The patch titled
Subject: mm/migrate: convert do_pages_stat_array() from follow_page() to folio_walk
has been added to the -mm mm-unstable branch. Its filename is
mm-migrate-convert-do_pages_stat_array-from-follow_page-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-migrate-convert-do_pages_stat_array-from-follow_page-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/migrate: convert do_pages_stat_array() from follow_page() to folio_walk
Date: Fri, 2 Aug 2024 17:55:16 +0200
Let's use folio_walk instead, so we can avoid taking a folio reference
just to read the nid and get rid of another follow_page()/FOLL_DUMP user.
Use FW_ZEROPAGE so we can return "-EFAULT" for it as documented.
The possible return values for follow_page() were confusing, especially
with FOLL_DUMP set. We'll handle it like documented in the man page:
* -EFAULT: This is a zero page or the memory area is not mapped by the
process.
* -ENOENT: The page is not present.
We'll keep setting -ENOENT for ZONE_DEVICE. Maybe not the right thing to
do, but it likely doesn't really matter (just like for weird devmap,
whereby we fake "not present").
Note that the other errors (-EACCESS, -EBUSY, -EIO, -EINVAL, -ENOMEM) so
far only applied when actually moving pages, not when only querying stats.
We'll effectively drop the "secretmem" check we had in follow_page(), but
that shouldn't really matter here, we're not accessing folio/page content
after all.
Link: https://lkml.kernel.org/r/20240802155524.517137-4-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/migrate.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
--- a/mm/migrate.c~mm-migrate-convert-do_pages_stat_array-from-follow_page-to-folio_walk
+++ a/mm/migrate.c
@@ -50,6 +50,7 @@
#include <linux/random.h>
#include <linux/sched/sysctl.h>
#include <linux/memory-tiers.h>
+#include <linux/pagewalk.h>
#include <asm/tlbflush.h>
@@ -2331,28 +2332,26 @@ static void do_pages_stat_array(struct m
for (i = 0; i < nr_pages; i++) {
unsigned long addr = (unsigned long)(*pages);
struct vm_area_struct *vma;
- struct page *page;
+ struct folio_walk fw;
+ struct folio *folio;
int err = -EFAULT;
vma = vma_lookup(mm, addr);
if (!vma)
goto set_status;
- /* FOLL_DUMP to ignore special (like zero) pages */
- page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
-
- err = PTR_ERR(page);
- if (IS_ERR(page))
- goto set_status;
-
- err = -ENOENT;
- if (!page)
- goto set_status;
-
- if (!is_zone_device_page(page))
- err = page_to_nid(page);
-
- put_page(page);
+ folio = folio_walk_start(&fw, vma, addr, FW_ZEROPAGE);
+ if (folio) {
+ if (is_zero_folio(folio) || is_huge_zero_folio(folio))
+ err = -EFAULT;
+ else if (folio_is_zone_device(folio))
+ err = -ENOENT;
+ else
+ err = folio_nid(folio);
+ folio_walk_end(&fw, vma);
+ } else {
+ err = -ENOENT;
+ }
set_status:
*status = err;
_
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
