ide: save the returned value of dma_map_sg

dma_map_sg could return a value different to 'nents' argument of
dma_map_sg so the ide stack needs to save it for the later usage
(e.g. for_each_sg).

The ide stack also needs to save the original sg_nents value for
pci_unmap_sg.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
[bart: backport to Linus' tree]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-dma.c

@@ -128,6 +128,7 @@ int ide_build_sglist(ide_drive_t *drive, struct request *rq)
 {
 	ide_hwif_t *hwif = drive->hwif;
 	struct scatterlist *sg = hwif->sg_table;
+	int i;
 
 	ide_map_sg(drive, rq);
 
@@ -136,8 +137,13 @@ int ide_build_sglist(ide_drive_t *drive, struct request *rq)
 	else
 		hwif->sg_dma_direction = DMA_TO_DEVICE;
 
-	return dma_map_sg(hwif->dev, sg, hwif->sg_nents,
-			  hwif->sg_dma_direction);
+	i = dma_map_sg(hwif->dev, sg, hwif->sg_nents, hwif->sg_dma_direction);
+	if (i) {
+		hwif->orig_sg_nents = hwif->sg_nents;
+		hwif->sg_nents = i;
+	}
+
+	return i;
 }
 EXPORT_SYMBOL_GPL(ide_build_sglist);
 
@@ -156,7 +162,7 @@ void ide_destroy_dmatable(ide_drive_t *drive)
 {
 	ide_hwif_t *hwif = drive->hwif;
 
-	dma_unmap_sg(hwif->dev, hwif->sg_table, hwif->sg_nents,
+	dma_unmap_sg(hwif->dev, hwif->sg_table, hwif->orig_sg_nents,
 		     hwif->sg_dma_direction);
 }
 EXPORT_SYMBOL_GPL(ide_destroy_dmatable);

include/linux/ide.h

@@ -797,6 +797,7 @@ typedef struct hwif_s {
 	struct scatterlist *sg_table;
 	int sg_max_nents;		/* Maximum number of entries in it */
 	int sg_nents;			/* Current number of entries in it */
+	int orig_sg_nents;
 	int sg_dma_direction;		/* dma transfer direction */
 
 	/* data phase of the active command (currently only valid for PIO/DMA) */