sd: Block limits VPD support

Query the block limits VPD page and adjust queue minimum and optimal I/O
sizes.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/sd.c

@@ -1794,6 +1794,29 @@ void sd_read_app_tag_own(struct scsi_disk *sdkp, unsigned char *buffer)
 	return;
 }
 
+/**
+ * sd_read_block_limits - Query disk device for preferred I/O sizes.
+ * @disk: disk to query
+ */
+static void sd_read_block_limits(struct scsi_disk *sdkp)
+{
+	unsigned int sector_sz = sdkp->device->sector_size;
+	char *buffer;
+
+	/* Block Limits VPD */
+	buffer = scsi_get_vpd_page(sdkp->device, 0xb0);
+
+	if (buffer == NULL)
+		return;
+
+	blk_queue_io_min(sdkp->disk->queue,
+			 get_unaligned_be16(&buffer[6]) * sector_sz);
+	blk_queue_io_opt(sdkp->disk->queue,
+			 get_unaligned_be32(&buffer[12]) * sector_sz);
+
+	kfree(buffer);
+}
+
 /**
  * sd_read_block_characteristics - Query block dev. characteristics
  * @disk: disk to query
@@ -1854,6 +1877,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
 	 */
 	if (sdkp->media_present) {
 		sd_read_capacity(sdkp, buffer);
+		sd_read_block_limits(sdkp);
 		sd_read_block_characteristics(sdkp);
 		sd_read_write_protect_flag(sdkp, buffer);
 		sd_read_cache_type(sdkp, buffer);