Re-shuffle the code to be more efficient by not initializing variables
upfront (i.e. do it only when necessary). Also replace the do_div calls
with calls to sectors_to_logical().
No functional change is introduced by this patch.
[mkp: bytes_to_logical()]
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>