The patch titled Subject: mm: hwpoison: fix thp split handing in soft_offline_in_use_page() has been added to the -mm tree. Its filename is mm-hwpoison-fix-thp-split-handing-in-soft_offline_in_use_page.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-hwpoison-fix-thp-split-handing-i... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-hwpoison-fix-thp-split-handing-i...

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------------------------------------------------------ From: zhongjiang zhongjiang@huawei.com Subject: mm: hwpoison: fix thp split handing in soft_offline_in_use_page()

When soft_offline_in_use_page() runs on a thp tail page after pmd is split, we trigger the following VM_BUG_ON_PAGE():

Memory failure: 0x3755ff: non anonymous thp __get_any_page: 0x3755ff: unknown zero refcount page type 2fffff80000000 Soft offlining pfn 0x34d805 at process virtual address 0x20fff000 page:ffffea000d360140 count:0 mapcount:0 mapping:0000000000000000 index:0x1 flags: 0x2fffff80000000() raw: 002fffff80000000 ffffea000d360108 ffffea000d360188 0000000000000000 raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0) ------------[ cut here ]------------ kernel BUG at ./include/linux/mm.h:519!

soft_offline_in_use_page() passed refcount and page lock from tail page to head page, which is not needed because we can pass any subpage to split_huge_page().

Naoya had fixed a similar issue in c3901e722b29 ("mm: hwpoison: fix thp split handling in memory_failure()"). But he missed fixing soft offline.

Link: http://lkml.kernel.org/r/1551452476-24000-1-git-send-email-zhongjiang@huawei... Fixes: 61f5d698cc97 ("mm: re-enable THP") Signed-off-by: zhongjiang zhongjiang@huawei.com Acked-by: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Michal Hocko mhocko@suse.com Cc: Hugh Dickins hughd@google.com Cc: Kirill A. Shutemov kirill@shutemov.name Cc: Andrea Arcangeli aarcange@redhat.com Cc: stable@vger.kernel.org [4.5+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/memory-failure.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)

--- a/mm/memory-failure.c~mm-hwpoison-fix-thp-split-handing-in-soft_offline_in_use_page +++ a/mm/memory-failure.c @@ -1825,19 +1825,17 @@ static int soft_offline_in_use_page(stru struct page *hpage = compound_head(page);

if (!PageHuge(page) && PageTransHuge(hpage)) { - lock_page(hpage); - if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) { - unlock_page(hpage); - if (!PageAnon(hpage)) + lock_page(page); + if (!PageAnon(page) || unlikely(split_huge_page(page))) { + unlock_page(page); + if (!PageAnon(page)) pr_info("soft offline: %#lx: non anonymous thp\n", page_to_pfn(page)); else pr_info("soft offline: %#lx: thp split failed\n", page_to_pfn(page)); - put_hwpoison_page(hpage); + put_hwpoison_page(page); return -EBUSY; } - unlock_page(hpage); - get_hwpoison_page(page); - put_hwpoison_page(hpage); + unlock_page(page); }

/* _

Patches currently in -mm which might be from zhongjiang@huawei.com are

mm-hwpoison-fix-thp-split-handing-in-soft_offline_in_use_page.patch