scsi: scatter gather alignment constraints

Make sg and st respect any block alignment
constraints for the data.  Usb storage already
sets these to what it needs.

Also reset the default to 7 for other SCSI devices.

drivers/scsi/scsi_lib.c

@@ -1284,6 +1284,15 @@ struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
 	blk_queue_max_sectors(q, shost->max_sectors);
 	blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
 	blk_queue_segment_boundary(q, shost->dma_boundary);
+ 
+	/*
+	 * Set the queue's mask to require a mere 8-byte alignment for
+	 * DMA buffers, rather than the default 512.  This shouldn't
+	 * inconvenience any user programs and should be okay for most
+	 * host adapters.  A host driver can alter this mask in its
+	 * slave_alloc() or slave_configure() callback if necessary.
+	 */
+	blk_queue_dma_alignment(q, (8 - 1));
 
 	if (!shost->use_clustering)
 		clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);

drivers/scsi/sg.c

@@ -1797,7 +1797,11 @@ sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len)
 	int sg_tablesize = sfp->parentdp->sg_tablesize;
 	struct scatterlist *sgl;
 	int mx_sc_elems, res;
+	struct scsi_device *sdev = sfp->parentdp->device;
 
+	if (((unsigned long)hp->dxferp &
+			queue_dma_alignment(sdev->request_queue)) != 0)
+		return 1;
 	mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
         if (mx_sc_elems <= 0) {
                 return 1;

drivers/scsi/st.c

@@ -1272,7 +1272,8 @@ static int setup_buffering(Scsi_Tape *STp, const char *buf, size_t count, int is
 		i = STp->try_dio && try_rdio;
 	else
 		i = STp->try_dio && try_wdio;
-	if (i) {
+	if (i && ((unsigned long)buf & queue_dma_alignment(
+					STp->device->request_queue)) == 0) {
 		i = st_map_user_pages(&(STbp->sg[0]), STbp->use_sg,
 				      (unsigned long)buf, count, (is_read ? READ : WRITE),
 				      STp->max_pfn);