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

-----Original Message-----
From: Christoph Hellwig [mailto:hch@infradead.org]
Sent: Thursday, June 30, 2011 3:41 PM
To: KY Srinivasan
Cc: gregkh@suse.de; linux-kernel@vger.kernel.org;
devel@linuxdriverproject.org; virtualization@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:

quoted

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@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Abhishek Kane <redacted>
Signed-off-by: Hank Janssen <redacted>
---
 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,

quoted

 	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