• Tejun Heo's avatar
    libata: convert to chained sg · ff2aeb1e
    Tejun Heo authored
    
    
    libata used private sg iterator to handle padding sg.  Now that sg can
    be chained, padding can be handled using standard sg ops.  Convert to
    chained sg.
    
    * s/qc->__sg/qc->sg/
    
    * s/qc->pad_sgent/qc->extra_sg[]/.  Because chaining consumes one sg
      entry.  There need to be two extra sg entries.  The renaming is also
      for future addition of other extra sg entries.
    
    * Padding setup is moved into ata_sg_setup_extra() which is organized
      in a way that future addition of other extra sg entries is easy.
    
    * qc->orig_n_elem is unused and removed.
    
    * qc->n_elem now contains the number of sg entries that LLDs should
      map.  qc->mapped_n_elem is added to carry the original number of
      mapped sgs for unmapping.
    
    * The last sg of the original sg list is used to chain to extra sg
      list.  The original last sg is pointed to by qc->last_sg and the
      content is stored in qc->saved_last_sg.  It's restored during
      ata_sg_clean().
    
    * All sg walking code has been updated.  Unnecessary assertions and
      checks for conditions the core layer already guarantees are removed.
    Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
    Cc: Jens Axboe <jens.axboe@oracle.com>
    Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
    ff2aeb1e
ahci.c 62 KB