• Roman Gushchin's avatar
    md/raid5: fix locking in handle_stripe_clean_event() · b8a9d66d
    Roman Gushchin authored
    After commit 566c09c5 ("raid5: relieve lock contention in get_active_stripe()")
    __find_stripe() is called under conf->hash_locks + hash.
    But handle_stripe_clean_event() calls remove_hash() under
    conf->device_lock.
    
    Under some cirscumstances the hash chain can be circuited,
    and we get an infinite loop with disabled interrupts and locked hash
    lock in __find_stripe(). This leads to hard lockup on multiple CPUs
    and following system crash.
    
    I was able to reproduce this behavior on raid6 over 6 ssd disks.
    The devices_handle_discard_safely option should be set to enable trim
    support. The following script was used:
    
    for i in `seq 1 32`; do
        dd if=/dev/zero of=large$i bs=10M count=100 &
    done
    
    neilb: original was against a 3.x kernel.  I forward-ported
      to 4.3-rc.  This verison is suitable for any kernel since
      Commit: 59fc630b ("RAID5: batch adjacent full stripe write")
      (v4.1+).  I'll post a version for earlier kernels to stable.
    Signed-off-by: default avatarRoman Gushchin <klamm@yandex-team.ru>
    Fixes: 566c09c5 ("raid5: relieve lock contention in get_active_stripe()")
    Signed-off-by: default avatarNeilBrown <neilb@suse.com>
    Cc: Shaohua Li <shli@kernel.org>
    Cc: <stable@vger.kernel.org> # 3.13 - 4.2
    b8a9d66d
raid5.c 221 KB