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    Subject[PATCH 5.15 083/102] mm/huge_memory: do not overkill when splitting huge_zero_page
    Date
    From: Xu Yu <xuyu@linux.alibaba.com>

    commit 478d134e9506c7e9bfe2830ed03dd85e97966313 upstream.

    Kernel panic when injecting memory_failure for the global huge_zero_page,
    when CONFIG_DEBUG_VM is enabled, as follows.

    Injecting memory failure for pfn 0x109ff9 at process virtual address 0x20ff9000
    page:00000000fb053fc3 refcount:2 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x109e00
    head:00000000fb053fc3 order:9 compound_mapcount:0 compound_pincount:0
    flags: 0x17fffc000010001(locked|head|node=0|zone=2|lastcpupid=0x1ffff)
    raw: 017fffc000010001 0000000000000000 dead000000000122 0000000000000000
    raw: 0000000000000000 0000000000000000 00000002ffffffff 0000000000000000
    page dumped because: VM_BUG_ON_PAGE(is_huge_zero_page(head))
    ------------[ cut here ]------------
    kernel BUG at mm/huge_memory.c:2499!
    invalid opcode: 0000 [#1] PREEMPT SMP PTI
    CPU: 6 PID: 553 Comm: split_bug Not tainted 5.18.0-rc1+ #11
    Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 3288b3c 04/01/2014
    RIP: 0010:split_huge_page_to_list+0x66a/0x880
    Code: 84 9b fb ff ff 48 8b 7c 24 08 31 f6 e8 9f 5d 2a 00 b8 b8 02 00 00 e9 e8 fb ff ff 48 c7 c6 e8 47 3c 82 4c b
    RSP: 0018:ffffc90000dcbdf8 EFLAGS: 00010246
    RAX: 000000000000003c RBX: 0000000000000001 RCX: 0000000000000000
    RDX: 0000000000000000 RSI: ffffffff823e4c4f RDI: 00000000ffffffff
    RBP: ffff88843fffdb40 R08: 0000000000000000 R09: 00000000fffeffff
    R10: ffffc90000dcbc48 R11: ffffffff82d68448 R12: ffffea0004278000
    R13: ffffffff823c6203 R14: 0000000000109ff9 R15: ffffea000427fe40
    FS: 00007fc375a26740(0000) GS:ffff88842fd80000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007fc3757c9290 CR3: 0000000102174006 CR4: 00000000003706e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    try_to_split_thp_page+0x3a/0x130
    memory_failure+0x128/0x800
    madvise_inject_error.cold+0x8b/0xa1
    __x64_sys_madvise+0x54/0x60
    do_syscall_64+0x35/0x80
    entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x7fc3754f8bf9
    Code: 01 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 8
    RSP: 002b:00007ffeda93a1d8 EFLAGS: 00000217 ORIG_RAX: 000000000000001c
    RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc3754f8bf9
    RDX: 0000000000000064 RSI: 0000000000003000 RDI: 0000000020ff9000
    RBP: 00007ffeda93a200 R08: 0000000000000000 R09: 0000000000000000
    R10: 00000000ffffffff R11: 0000000000000217 R12: 0000000000400490
    R13: 00007ffeda93a2e0 R14: 0000000000000000 R15: 0000000000000000

    We think that raising BUG is overkilling for splitting huge_zero_page, the
    huge_zero_page can't be met from normal paths other than memory failure,
    but memory failure is a valid caller. So we tend to replace the BUG to
    WARN + returning -EBUSY, and thus the panic above won't happen again.

    Link: https://lkml.kernel.org/r/f35f8b97377d5d3ede1bc5ac3114da888c57cbce.1651052574.git.xuyu@linux.alibaba.com
    Fixes: d173d5417fb6 ("mm/memory-failure.c: skip huge_zero_page in memory_failure()")
    Fixes: 6a46079cf57a ("HWPOISON: The high level memory error handler in the VM v7")
    Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
    Suggested-by: Yang Shi <shy828301@gmail.com>
    Reported-by: kernel test robot <lkp@intel.com>
    Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
    Reviewed-by: Yang Shi <shy828301@gmail.com>
    Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    mm/huge_memory.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/mm/huge_memory.c
    +++ b/mm/huge_memory.c
    @@ -2617,11 +2617,16 @@ int split_huge_page_to_list(struct page
    struct address_space *mapping = NULL;
    int extra_pins, ret;
    pgoff_t end;
    + bool is_hzp;

    - VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
    VM_BUG_ON_PAGE(!PageLocked(head), head);
    VM_BUG_ON_PAGE(!PageCompound(head), head);

    + is_hzp = is_huge_zero_page(head);
    + VM_WARN_ON_ONCE_PAGE(is_hzp, head);
    + if (is_hzp)
    + return -EBUSY;
    +
    if (PageWriteback(head))
    return -EBUSY;


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