[PATCH] xen: Implement getgeo for Xen virtual block device.

[Jeremy Fitzhardinge <jeremy@goop.org>]

The below implements the getgeo hook for Xen block devices. Extracted
from the xen-unstable tree where it has been used for ages.

It is useful to have because it allows things like grub2 (used by the
Debian installer images) to work in a guest domain without having to
sprinkle Xen specific hacks around the place.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
From: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>

---
 drivers/block/xen-blkfront.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

===================================================================
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -37,6 +37,7 @@
 
 #include <linux/interrupt.h>
 #include <linux/blkdev.h>
+#include <linux/hdreg.h>
 #include <linux/module.h>
 
 #include <xen/xenbus.h>
@@ -134,6 +135,22 @@ static void blkif_restart_queue_callback
 {
 	struct blkfront_info *info = (struct blkfront_info *)arg;
 	schedule_work(&info->work);
+}
+
+int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
+{
+	/* We don't have real geometry info, but let's at least return
+	   values consistent with the size of the device */
+	sector_t nsect = get_capacity(bd->bd_disk);
+	sector_t cylinders = nsect;
+
+	hg->heads = 0xff;
+	hg->sectors = 0x3f;
+	sector_div(cylinders, hg->heads * hg->sectors);
+	hg->cylinders = cylinders;
+	if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
+		hg->cylinders = 0xffff;
+	return 0;
 }
 
 /*
@@ -946,6 +963,7 @@ static struct block_device_operations xl
 	.owner = THIS_MODULE,
 	.open = blkif_open,
 	.release = blkif_release,
+	.getgeo = blkif_getgeo,
 };