The patch titled
Subject: hugetlb: fix update_and_free_page contig page struct assumption
has been added to the -mm tree. Its filename is
hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch
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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: hugetlb: fix update_and_free_page contig page struct assumption
page structs are not guaranteed to be contiguous for gigantic pages. The
routine update_and_free_page can encounter a gigantic page, yet it assumes
page structs are contiguous when setting page flags in subpages.
If update_and_free_page encounters non-contiguous page structs, we can see
“BUG: Bad page state in process …” errors.
Non-contiguous page structs are generally not an issue. However, they can
exist with a specific kernel configuration and hotplug operations. For
example: Configure the kernel with CONFIG_SPARSEMEM and
!CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where
the gigantic page will be allocated. Zi Yan outlined steps to reproduce
here [1].
[1] https://lore.kernel.org/linux-mm/16F7C58B-4D79-41C5-9B64-A1A1628F4AF2@xxxxxxxxxx/
Link: https://lkml.kernel.org/r/20210217184926.33567-1-mike.kravetz@xxxxxxxxxx
Fixes: 944d9fec8d7a ("hugetlb: add support for gigantic page allocation at runtime")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Joao Martins <joao.m.martins@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/hugetlb.c~hugetlb-fix-update_and_free_page-contig-page-struct-assumption
+++ a/mm/hugetlb.c
@@ -1321,14 +1321,16 @@ static inline void destroy_compound_giga
static void update_and_free_page(struct hstate *h, struct page *page)
{
int i;
+ struct page *subpage = page;
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
return;
h->nr_huge_pages--;
h->nr_huge_pages_node[page_to_nid(page)]--;
- for (i = 0; i < pages_per_huge_page(h); i++) {
- page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
+ for (i = 0; i < pages_per_huge_page(h);
+ i++, subpage = mem_map_next(subpage, page, i)) {
+ subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
1 << PG_referenced | 1 << PG_dirty |
1 << PG_active | 1 << PG_private |
1 << PG_writeback);
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
hugetlb-fix-update_and_free_page-contig-page-struct-assumption.patch
hugetlb-fix-copy_huge_page_from_user-contig-page-struct-assumption.patch
hugetlb-use-pageprivate-for-hugetlb-specific-page-flags.patch
hugetlb-convert-page_huge_active-hpagemigratable-flag.patch
hugetlb-convert-pagehugetemporary-to-hpagetemporary-flag.patch
hugetlb-convert-pagehugefreed-to-hpagefreed-flag.patch
mm-hugetlb-change-hugetlb_reserve_pages-to-type-bool.patch
hugetlbfs-remove-special-hugetlbfs_set_page_dirty.patch
