-----Original Message-----
From: Greg KH [mailto:greg@kroah.com]
Sent: Friday, September 09, 2011 4:45 PM
To: KY Srinivasan
Cc: gregkh@suse.de; linux-kernel@vger.kernel.org;
devel@linuxdriverproject.org; virtualization@lists.osdl.org; Haiyang Zhang
Subject: Re: [PATCH 18/25] Staging: hv: storvsc: Eliminate the usage of ext field in
struct hv_device

On Thu, Sep 08, 2011 at 07:24:29AM -0700, K. Y. Srinivasan wrote:

quoted

Now, eliminate the usage of ext field in struct  hv_device for storvsc driver.
We do this by registering pointer to struct storvsc_device as the driver
specific data and eliminating the current usage of driver specific data to
save and retrieve the pointer to struct Scsi_Host.
Additionally, all access to the driver specific data is through
the vmbus wrapper functions.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/staging/hv/storvsc_drv.c |   24 +++++++++++++++---------
 1 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/hv/storvsc_drv.c b/drivers/staging/hv/storvsc_drv.c
index 57c1035..98d47cd 100644
--- a/drivers/staging/hv/storvsc_drv.c
+++ b/drivers/staging/hv/storvsc_drv.c

@@ -266,6 +266,7 @@ struct storvsc_device {
 	bool	 destroy;
 	bool	 drain_notify;
 	atomic_t num_outstanding_req;
+	struct Scsi_Host *host;

You are properly reference counting this pointer, right?

The scsi_host_alloc() which we use to allocate the host structure, gives us
the needed reference.

quoted

@@ -306,7 +307,8 @@ static inline struct storvsc_device

*get_out_stor_device(

quoted

 {
 	struct storvsc_device *stor_device;

-	stor_device = (struct storvsc_device *)device->ext;
+	stor_device =
+		(struct storvsc_device *)hv_get_drvdata(device);

Casting is not needed at all.

quoted

@@ -1366,7 +1371,8 @@ static int storvsc_probe(struct hv_device *device,
 	stor_device->destroy = false;
 	init_waitqueue_head(&stor_device->waiting_to_drain);
 	stor_device->device = device;
-	device->ext = stor_device;
+	stor_device->host = host;
+	hv_set_drvdata(device, stor_device);

Lookie there, no reference count incremented, right?  Or did I miss it
somewhere else?

We are stashing the pointer to a structure on which we already have a reference
(that was established at the point of allocating the host).

Regards,

K. Y