• Tejun Heo's avatar
    libata: revert convert-to-block-tagging patches · 8a8bc223
    Tejun Heo authored
    This patch reverts the following three commits which convert libata to
    use block layer tagging.
    
     43a49cbd
     e013e13b
     2fca5ccf
    
    Although using block layer tagging is the right direction, due to the
    tight coupling among tag number, data structure allocation and
    hardware command slot allocation, libata doesn't work correctly with
    the current conversion.
    
    The biggest problem is guaranteeing that tag 0 is always used for
    non-NCQ commands.  Due to the way blk-tag is implemented and how SCSI
    starts and finishes requests, such guarantee can't be made.  I'm not
    sure whether this would actually break any low level driver but it
    doesn't look like a good idea to break such assumption given the
    frailty of ATA controllers.
    
    So, for the time being, keep using the old dumb in-libata qc
    allocation.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Cc: Jens Axobe <jens.axboe@oracle.com>
    Cc: Jeff Garzik <jeff@garzik.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8a8bc223
libata-scsi.c 93.4 KB