Add backing support for HDIO_GETGEO ioctl to blkfront.

Inspired by an earlier patch from Charles Coffing.

Signed-Off-By: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: head-2006-05-11/drivers/xen/blkfront/blkfront.c
===================================================================
--- head-2006-05-11.orig/drivers/xen/blkfront/blkfront.c	2006-05-12 09:39:21.000000000 +0200
+++ head-2006-05-11/drivers/xen/blkfront/blkfront.c	2006-05-15 09:59:52.000000000 +0200
@@ -452,10 +452,6 @@ int blkif_ioctl(struct inode *inode, str
 		      command, (long)argument, inode->i_rdev);
 
 	switch (command) {
-	case HDIO_GETGEO:
-		/* return ENOSYS to use defaults */
-		return -ENOSYS;
-
 	case CDROMMULTISESSION:
 		DPRINTK("FIXME: support multisession CDs later\n");
 		for (i = 0; i < sizeof(struct cdrom_multisession); i++)
@@ -473,6 +469,23 @@ int blkif_ioctl(struct inode *inode, str
 }
 
 
+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;
+}
+
+
 /*
  * blkif_queue_request
  *
Index: head-2006-05-11/drivers/xen/blkfront/block.h
===================================================================
--- head-2006-05-11.orig/drivers/xen/blkfront/block.h	2006-05-12 09:39:21.000000000 +0200
+++ head-2006-05-11/drivers/xen/blkfront/block.h	2006-05-10 11:06:51.000000000 +0200
@@ -140,6 +140,7 @@ extern int blkif_open(struct inode *inod
 extern int blkif_release(struct inode *inode, struct file *filep);
 extern int blkif_ioctl(struct inode *inode, struct file *filep,
                        unsigned command, unsigned long argument);
+extern int blkif_getgeo(struct block_device *, struct hd_geometry *);
 extern int blkif_check(dev_t dev);
 extern int blkif_revalidate(dev_t dev);
 extern void do_blkif_request (request_queue_t *rq);
Index: head-2006-05-11/drivers/xen/blkfront/vbd.c
===================================================================
--- head-2006-05-11.orig/drivers/xen/blkfront/vbd.c	2006-05-12 09:39:21.000000000 +0200
+++ head-2006-05-11/drivers/xen/blkfront/vbd.c	2006-05-10 11:07:16.000000000 +0200
@@ -91,6 +91,7 @@ static struct block_device_operations xl
 	.open = blkif_open,
 	.release = blkif_release,
 	.ioctl  = blkif_ioctl,
+	.getgeo = blkif_getgeo
 };
 
 spinlock_t blkif_io_lock = SPIN_LOCK_UNLOCKED;