_retry-properly.patch
mm-madvise-dont-perform-madvise-vma-walk-for-madv_populate_readwrite.patch
mm-userfaultfd-dont-place-zeropages-when-zeropages-are-disallowed.patch
s390-mm-re-enable-the-shared-zeropage-for-pv-and-skeys-kvm-guests.patch
mm-convert-folio_estimated_sharers-to-folio_likely_mapped_shared.patch
mm-convert-folio_estimated_sharers-to-folio_likely_mapped_shared-fix.patch
selftests-memfd_secret-add-vmsplice-test.patch
mm-merge-folio_is_secretmem-and-folio_fast_pin_allowed-into-gup_fast_folio_allowed.patch
mm-optimize-config_per_vma_lock-member-placement-in-vm_area_struct.patch
mm-remove-prot-parameter-from-move_pte.patch
mm-gup-consistently-name-gup-fast-functions.patch
mm-treewide-rename-config_have_fast_gup-to-config_have_gup_fast.patch
mm-use-gup-fast-instead-fast-gup-in-remaining-comments.patch
drivers-virt-acrn-fix-pfnmap-pte-checks-in-acrn_vm_ram_map.patch
mm-pass-vma-instead-of-mm-to-follow_pte.patch
mm-follow_pte-improvements.patch
mm-allow-for-detecting-underflows-with-page_mapcount-again.patch
mm-rmap-always-inline-anon-file-rmap-duplication-of-a-single-pte.patch
mm-rmap-add-fast-path-for-small-folios-when-adding-removing-duplicating.patch
mm-track-mapcount-of-large-folios-in-single-value.patch
mm-improve-folio_likely_mapped_shared-using-the-mapcount-of-large-folios.patch
mm-make-folio_mapcount-return-0-for-small-typed-folios.patch
mm-memory-use-folio_mapcount-in-zap_present_folio_ptes.patch
mm-huge_memory-use-folio_mapcount-in-zap_huge_pmd-sanity-check.patch
mm-memory-failure-use-folio_mapcount-in-hwpoison_user_mappings.patch
mm-page_alloc-use-folio_mapped-in-__alloc_contig_migrate_range.patch
mm-migrate-use-folio_likely_mapped_shared-in-add_page_for_migration.patch
sh-mm-cache-use-folio_mapped-in-copy_from_user_page.patch
mm-filemap-use-folio_mapcount-in-filemap_unaccount_folio.patch
mm-migrate_device-use-folio_mapcount-in-migrate_vma_check_page.patch
trace-events-page_ref-trace-the-raw-page-mapcount-value.patch
xtensa-mm-convert-check_tlb_entry-to-sanity-check-folios.patch
mm-debug-print-only-page-mapcount-excluding-folio-entire-mapcount-in-__dump_folio.patch
documentation-admin-guide-cgroup-v1-memoryrst-dont-reference-page_mapcount.patch