virtio_blk: provide getgeo

Rusty,

I currently try to make my guest boot from an virtio root device
without having an external kernel. Some of the tools that I tried
expect HDIO_GETGEO to work. The most interesting value is likely
the geo.start value to get the offset of a partition. This value
is filled by block/ioctl.c if fops->getgeo is set. This patch also
fills in some standard values for heads, sectors and cylinders.

Makes sense?

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6143337527e7..d2fe679519e4 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -152,9 +152,20 @@ static int virtblk_ioctl(struct inode *inode, struct file *filp,
                               (void __user *)data);
 }
 
+/* We provide getgeo only to please some old bootloader/partitioning tools */
+static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
+{
+        /* some standard values, similar to sd */
+        geo->heads = 1 << 6;
+        geo->sectors = 1 << 5;
+        geo->cylinders = get_capacity(bd->bd_disk) >> 11;
+        return 0;
+}
+
 static struct block_device_operations virtblk_fops = {
-        .ioctl = virtblk_ioctl,
-        .owner = THIS_MODULE,
+        .ioctl  = virtblk_ioctl,
+        .owner  = THIS_MODULE,
+        .getgeo = virtblk_getgeo,
 };
 
 static int virtblk_probe(struct virtio_device *vdev)