lkml.org 
[lkml]   [2019]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.2 114/162] Revert "dm bufio: fix deadlock with loop device"
    Date
    From: Mikulas Patocka <mpatocka@redhat.com>

    commit cf3591ef832915892f2499b7e54b51d4c578b28c upstream.

    Revert the commit bd293d071ffe65e645b4d8104f9d8fe15ea13862. The proper
    fix has been made available with commit d0a255e795ab ("loop: set
    PF_MEMALLOC_NOIO for the worker thread").

    Note that the fix offered by commit bd293d071ffe 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: Mikulas Patocka <mpatocka@redhat.com>
    Cc: stable@vger.kernel.org
    Fixes: bd293d071ffe ("dm bufio: fix deadlock with loop device")
    Depends-on: d0a255e795ab ("loop: set PF_MEMALLOC_NOIO for the worker thread")
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/md/dm-bufio.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/md/dm-bufio.c
    +++ b/drivers/md/dm-bufio.c
    @@ -1599,7 +1599,9 @@ dm_bufio_shrink_scan(struct shrinker *sh
    unsigned long freed;

    c = container_of(shrink, struct dm_bufio_client, shrinker);
    - if (!dm_bufio_trylock(c))
    + if (sc->gfp_mask & __GFP_FS)
    + dm_bufio_lock(c);
    + else if (!dm_bufio_trylock(c))
    return SHRINK_STOP;

    freed = __scan(c, sc->nr_to_scan, sc->gfp_mask);

    \
     
     \ /
      Last update: 2019-08-27 10:09    [W:3.078 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site