When they added getgeo to the block device methods, we kept using
ioctl-based get geometry in the standalone aoe driver, since it has
greater backwards compatibility.  Then on some kernels, the old
ioctl-based method was no longer working, e.g., when blktool tries to
get info about the device.

So now we use the getgeo block device method when it is available.

commit a885c8c4316e1c1d2d2c8755da3f3d14f852528d
Author: Christoph Hellwig <hch@lst.de>
Date:   Sun Jan 8 01:02:50 2006 -0800

    [PATCH] Add block_device_operations.getgeo block device method
    
    HDIO_GETGEO is implemented in most block drivers, and all of them have to
    duplicate the code to copy the structure to userspace, as well as getting
    the start sector.  This patch moves that to common code [1] and adds a
    ->getgeo method to fill out the raw kernel hd_geometry structure.  For many
    drivers this means ->ioctl can go away now.