The patch titled
Subject: mm: memory-hotplug: check folio ref count first in do_migrate_range
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-memory-hotplug-check-folio-ref-count-first-in-do_migrate_range.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-hotplug-check-folio-ref-count-first-in-do_migrate_range.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
Subject: mm: memory-hotplug: check folio ref count first in do_migrate_range
Date: Mon, 17 Feb 2025 09:43:28 +0800
If a folio has an increased reference count, folio_try_get() will acquire
it, perform necessary operations, and then release it. In the case of a
poisoned folio without an elevated reference count (which is unlikely for
memory-failure), folio_try_get() will simply bypass it.
Therefore, relocate the folio_try_get() function, responsible for checking
and acquiring this reference count at first.
Link: https://lkml.kernel.org/r/20250217014329.3610326-3-mawupeng1@xxxxxxxxxx
Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
--- a/mm/memory_hotplug.c~mm-memory-hotplug-check-folio-ref-count-first-in-do_migrate_range
+++ a/mm/memory_hotplug.c
@@ -1822,12 +1822,12 @@ static void do_migrate_range(unsigned lo
if (folio_test_large(folio))
pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1;
- /*
- * HWPoison pages have elevated reference counts so the migration would
- * fail on them. It also doesn't make any sense to migrate them in the
- * first place. Still try to unmap such a page in case it is still mapped
- * (keep the unmap as the catch all safety net).
- */
+ if (!folio_try_get(folio))
+ continue;
+
+ if (unlikely(page_folio(page) != folio))
+ goto put_folio;
+
if (folio_test_hwpoison(folio) ||
(folio_test_large(folio) && folio_test_has_hwpoisoned(folio))) {
if (WARN_ON(folio_test_lru(folio)))
@@ -1835,14 +1835,8 @@ static void do_migrate_range(unsigned lo
if (folio_mapped(folio))
unmap_poisoned_folio(folio, pfn, false);
- continue;
- }
-
- if (!folio_try_get(folio))
- continue;
-
- if (unlikely(page_folio(page) != folio))
goto put_folio;
+ }
if (!isolate_folio_to_list(folio, &source)) {
if (__ratelimit(&migrate_rs)) {
_
Patches currently in -mm which might be from mawupeng1@xxxxxxxxxx are
mm-memory-failure-update-ttu-flag-inside-unmap_poisoned_folio.patch
mm-memory-hotplug-check-folio-ref-count-first-in-do_migrate_range.patch
hwpoison-memory_hotplug-lock-folio-before-unmap-hwpoisoned-folio.patch
