[PATCH 24/40] Staging: hv: storvsc: On I/O get the correct IDE device

KY Srinivasan kys at microsoft.com
Thu Jun 30 21:15:54 UTC 2011



> -----Original Message-----
> From: Christoph Hellwig [mailto:hch at infradead.org]
> Sent: Thursday, June 30, 2011 3:41 PM
> To: KY Srinivasan
> Cc: gregkh at suse.de; linux-kernel at vger.kernel.org;
> devel at linuxdriverproject.org; virtualization at lists.osdl.org; Haiyang Zhang;
> Abhishek Kane (Mindtree Consulting PVT LTD); Hank Janssen
> Subject: Re: [PATCH 24/40] Staging: hv: storvsc: On I/O get the correct IDE device
> 
> On Wed, Jun 29, 2011 at 07:39:21AM -0700, K. Y. Srinivasan wrote:
> > We use the channel number to distinguish an IDE device managed by the
> > storvsc driver from scsi devices. Add code to get the correct
> > device pointer based on the channel number.
> >
> > Signed-off-by: K. Y. Srinivasan <kys at microsoft.com>
> > Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
> > Signed-off-by: Abhishek Kane <v-abkane at microsoft.com>
> > Signed-off-by: Hank Janssen <hjanssen at microsoft.com>
> > ---
> >  drivers/staging/hv/storvsc_drv.c |   10 ++++++++++
> >  1 files changed, 10 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/staging/hv/storvsc_drv.c b/drivers/staging/hv/storvsc_drv.c
> > index cf659d7..fcc3f5d 100644
> > --- a/drivers/staging/hv/storvsc_drv.c
> > +++ b/drivers/staging/hv/storvsc_drv.c
> > @@ -517,6 +517,16 @@ static int storvsc_queuecommand_lck(struct scsi_cmnd
> *scmnd,
> >  	unsigned int sg_count = 0;
> >  	struct vmscsi_request *vm_srb;
> >
> > +	if (scmnd->device->channel >= HV_IDE_BASE_CHANNEL) {
> > +		int channel = scmnd->device->channel;
> > +
> > +		/*
> > +		 * This is an IDE device; get the right dev.
> > +		 */
> > +
> > +		dev = ide_devices[channel - HV_IDE_BASE_CHANNEL];
> > +	}
> 
> So instead of playing games about getting the right hv_device here,
> why don't you register one scsi host for each IDE device? libata
> does the same for real ATA devices.
> 
That is what I did initially. Then looking at the way we  were handling scsi devices
where each scsi controller configured for the guest results in an emulated HBA
(scsi host) in the guest and all the block devices under a given controller are
handled through this one host, I decided to mimic a similar structure  - one
scsi host for all the block devices configured as an IDE device.

I can go back to my earlier implementation with one host per disk.

Regards,

K. Y 



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