• H. Peter Anvin's avatar
    md/raid1,5,10: Disable WRITE SAME until a recovery strategy is in place · 5026d7a9
    H. Peter Anvin authored
    There are cases where the kernel will believe that the WRITE SAME
    command is supported by a block device which does not, in fact,
    support WRITE SAME.  This currently happens for SATA drivers behind a
    SAS controller, but there are probably a hundred other ways that can
    happen, including drive firmware bugs.
    
    After receiving an error for WRITE SAME the block layer will retry the
    request as a plain write of zeroes, but mdraid will consider the
    failure as fatal and consider the drive failed.  This has the effect
    that all the mirrors containing a specific set of data are each
    offlined in very rapid succession resulting in data loss.
    
    However, just bouncing the request back up to the block layer isn't
    ideal either, because the whole initial request-retry sequence should
    be inside the write bitmap fence, which probably means that md needs
    to do its own conversion of WRITE SAME to write zero.
    
    Until the failure scenario has been sorted out, disable WRITE SAME for
    raid1, raid5, and raid10.
    
    [neilb: added raid5]
    
    This patch is appropriate for any -stable since 3.7 when write_same
    support was added.
    
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    Signed-off-by: default avatarNeilBrown <neilb@suse.de>
    5026d7a9
raid1.c 84.2 KB