sunvdc: compute vdisk geometry from capacity

The LDom diskserver doesn't return reliable geometry data. In addition,
the types for all fields in the vio_disk_geom are u16, which were being
truncated in the cast into the u8's of the Linux struct hd_geometry.

Modify vdc_getgeo() to compute the geometry from the disk's capacity in a
manner consistent with xen-blkfront::blkif_getgeo().

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 9 deletions

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index 66ddf704ad7f..1616ad091a5e 100644
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -70,7 +70,6 @@ struct vdc_port {
 
         char                    disk_name[32];
 
-        struct vio_disk_geom    geom;
         struct vio_disk_vtoc    label;
 };
 
@@ -103,11 +102,15 @@ static inline u32 vdc_tx_dring_avail(struct vio_dring_state *dr)
 static int vdc_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 {
         struct gendisk *disk = bdev->bd_disk;
-        struct vdc_port *port = disk->private_data;
+        sector_t nsect = get_capacity(disk);
+        sector_t cylinders = nsect;
 
-        geo->heads = (u8) port->geom.num_hd;
-        geo->sectors = (u8) port->geom.num_sec;
-        geo->cylinders = port->geom.num_cyl;
+        geo->heads = 0xff;
+        geo->sectors = 0x3f;
+        sector_div(cylinders, geo->heads * geo->sectors);
+        geo->cylinders = cylinders;
+        if ((sector_t)(geo->cylinders + 1) * geo->heads * geo->sectors < nsect)
+                geo->cylinders = 0xffff;
 
         return 0;
 }
@@ -714,16 +717,18 @@ static int probe_disk(struct vdc_port *port)
                 if (port->vdisk_size == -1)
                         return -ENODEV;
         } else {
+                struct vio_disk_geom geom;
+
                 err = generic_request(port, VD_OP_GET_DISKGEOM,
-                                      &port->geom, sizeof(port->geom));
+                                      &geom, sizeof(geom));
                 if (err < 0) {
                         printk(KERN_ERR PFX "VD_OP_GET_DISKGEOM returns "
                                "error %d\n", err);
                         return err;
                 }
-                port->vdisk_size = ((u64)port->geom.num_cyl *
-                                    (u64)port->geom.num_hd *
-                                    (u64)port->geom.num_sec);
+                port->vdisk_size = ((u64)geom.num_cyl *
+                                    (u64)geom.num_hd *
+                                    (u64)geom.num_sec);
         }
 
         q = blk_init_queue(do_vdc_request, &port->vio.lock);