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SubjectRE: [PATCH 18/25] Staging: hv: storvsc: Eliminate the usage of ext field in struct hv_device
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> -----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:
> > 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.
>
> > @@ -306,7 +307,8 @@ static inline struct storvsc_device
> *get_out_stor_device(
> > {
> > 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.
>
> > @@ -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


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