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...

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@huawei.com 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@huawei.com Signed-off-by: Ma Wupeng mawupeng1@huawei.com Cc: David Hildenbrand david@redhat.com Cc: Miaohe Lin linmiaohe@huawei.com Cc: Michal Hocko mhocko@suse.com Cc: Naoya Horiguchi nao.horiguchi@gmail.com Cc: Oscar Salvador osalvador@suse.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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@huawei.com 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