• Mikulas Patocka's avatar
    Revert "dm bufio: fix deadlock with loop device" · cf3591ef
    Mikulas Patocka authored
    Revert the commit bd293d07. The proper
    fix has been made available with commit d0a255e7 ("loop: set
    PF_MEMALLOC_NOIO for the worker thread").
    
    Note that the fix offered by commit bd293d07 doesn't really prevent
    the deadlock from occuring - if we look at the stacktrace reported by
    Junxiao Bi, we see that it hangs in bit_wait_io and not on the mutex -
    i.e. it has already successfully taken the mutex. Changing the mutex
    from mutex_lock to mutex_trylock won't help with deadlocks that happen
    afterwards.
    
    PID: 474    TASK: ffff8813e11f4600  CPU: 10  COMMAND: "kswapd0"
       #0 [ffff8813dedfb938] __schedule at ffffffff8173f405
       #1 [ffff8813dedfb990] schedule at ffffffff8173fa27
       #2 [ffff8813dedfb9b0] schedule_timeout at ffffffff81742fec
       #3 [ffff8813dedfba60] io_schedule_timeout at ffffffff8173f186
       #4 [ffff8813dedfbaa0] bit_wait_io at ffffffff8174034f
       #5 [ffff8813dedfbac0] __wait_on_bit at ffffffff8173fec8
       #6 [ffff8813dedfbb10] out_of_line_wait_on_bit at ffffffff8173ff81
       #7 [ffff8813dedfbb90] __make_buffer_clean at ffffffffa038736f [dm_bufio]
       #8 [ffff8813dedfbbb0] __try_evict_buffer at ffffffffa0387bb8 [dm_bufio]
       #9 [ffff8813dedfbbd0] dm_bufio_shrink_scan at ffffffffa0387cc3 [dm_bufio]
      #10 [ffff8813dedfbc40] shrink_slab at ffffffff811a87ce
      #11 [ffff8813dedfbd30] shrink_zone at ffffffff811ad778
      #12 [ffff8813dedfbdc0] kswapd at ffffffff811ae92f
      #13 [ffff8813dedfbec0] kthread at ffffffff810a8428
      #14 [ffff8813dedfbf50] ret_from_fork at ffffffff81745242
    Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Cc: stable@vger.kernel.org
    Fixes: bd293d07 ("dm bufio: fix deadlock with loop device")
    Depends-on: d0a255e7 ("loop: set PF_MEMALLOC_NOIO for the worker thread")
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    cf3591ef
dm-bufio.c 47.8 KB