diff -Nur linux-2.6.32.orig/drivers/ata/libata-scsi.c linux-2.6.32/drivers/ata/libata-scsi.c
--- linux-2.6.32.orig/drivers/ata/libata-scsi.c	2009-12-03 14:51:21.000000000 +1100
+++ linux-2.6.32/drivers/ata/libata-scsi.c	2011-01-22 20:32:53.353775375 +1100
@@ -1099,13 +1099,13 @@
 	/* configure max sectors */
 	blk_queue_max_sectors(sdev->request_queue, dev->max_sectors);
 
+	sdev->sector_size = ATA_SECT_SIZE;
+
 	if (dev->class == ATA_DEV_ATAPI) {
 		struct request_queue *q = sdev->request_queue;
 		void *buf;
 
-		/* set the min alignment and padding */
-		blk_queue_update_dma_alignment(sdev->request_queue,
-					       ATA_DMA_PAD_SZ - 1);
+		/* set DMA padding */
 		blk_queue_update_dma_pad(sdev->request_queue,
 					 ATA_DMA_PAD_SZ - 1);
 
@@ -1119,12 +1119,24 @@
 
 		blk_queue_dma_drain(q, atapi_drain_needed, buf, ATAPI_MAX_DRAIN);
 	} else {
-		/* ATA devices must be sector aligned */
-		blk_queue_update_dma_alignment(sdev->request_queue,
-					       ATA_SECT_SIZE - 1);
 		sdev->manage_start_stop = 1;
 	}
 
+	/*
+	 * ata_pio_sectors() expects buffer for each sector to not cross
+	 * page boundary.  Enforce it by requiring buffers to be sector
+	 * aligned, which works iff sector_size is not larger than
+	 * PAGE_SIZE.  ATAPI devices also need the alignment as
+	 * IDENTIFY_PACKET is executed as ATA_PROT_PIO.
+	 */
+	if (sdev->sector_size > PAGE_SIZE)
+		ata_dev_printk(dev, KERN_WARNING,
+			"sector_size=%u > PAGE_SIZE, PIO may malfunction\n",
+			sdev->sector_size);
+
+	blk_queue_update_dma_alignment(sdev->request_queue,
+				       sdev->sector_size - 1);
+
 	if (dev->flags & ATA_DFLAG_AN)
 		set_bit(SDEV_EVT_MEDIA_CHANGE, sdev->supported_events);