scsi: simplify scsi_bios_ptable

Use read_mapping_page and kmemdup instead of the odd read_dev_sector and
put_dev_sector helpers from the partitioning code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/scsi/scsicam.c

@@ -35,19 +35,17 @@ static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds
  */
 unsigned char *scsi_bios_ptable(struct block_device *dev)
 {
-	unsigned char *res = kmalloc(66, GFP_KERNEL);
-	if (res) {
-		struct block_device *bdev = dev->bd_contains;
-		Sector sect;
-		void *data = read_dev_sector(bdev, 0, &sect);
-		if (data) {
-			memcpy(res, data + 0x1be, 66);
-			put_dev_sector(sect);
-		} else {
-			kfree(res);
-			res = NULL;
-		}
-	}
+	struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;
+	unsigned char *res = NULL;
+	struct page *page;
+
+	page = read_mapping_page(mapping, 0, NULL);
+	if (IS_ERR(page))
+		return NULL;
+
+	if (!PageError(page))
+		res = kmemdup(page_address(page) + 0x1be, 66, GFP_KERNEL);
+	put_page(page);
 	return res;
 }
 EXPORT_SYMBOL(scsi_bios_ptable);