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[6/7] cxlflash: Fix to avoid unnecessary scan with internal LUNs

Message ID 1457128520-53056-6-git-send-email-ukrishn@linux.vnet.ibm.com (mailing list archive)
State Not Applicable
Headers show

Commit Message

Uma Krishnan March 4, 2016, 9:55 p.m. UTC 
From: "Manoj N. Kumar" <manoj@linux.vnet.ibm.com>

When switching to the internal LUN defined on the
IBM CXL flash adapter, there is an unnecessary
scan occurring on the second port. This scan leads
to the following extra lines in the log:

Dec 17 10:09:00 tul83p1 kernel: [ 3708.561134] cxlflash 0008:00:00.0: cxlflash_queuecommand: (scp=c0000000fc1f0f00) 11/1/0/0 cdb=(A0000000-00000000-10000000-00000000)
Dec 17 10:09:00 tul83p1 kernel: [ 3708.561147] process_cmd_err: cmd failed afu_rc=32 scsi_rc=0 fc_rc=0 afu_extra=0xE, scsi_extra=0x0, fc_extra=0x0

By definition, both of the internal LUNs are on the first port/channel.

When the lun_mode is switched to internal LUN the
same value for host->max_channel is retained. This
causes an unnecessary scan over the second port/channel.

This fix alters the host->max_channel to 0 (1 port), if internal
LUNs are configured and switches it back to 1 (2 ports) while
going back to external LUNs.

Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>
---
 drivers/scsi/cxlflash/main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Matthew R. Ochs March 7, 2016, 6:45 p.m. UTC | #1 
> On Mar 4, 2016, at 3:55 PM, Uma Krishnan <ukrishn@linux.vnet.ibm.com> wrote:
> 
> From: "Manoj N. Kumar" <manoj@linux.vnet.ibm.com>
> 
> When switching to the internal LUN defined on the
> IBM CXL flash adapter, there is an unnecessary
> scan occurring on the second port. This scan leads
> to the following extra lines in the log:
> 
> Dec 17 10:09:00 tul83p1 kernel: [ 3708.561134] cxlflash 0008:00:00.0: cxlflash_queuecommand: (scp=c0000000fc1f0f00) 11/1/0/0 cdb=(A0000000-00000000-10000000-00000000)
> Dec 17 10:09:00 tul83p1 kernel: [ 3708.561147] process_cmd_err: cmd failed afu_rc=32 scsi_rc=0 fc_rc=0 afu_extra=0xE, scsi_extra=0x0, fc_extra=0x0
> 
> By definition, both of the internal LUNs are on the first port/channel.
> 
> When the lun_mode is switched to internal LUN the
> same value for host->max_channel is retained. This
> causes an unnecessary scan over the second port/channel.
> 
> This fix alters the host->max_channel to 0 (1 port), if internal
> LUNs are configured and switches it back to 1 (2 ports) while
> going back to external LUNs.
> 
> Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>

Acked-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Uma Krishnan March 8, 2016, 5:56 p.m. UTC | #2 
On 3/4/2016 3:55 PM, Uma Krishnan wrote:
> From: "Manoj N. Kumar" <manoj@linux.vnet.ibm.com>
>
> When switching to the internal LUN defined on the
> IBM CXL flash adapter, there is an unnecessary
> scan occurring on the second port. This scan leads
> to the following extra lines in the log:
>
> Dec 17 10:09:00 tul83p1 kernel: [ 3708.561134] cxlflash 0008:00:00.0: cxlflash_queuecommand: (scp=c0000000fc1f0f00) 11/1/0/0 cdb=(A0000000-00000000-10000000-00000000)
> Dec 17 10:09:00 tul83p1 kernel: [ 3708.561147] process_cmd_err: cmd failed afu_rc=32 scsi_rc=0 fc_rc=0 afu_extra=0xE, scsi_extra=0x0, fc_extra=0x0
>
> By definition, both of the internal LUNs are on the first port/channel.
>
> When the lun_mode is switched to internal LUN the
> same value for host->max_channel is retained. This
> causes an unnecessary scan over the second port/channel.
>
> This fix alters the host->max_channel to 0 (1 port), if internal
> LUNs are configured and switches it back to 1 (2 ports) while
> going back to external LUNs.
>
> Signed-off-by: Manoj N. Kumar <manoj@linux.vnet.ibm.com>

Reviewed-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com>
diff mbox

Patch

diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
index ca702d8..0f062a4 100644
--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -2097,6 +2097,16 @@  static ssize_t lun_mode_store(struct device *dev,
 	rc = kstrtouint(buf, 10, &lun_mode);
 	if (!rc && (lun_mode < 5) && (lun_mode != afu->internal_lun)) {
 		afu->internal_lun = lun_mode;
+
+		/*
+		 * When configured for internal LUN, there is only one channel,
+		 * channel number 0, else there will be 2 (default).
+		 */
+		if (afu->internal_lun)
+			shost->max_channel = 0;
+		else
+			shost->max_channel = NUM_FC_PORTS - 1;
+
 		afu_reset(cfg);
 		scsi_scan_host(cfg->host);
 	}