xen-blkfront: set blk_queue_max_hw_sectors correctly

Now that indirect segments are enabled blk_queue_max_hw_sectors must
be set to match the maximum number of sectors we can handle in a
request.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reported-by: Felipe Franciosi <felipe.franciosi@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkfront.c

@@ -633,7 +633,7 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
 	/* Hard sector size and max sectors impersonate the equiv. hardware. */
 	blk_queue_logical_block_size(rq, sector_size);
 	blk_queue_physical_block_size(rq, physical_sector_size);
-	blk_queue_max_hw_sectors(rq, 512);
+	blk_queue_max_hw_sectors(rq, (segments * PAGE_SIZE) / 512);
 
 	/* Each segment in a request is up to an aligned page in size. */
 	blk_queue_segment_boundary(rq, PAGE_SIZE - 1);