sd: Disable support for 256 byte/sector disks

commit 74856fbf upstream.

256 bytes per sector support has been broken since 2.6.X,
and no-one stepped up to fix this.
So disable support for it.
Signed-off-by: Mark Hounschell <dmarkh@cfl.rr.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/scsi/sd.c

@@ -1338,6 +1338,7 @@ static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
 {
 	u64 start_lba = blk_rq_pos(scmd->request);
 	u64 end_lba = blk_rq_pos(scmd->request) + (scsi_bufflen(scmd) / 512);
+	u64 factor = scmd->device->sector_size / 512;
 	u64 bad_lba;
 	int info_valid;
 	/*
@@ -1359,16 +1360,9 @@ static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
 	if (scsi_bufflen(scmd) <= scmd->device->sector_size)
 		return 0;
 
-	if (scmd->device->sector_size < 512) {
-		/* only legitimate sector_size here is 256 */
-		start_lba <<= 1;
-		end_lba <<= 1;
-	} else {
-		/* be careful ... don't want any overflows */
-		u64 factor = scmd->device->sector_size / 512;
-		do_div(start_lba, factor);
-		do_div(end_lba, factor);
-	}
+	/* be careful ... don't want any overflows */
+	do_div(start_lba, factor);
+	do_div(end_lba, factor);
 
 	/* The bad lba was reported incorrectly, we have no idea where
 	 * the error is.
@@ -1895,8 +1889,7 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
 	if (sector_size != 512 &&
 	    sector_size != 1024 &&
 	    sector_size != 2048 &&
-	    sector_size != 4096 &&
-	    sector_size != 256) {
+	    sector_size != 4096) {
 		sd_printk(KERN_NOTICE, sdkp, "Unsupported sector size %d.\n",
 			  sector_size);
 		/*
@@ -1945,8 +1938,6 @@ sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer)
 		sdkp->capacity <<= 2;
 	else if (sector_size == 1024)
 		sdkp->capacity <<= 1;
-	else if (sector_size == 256)
-		sdkp->capacity >>= 1;
 
 	blk_queue_physical_block_size(sdp->request_queue,
 				      sdkp->physical_block_size);