[libata] increase max-sectors limit for modern drives

This is the much-discussed "speed up SATA" patch.  It limits requests
to 1MB as discussed, rather than the hardware maximum (32MB).

As soon as Jens Axboe's patch to dynamically determining request
size is merged, max_sectors becomes what it properly should be --
a description of the absolute hardware maximum.

drivers/scsi/libata-scsi.c

@@ -167,8 +167,27 @@ int ata_scsi_slave_config(struct scsi_device *sdev)
 {
 	sdev->use_10_for_rw = 1;
 	sdev->use_10_for_ms = 1;
+
 	blk_queue_max_phys_segments(sdev->request_queue, LIBATA_MAX_PRD);
 
+	if (sdev->id < ATA_MAX_DEVICES) {
+		struct ata_port *ap;
+		struct ata_device *dev;
+
+		ap = (struct ata_port *) &sdev->host->hostdata[0];
+		dev = &ap->device[sdev->id];
+
+		/* TODO: 1024 is an arbitrary number, not the
+		 * hardware maximum.  This should be increased to
+		 * 65534 when Jens Axboe's patch for dynamically
+		 * determining max_sectors is merged.
+		 */
+		if (dev->flags & ATA_DFLAG_LBA48) {
+			sdev->host->max_sectors = 2048;
+			blk_queue_max_sectors(sdev->request_queue, 2048);
+		}
+	}
+
 	return 0;	/* scsi layer doesn't check return value, sigh */
 }