Re: [PATCH V3 1/7] Drivers: scsi: storvsc: Change the limits to reflect the values on the host

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On 07/12/2014 06:48 PM, K. Y. Srinivasan wrote:
Hyper-V hosts can support multiple targets and multiple channels and larger number of
LUNs per target. Update the code to reflect this. With this patch we can correctly
enumerate all the paths in a multi-path storage environment.

In this version of the patch I have addressed comments from
Christoph Hellwig <hch@xxxxxxxxxxxxx>

Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
  drivers/scsi/storvsc_drv.c |   47 +++++++++++++++++++++++++++++---------------
  1 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 9969fa1..8938b13 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -330,17 +330,17 @@ static int storvsc_timeout = 180;

  static void storvsc_on_channel_callback(void *context);

-/*
- * In Hyper-V, each port/path/target maps to 1 scsi host adapter.  In
- * reality, the path/target is not used (ie always set to 0) so our
- * scsi host adapter essentially has 1 bus with 1 target that contains
- * up to 256 luns.
- */
-#define STORVSC_MAX_LUNS_PER_TARGET			64
-#define STORVSC_MAX_TARGETS				1
-#define STORVSC_MAX_CHANNELS				1
+#define STORVSC_MAX_LUNS_PER_TARGET			255
+#define STORVSC_MAX_TARGETS				2
+#define STORVSC_MAX_CHANNELS				8

+#define STORVSC_FC_MAX_LUNS_PER_TARGET			255
+#define STORVSC_FC_MAX_TARGETS				128
+#define STORVSC_FC_MAX_CHANNELS				8

+#define STORVSC_IDE_MAX_LUNS_PER_TARGET			64
+#define STORVSC_IDE_MAX_TARGETS				1
+#define STORVSC_IDE_MAX_CHANNELS			1

  struct storvsc_cmd_request {
  	struct list_head entry;
Limiting max_lun to 255 will make the driver to _not_ respond to LUNs higher than that; ie Well-known LUN won't work here. Also the SCSI stack will be using REPORT LUNS anyway since you're advertising SPC-2 compliance. So your driver runs into issues if Hyper-V would ever return more than 256 LUNs with the REPORT LUN command or if any of the LUNs has an addressing scheme other than
'0x00'.
I would suggest to raise this to the technical limit (ie the largest LUN which the _protocol_ supports) and let REPORT LUNS deal with the actual LUNs.

Cheers,

Hannes
--
Dr. Hannes Reinecke		      zSeries & Storage
hare@xxxxxxx			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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