Index: ata-dma.c
===================================================================
RCS file: /home/source/dragonfly/cvs/src/sys/dev/disk/nata/ata-dma.c,v
retrieving revision 1.4
diff -u -p -r1.4 ata-dma.c
--- ata-dma.c	5 Jun 2007 18:30:40 -0000	1.4
+++ ata-dma.c	18 Jul 2007 06:53:51 -0000
@@ -75,7 +75,7 @@ ata_dmainit(device_t dev)
     ch->dma->alignment = 2;
     ch->dma->boundary = 128 * DEV_BSIZE;
     ch->dma->segsize = 128 * DEV_BSIZE;
-    ch->dma->max_iosize = 128 * DEV_BSIZE;
+    ch->dma->max_iosize = 64 * DEV_BSIZE;
     ch->dma->max_address = BUS_SPACE_MAXADDR_32BIT;
 }
 
@@ -213,6 +213,7 @@ ata_dmasetprd(void *xsc, bus_dma_segment
     args->nsegs = nsegs;
 }
 
+void db_print_backtrace(void);
 static int
 ata_dmaload(device_t dev, caddr_t data, int32_t count, int dir,
 	    void *addr, int *entries)
@@ -237,6 +238,7 @@ ata_dmaload(device_t dev, caddr_t data, 
     if (count > ch->dma->max_iosize) {
 	device_printf(dev, "FAILURE - oversized DMA transfer attempt %d > %d\n",
 		      count, ch->dma->max_iosize);
+	db_print_backtrace();
 	return EIO;
     }