From: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Subject: mm: hwpoison: disable memory error handling on 1GB hugepage

Recently the following BUG was reported:

Injecting memory failure for pfn 0x3c0000 at process virtual address 0x7fe300000000 Memory failure: 0x3c0000: recovery action for huge page: Recovered BUG: unable to handle kernel paging request at ffff8dfcc0003000 IP: gup_pgd_range+0x1f0/0xc20 PGD 17ae72067 P4D 17ae72067 PUD 0 Oops: 0000 [#1] SMP PTI ... CPU: 3 PID: 5467 Comm: hugetlb_1gb Not tainted 4.15.0-rc8-mm1-abc+ #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014

You can easily reproduce this by calling madvise(MADV_HWPOISON) twice on a 1GB hugepage. This happens because get_user_pages_fast() is not aware of a migration entry on pud that was created in the 1st madvise() event.

I think that conversion to pud-aligned migration entry is working, but other MM code walking over page table isn't prepared for it. We need some time and effort to make all this work properly, so this patch avoids the reported bug by just disabling error handling for 1GB hugepage.

[n-horiguchi@ah.jp.nec.com: v2] Link: http://lkml.kernel.org/r/1517284444-18149-1-git-send-email-n-horiguchi@ah.jp... Link: http://lkml.kernel.org/r/1517207283-15769-1-git-send-email-n-horiguchi@ah.jp... Signed-off-by: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Acked-by: Michal Hocko mhocko@suse.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Punit Agrawal punit.agrawal@arm.com Tested-by: Michael Ellerman mpe@ellerman.id.au Cc: Anshuman Khandual khandual@linux.vnet.ibm.com Cc: "Aneesh Kumar K.V" aneesh.kumar@linux.vnet.ibm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

include/linux/mm.h | 1 + mm/memory-failure.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+)

diff -puN include/linux/mm.h~mm-hwpoison-disable-memory-error-handling-on-1gb-hugepage include/linux/mm.h --- a/include/linux/mm.h~mm-hwpoison-disable-memory-error-handling-on-1gb-hugepage +++ a/include/linux/mm.h @@ -2613,6 +2613,7 @@ enum mf_action_page_type { MF_MSG_POISONED_HUGE, MF_MSG_HUGE, MF_MSG_FREE_HUGE, + MF_MSG_NON_PMD_HUGE, MF_MSG_UNMAP_FAILED, MF_MSG_DIRTY_SWAPCACHE, MF_MSG_CLEAN_SWAPCACHE, diff -puN mm/memory-failure.c~mm-hwpoison-disable-memory-error-handling-on-1gb-hugepage mm/memory-failure.c --- a/mm/memory-failure.c~mm-hwpoison-disable-memory-error-handling-on-1gb-hugepage +++ a/mm/memory-failure.c @@ -502,6 +502,7 @@ static const char * const action_page_ty [MF_MSG_POISONED_HUGE] = "huge page already hardware poisoned", [MF_MSG_HUGE] = "huge page", [MF_MSG_FREE_HUGE] = "free huge page", + [MF_MSG_NON_PMD_HUGE] = "non-pmd-sized huge page", [MF_MSG_UNMAP_FAILED] = "unmapping failed page", [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page", [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page", @@ -1084,6 +1085,21 @@ static int memory_failure_hugetlb(unsign return 0; }

+ /* + * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so + * simply disable it. In order to make it work properly, we need + * make sure that: + * - conversion of a pud that maps an error hugetlb into hwpoison + * entry properly works, and + * - other mm code walking over page table is aware of pud-aligned + * hwpoison entries. + */ + if (huge_page_size(page_hstate(head)) > PMD_SIZE) { + action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED); + res = -EBUSY; + goto out; + } + if (!hwpoison_user_mappings(p, pfn, flags, &head)) { action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); res = -EBUSY; _