The patch titled
Subject: mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()
has been added to the -mm mm-unstable branch. Its filename is
mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.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: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()
Date: Fri, 8 Jul 2022 14:36:46 +0900
Patch series "mm, hwpoison: enable 1GB hugepage support", v5.
This patch (of 8):
I found a weird state of 1GB hugepage pool, caused by the following
procedure:
- run a process reserving all free 1GB hugepages,
- shrink free 1GB hugepage pool to zero (i.e. writing 0 to
/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then
- kill the reserving process.
, then all the hugepages are free *and* surplus at the same time.
$ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
3
$ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages
3
$ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages
0
$ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages
3
This state is resolved by reserving and allocating the pages then freeing
them again, so this seems not to result in serious problem. But it's a
little surprising (shrinking pool suddenly fails).
This behavior is caused by hstate_is_gigantic() check in
return_unused_surplus_pages(). This was introduced so long ago in 2008 by
commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and at
that time the gigantic pages were not supposed to be allocated/freed at
run-time. Now kernel can support runtime allocation/free, so let's check
gigantic_page_runtime_supported() together.
Link: https://lkml.kernel.org/r/20220708053653.964464-1-naoya.horiguchi@xxxxxxxxx
Link: https://lkml.kernel.org/r/20220708053653.964464-2-naoya.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages
+++ a/mm/hugetlb.c
@@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(
/* Uncommit the reservation */
h->resv_huge_pages -= unused_resv_pages;
- /* Cannot return gigantic pages currently */
- if (hstate_is_gigantic(h))
+ if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
goto out;
/*
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mm-hugetlb-separate-path-for-hwpoison-entry-in-copy_hugetlb_page_range.patch
mm-hugetlb-check-gigantic_page_runtime_supported-in-return_unused_surplus_pages.patch
mm-hugetlb-make-pud_huge-and-follow_huge_pud-aware-of-non-present-pud-entry.patch
mm-hwpoison-hugetlb-support-saving-mechanism-of-raw-error-pages.patch
mm-hwpoison-make-unpoison-aware-of-raw-error-info-in-hwpoisoned-hugepage.patch
mm-hwpoison-set-pg_hwpoison-for-busy-hugetlb-pages.patch
mm-hwpoison-make-__page_handle_poison-returns-int.patch
mm-hwpoison-skip-raw-hwpoison-page-in-freeing-1gb-hugepage.patch
mm-hwpoison-enable-memory-error-handling-on-1gb-hugepage.patch
