• Boaz Harrosh's avatar
    ore: Support for raid 6 · ce5d36aa
    Boaz Harrosh authored
    
    
    This simple patch adds support for raid6 to the ORE.
    Most operations and calculations where already for the general
    case. Only things left:
    * call async_gen_syndrome() in the case of raid6
      (NOTE that the raid6 math is the one supported by the Linux Kernel
       see: crypto/async_tx/async_pq.c)
    * call _ore_add_parity_unit() twice with only last call generating
      the redundancy pages.
    
    * Fix couple BUGS in old code
      a. In reads when parity==2 it can happen that per_dev->length=0
         but per_dev->offset was set and adjusted by _ore_add_sg_seg().
         Don't let it be overwritten.
      b. The all 'cur_comp > starting_dev' thing to determine if:
           "per_dev->offset is in the current stripe number or the
           next one."
         Was a complete raid5/4 accident. When parity==2 this is not
         at all true usually. All we need to do is increment si->ob_offset
         once we pass by the first parity device.
         (This also greatly simplifies the code, amen)
      c. Calculation of si->dev rotation can overflow when parity==2.
    
    * Then last enable raid6 in ore_verify_layout()
    
    I want to deeply thank Daniel Gryniewicz who found first all the
    bugs in the old raid code, and inspired these patches:
    	Inspired-by Daniel Gryniewicz <dang@linuxbox.com>
    
    Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
    ce5d36aa