Add serial number support for virtio_blk, V4a

This patch extracts the opaque data from pci i/o
region 0 via the added VIRTIO_BLK_F_IDENTIFY
field.  By convention this data takes the form of
that returned by an ATA IDENTIFY DEVICE command,
however the driver (except for structure size)
makes no interpretation of the data.  The structure
data is copied wholesale to userspace via a
HDIO_GET_IDENTITY ioctl command (eg: hdparm -i <dev>).

Signed-off-by: john cooper <john.cooper@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/block/virtio_blk.c

@@ -171,20 +171,51 @@ static void do_virtblk_request(struct request_queue *q)
 		vblk->vq->vq_ops->kick(vblk->vq);
 }
 
+/* return ATA identify data
+ */
+static int virtblk_identify(struct gendisk *disk, void *argp)
+{
+	struct virtio_blk *vblk = disk->private_data;
+	void *opaque;
+	int err = -ENOMEM;
+
+	opaque = kmalloc(VIRTIO_BLK_ID_BYTES, GFP_KERNEL);
+	if (!opaque)
+		goto out;
+
+	err = virtio_config_buf(vblk->vdev, VIRTIO_BLK_F_IDENTIFY,
+		offsetof(struct virtio_blk_config, identify), opaque,
+		VIRTIO_BLK_ID_BYTES);
+
+	if (err)
+		goto out_kfree;
+
+	if (copy_to_user(argp, opaque, VIRTIO_BLK_ID_BYTES))
+		err = -EFAULT;
+
+out_kfree:
+	kfree(opaque);
+out:
+	return err;
+}
+
 static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
 			 unsigned cmd, unsigned long data)
 {
 	struct gendisk *disk = bdev->bd_disk;
 	struct virtio_blk *vblk = disk->private_data;
+	void __user *argp = (void __user *)data;
+
+	if (cmd == HDIO_GET_IDENTITY)
+		return virtblk_identify(disk, argp);
 
 	/*
 	 * Only allow the generic SCSI ioctls if the host can support it.
 	 */
 	if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
 		return -ENOIOCTLCMD;
 
-	return scsi_cmd_ioctl(disk->queue, disk, mode, cmd,
-			      (void __user *)data);
+	return scsi_cmd_ioctl(disk->queue, disk, mode, cmd, argp);
 }
 
 /* We provide getgeo only to please some old bootloader/partitioning tools */
@@ -390,7 +421,7 @@ static struct virtio_device_id id_table[] = {
 static unsigned int features[] = {
 	VIRTIO_BLK_F_BARRIER, VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX,
 	VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
-	VIRTIO_BLK_F_SCSI,
+	VIRTIO_BLK_F_SCSI, VIRTIO_BLK_F_IDENTIFY
 };
 
 static struct virtio_driver virtio_blk = {

include/linux/virtio_blk.h

@@ -16,6 +16,9 @@
 #define VIRTIO_BLK_F_RO		5	/* Disk is read-only */
 #define VIRTIO_BLK_F_BLK_SIZE	6	/* Block size of disk is available*/
 #define VIRTIO_BLK_F_SCSI	7	/* Supports scsi command passthru */
+#define VIRTIO_BLK_F_IDENTIFY	8	/* ATA IDENTIFY supported */
+
+#define VIRTIO_BLK_ID_BYTES	(sizeof(__u16[256]))	/* IDENTIFY DATA */
 
 struct virtio_blk_config
 {
@@ -33,6 +36,7 @@ struct virtio_blk_config
 	} geometry;
 	/* block size of device (if VIRTIO_BLK_F_BLK_SIZE) */
 	__u32 blk_size;
+	__u8 identify[VIRTIO_BLK_ID_BYTES];
 } __attribute__((packed));
 
 /* These two define direction. */