• Jiang Biao's avatar
    virtio_balloon: fix another race between migration and ballooning · 89da619b
    Jiang Biao authored
    Kernel panic when with high memory pressure, calltrace looks like,
    PID: 21439 TASK: ffff881be3afedd0 CPU: 16 COMMAND: "java"
     #0 [ffff881ec7ed7630] machine_kexec at ffffffff81059beb
     #1 [ffff881ec7ed7690] __crash_kexec at ffffffff81105942
     #2 [ffff881ec7ed7760] crash_kexec at ffffffff81105a30
     #3 [ffff881ec7ed7778] oops_end at ffffffff816902c8
     #4 [ffff881ec7ed77a0] no_context at ffffffff8167ff46
     #5 [ffff881ec7ed77f0] __bad_area_nosemaphore at ffffffff8167ffdc
     #6 [ffff881ec7ed7838] __node_set at ffffffff81680300
     #7 [ffff881ec7ed7860] __do_page_fault at ffffffff8169320f
     #8 [ffff881ec7ed78c0] do_page_fault at ffffffff816932b5
     #9 [ffff881ec7ed78f0] page_fault at ffffffff8168f4c8
        [exception RIP: _raw_spin_lock_irqsave+47]
        RIP: ffffffff8168edef RSP: ffff881ec7ed79a8 RFLAGS: 00010046
        RAX: 0000000000000246 RBX: ffffea0019740d00 RCX: ffff881ec7ed7fd8
        RDX: 0000000000020000 RSI: 0000000000000016 RDI: 0000000000000008
        RBP: ffff881ec7ed79a8 R8: 0000000000000246 R9: 000000000001a098
        R10: ffff88107ffda000 R11: 0000000000000000 R12: 0000000000000000
        R13: 0000000000000008 R14: ffff881ec7ed7a80 R15: ffff881be3afedd0
        ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
    It happens in the pagefault and results in double pagefault
    during compacting pages when memory allocation fails.
    Analysed the vmcore, the page leads to second pagefault is corrupted
    with _mapcount=-256, but private=0.
    It's caused by the race between migration and ballooning, and lock
    missing in virtballoon_migratepage() of virtio_balloon driver.
    This patch fix the bug.
    Fixes: e2250429 ("virtio_balloon: introduce migration primitives to balloon pages")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarJiang Biao <jiang.biao2@zte.com.cn>
    Signed-off-by: default avatarHuang Chong <huang.chong@zte.com.cn>
    Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
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