The patch titled
Subject: mm/damon: handle device-exclusive entries correctly in damon_folio_mkold_one()
has been added to the -mm mm-unstable branch. Its filename is
mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_mkold_one.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_mkold_one.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/damon: handle device-exclusive entries correctly in damon_folio_mkold_one()
Date: Mon, 10 Feb 2025 20:37:57 +0100
Ever since commit b756a3b5e7ea ("mm: device exclusive memory access") we
can return with a device-exclusive entry from page_vma_mapped_walk().
damon_folio_mkold_one() is not prepared for that and calls
damon_ptep_mkold() with PFN swap PTEs. Teach damon_ptep_mkold() to deal
with these PFN swap PTEs. Note that device-private entries are so far not
applicable on that path, as damon_get_folio() filters out non-lru folios.
Should we just skip PFN swap PTEs completely? Possible, but it seems
straight forward to just handle it correctly.
Note that we could currently only run into this case with device-exclusive
entries on THPs. We still adjust the mapcount on conversion to
device-exclusive; this makes the rmap walk abort early for small folios,
because we'll always have !folio_mapped() with a single device-exclusive
entry. We'll adjust the mapcount logic once all page_vma_mapped_walk()
users can properly handle device-exclusive entries.
Link: https://lkml.kernel.org/r/20250210193801.781278-16-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alex Shi <alexs@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Danilo Krummrich <dakr@xxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Karol Herbst <kherbst@xxxxxxxxxx>
Cc: Liam Howlett <liam.howlett@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Lyude <lyude@xxxxxxxxxx>
Cc: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Simona Vetter <simona.vetter@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Yanteng Si <si.yanteng@xxxxxxxxx>
Cc: Barry Song <v-songbaohua@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/ops-common.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
--- a/mm/damon/ops-common.c~mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_mkold_one
+++ a/mm/damon/ops-common.c
@@ -9,6 +9,8 @@
#include <linux/page_idle.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
#include "ops-common.h"
@@ -39,12 +41,29 @@ struct folio *damon_get_folio(unsigned l
void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr)
{
- struct folio *folio = damon_get_folio(pte_pfn(ptep_get(pte)));
+ pte_t pteval = ptep_get(pte);
+ struct folio *folio;
+ bool young = false;
+ unsigned long pfn;
+
+ if (likely(pte_present(pteval)))
+ pfn = pte_pfn(pteval);
+ else
+ pfn = swp_offset_pfn(pte_to_swp_entry(pteval));
+ folio = damon_get_folio(pfn);
if (!folio)
return;
- if (ptep_clear_young_notify(vma, addr, pte))
+ /*
+ * PFN swap PTEs, such as device-exclusive ones, that actually map pages
+ * are "old" from a CPU perspective. The MMU notifier takes care of any
+ * device aspects.
+ */
+ if (likely(pte_present(pteval)))
+ young |= ptep_test_and_clear_young(vma, addr, pte);
+ young |= mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE);
+ if (young)
folio_set_young(folio);
folio_set_idle(folio);
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-gup-reject-foll_split_pmd-with-hugetlb-vmas.patch
mm-rmap-reject-hugetlb-folios-in-folio_make_device_exclusive.patch
mm-rmap-convert-make_device_exclusive_range-to-make_device_exclusive.patch
mm-rmap-implement-make_device_exclusive-using-folio_walk-instead-of-rmap-walk.patch
mm-memory-detect-writability-in-restore_exclusive_pte-through-can_change_pte_writable.patch
mm-use-single-swp_device_exclusive-entry-type.patch
mm-page_vma_mapped-device-exclusive-entries-are-not-migration-entries.patch
kernel-events-uprobes-handle-device-exclusive-entries-correctly-in-__replace_page.patch
mm-ksm-handle-device-exclusive-entries-correctly-in-write_protect_page.patch
mm-rmap-handle-device-exclusive-entries-correctly-in-try_to_unmap_one.patch
mm-rmap-handle-device-exclusive-entries-correctly-in-try_to_migrate_one.patch
mm-rmap-handle-device-exclusive-entries-correctly-in-page_vma_mkclean_one.patch
mm-page_idle-handle-device-exclusive-entries-correctly-in-page_idle_clear_pte_refs_one.patch
mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_young_one.patch
mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_mkold_one.patch
mm-rmap-keep-mapcount-untouched-for-device-exclusive-entries.patch
mm-rmap-avoid-ebusy-from-make_device_exclusive.patch
