The patch titled
Subject: mm/ksm: convert scan_get_next_rmap_item() from follow_page() to folio_walk
has been added to the -mm mm-unstable branch. Its filename is
mm-ksm-convert-scan_get_next_rmap_item-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-ksm-convert-scan_get_next_rmap_item-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/ksm: convert scan_get_next_rmap_item() from follow_page() to folio_walk
Date: Fri, 2 Aug 2024 17:55:19 +0200
Let's use folio_walk instead, for example avoiding taking temporary folio
references if the folio does obviously not even apply and getting rid of
one more follow_page() user. We cannot move all handling under the PTL,
so leave the rmap handling (which implies an allocation) out.
Note that zeropages obviously don't apply: old code could just have
specified FOLL_DUMP. Further, we don't care about losing the secretmem
check in follow_page(): these are never anon pages and
vma_ksm_compatible() would never consider secretmem vmas (VM_SHARED |
VM_MAYSHARE must be set for secretmem, see secretmem_mmap()).
Link: https://lkml.kernel.org/r/20240802155524.517137-7-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 | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)
--- a/mm/ksm.c~mm-ksm-convert-scan_get_next_rmap_item-from-follow_page-to-folio_walk
+++ a/mm/ksm.c
@@ -2564,36 +2564,46 @@ next_mm:
ksm_scan.address = vma->vm_end;
while (ksm_scan.address < vma->vm_end) {
+ struct page *tmp_page = NULL;
+ struct folio_walk fw;
+ struct folio *folio;
+
if (ksm_test_exit(mm))
break;
- *page = follow_page(vma, ksm_scan.address, FOLL_GET);
- if (IS_ERR_OR_NULL(*page)) {
- ksm_scan.address += PAGE_SIZE;
- cond_resched();
- continue;
+
+ folio = folio_walk_start(&fw, vma, ksm_scan.address, 0);
+ if (folio) {
+ if (!folio_is_zone_device(folio) &&
+ folio_test_anon(folio)) {
+ folio_get(folio);
+ tmp_page = fw.page;
+ }
+ folio_walk_end(&fw, vma);
}
- if (is_zone_device_page(*page))
- goto next_page;
- if (PageAnon(*page)) {
- flush_anon_page(vma, *page, ksm_scan.address);
- flush_dcache_page(*page);
+
+ if (tmp_page) {
+ flush_anon_page(vma, tmp_page, ksm_scan.address);
+ flush_dcache_page(tmp_page);
rmap_item = get_next_rmap_item(mm_slot,
ksm_scan.rmap_list, ksm_scan.address);
if (rmap_item) {
ksm_scan.rmap_list =
&rmap_item->rmap_list;
- if (should_skip_rmap_item(*page, rmap_item))
+ if (should_skip_rmap_item(tmp_page, rmap_item)) {
+ folio_put(folio);
goto next_page;
+ }
ksm_scan.address += PAGE_SIZE;
- } else
- put_page(*page);
+ *page = tmp_page;
+ } else {
+ folio_put(folio);
+ }
mmap_read_unlock(mm);
return rmap_item;
}
next_page:
- put_page(*page);
ksm_scan.address += PAGE_SIZE;
cond_resched();
}
_
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
