block/loop: set hw_sectors

Loop can handle any size of request. Limiting it to 255 sectors just
burns the CPU for bio split and request merge for underlayer disk and
also cause bad fs block allocation in directio mode.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NShaohua Li <shli@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1736,6 +1736,7 @@ static int loop_add(struct loop_device **l, int i)
 
 	blk_queue_physical_block_size(lo->lo_queue, PAGE_SIZE);
 
+	blk_queue_max_hw_sectors(lo->lo_queue, BLK_DEF_MAX_SECTORS);
 	/*
 	 * It doesn't make sense to enable merge because the I/O
 	 * submitted to backing file is handled page by page.