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authorNaoya Horiguchi <naoya.horiguchi@nec.com>2022-07-14 13:24:13 +0900
committerAndrew Morton <akpm@linux-foundation.org>2022-08-08 18:06:43 -0700
commitc0531714d6e3fd720b7dacc2de2d0503a995bcdc (patch)
tree2eb6bcba208d42e396e402dee9ccd7b167938965 /mm
parente38f055d6d9a060dbf3f69fbac5b3b04a1566a56 (diff)
mm/hugetlb: check gigantic_page_runtime_supported() in return_unused_surplus_pages()
Patch series "mm, hwpoison: enable 1GB hugepage support", v7. 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/20220714042420.1847125-1-naoya.horiguchi@linux.dev Link: https://lkml.kernel.org/r/20220714042420.1847125-2-naoya.horiguchi@linux.dev Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Liu Shixin <liushixin2@huawei.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Muchun Song <songmuchun@bytedance.com> Cc: kernel test robot <lkp@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/hugetlb.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 598c37279fee..ee6655e47213 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(struct hstate *h,
/* 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;
/*