[PATCH] scsi_scan: move 'INQUIRY result too short' message to debug level

[PATCH] scsi_scan: move 'INQUIRY result too short' message to debug level

[Vitaly Kuznetsov]

Some Hyper-V hosts are known for ignoring SPC-2/3/4 requirement
for 'INQUIRY data (see table ...) shall contain at least 36 bytes'. As a
result we get tons on 'scsi 0:7:1:1: scsi scan: INQUIRY result too short
(5), using 36' messages on console. As Hyper-V is also known for its
serial port being extremely slow multi-VCPU guests we get CPU blocked
putting these (useless) messages on console (e.g. happens when we add
multiple disks). Move them to debug level.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/scsi/scsi_scan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index f9f3f82..cb5c50a 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -701,7 +701,7 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
 	 * strings.
 	 */
 	if (sdev->inquiry_len < 36) {
-		sdev_printk(KERN_INFO, sdev,
+		sdev_printk(KERN_DEBUG, sdev,
 			    "scsi scan: INQUIRY result too short (%d),"
 			    " using 36\n", sdev->inquiry_len);
 		sdev->inquiry_len = 36;
-- 
2.4.3

RE: [PATCH] scsi_scan: move 'INQUIRY result too short' message to debug level

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, August 31, 2015 5:50 AM
> To: James E.J. Bottomley <JBottomley@odin.com>
> Cc: linux-scsi@vger.kernel.org; linux-kernel@vger.kernel.org; KY Srinivasan
> <kys@microsoft.com>; Long Li <longli@microsoft.com>; Dexuan Cui
> <decui@microsoft.com>
> Subject: [PATCH] scsi_scan: move 'INQUIRY result too short' message to
> debug level
> 
> Some Hyper-V hosts are known for ignoring SPC-2/3/4 requirement
> for 'INQUIRY data (see table ...) shall contain at least 36 bytes'. As a
> result we get tons on 'scsi 0:7:1:1: scsi scan: INQUIRY result too short
> (5), using 36' messages on console. As Hyper-V is also known for its
> serial port being extremely slow multi-VCPU guests we get CPU blocked
> putting these (useless) messages on console (e.g. happens when we add
> multiple disks). Move them to debug level.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/scsi/scsi_scan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index f9f3f82..cb5c50a 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -701,7 +701,7 @@ static int scsi_probe_lun(struct scsi_device *sdev,
> unsigned char *inq_result,
>  	 * strings.
>  	 */
>  	if (sdev->inquiry_len < 36) {
> -		sdev_printk(KERN_INFO, sdev,
> +		sdev_printk(KERN_DEBUG, sdev,
>  			    "scsi scan: INQUIRY result too short (%d),"
>  			    " using 36\n", sdev->inquiry_len);
>  		sdev->inquiry_len = 36;
> --
> 2.4.3

Re: [PATCH] scsi_scan: move 'INQUIRY result too short' message to debug level

[James Bottomley]

On Mon, 2015-08-31 at 14:50 +0200, Vitaly Kuznetsov wrote:
> Some Hyper-V hosts are known for ignoring SPC-2/3/4 requirement
> for 'INQUIRY data (see table ...) shall contain at least 36 bytes'. As a
> result we get tons on 'scsi 0:7:1:1: scsi scan: INQUIRY result too short
> (5), using 36' messages on console. As Hyper-V is also known for its
> serial port being extremely slow multi-VCPU guests we get CPU blocked
> putting these (useless) messages on console (e.g. happens when we add
> multiple disks). Move them to debug level.

This isn't an ignorable debug message.  It means the inquiry information
the system relies on will be false, so it's fairly essential for bug
reports.  It could be made a once per device print, but I don't think we
can eliminate it.

James

> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  drivers/scsi/scsi_scan.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index f9f3f82..cb5c50a 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -701,7 +701,7 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
>  	 * strings.
>  	 */
>  	if (sdev->inquiry_len < 36) {
> -		sdev_printk(KERN_INFO, sdev,
> +		sdev_printk(KERN_DEBUG, sdev,
>  			    "scsi scan: INQUIRY result too short (%d),"
>  			    " using 36\n", sdev->inquiry_len);
>  		sdev->inquiry_len = 36;

Re: [PATCH] scsi_scan: move 'INQUIRY result too short' message to debug level

[Vitaly Kuznetsov]

James Bottomley <James.Bottomley@HansenPartnership.com> writes:

> On Mon, 2015-08-31 at 14:50 +0200, Vitaly Kuznetsov wrote:
>> Some Hyper-V hosts are known for ignoring SPC-2/3/4 requirement
>> for 'INQUIRY data (see table ...) shall contain at least 36 bytes'. As a
>> result we get tons on 'scsi 0:7:1:1: scsi scan: INQUIRY result too short
>> (5), using 36' messages on console. As Hyper-V is also known for its
>> serial port being extremely slow multi-VCPU guests we get CPU blocked
>> putting these (useless) messages on console (e.g. happens when we add
>> multiple disks). Move them to debug level.
>
> This isn't an ignorable debug message.  It means the inquiry information
> the system relies on will be false, so it's fairly essential for bug
> reports.  It could be made a once per device print, but I don't think we
> can eliminate it.

I see. What if we introduce a special flag to mark such known-as-broken
hosts? E.g.:

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index f9f3f82..c6ffb5c 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -701,9 +701,10 @@ static int scsi_probe_lun(struct scsi_device *sdev, unsigned char *inq_result,
 	 * strings.
 	 */
 	if (sdev->inquiry_len < 36) {
-		sdev_printk(KERN_INFO, sdev,
-			    "scsi scan: INQUIRY result too short (%d),"
-			    " using 36\n", sdev->inquiry_len);
+		if (!sdev->host->hostt->short_inquiry)
+			sdev_printk(KERN_INFO, sdev,
+				    "scsi scan: INQUIRY result too short (%d),"
+				    " using 36\n", sdev->inquiry_len);
 		sdev->inquiry_len = 36;
 	}
 
diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 3c6584f..f3b4d0f 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1711,6 +1711,7 @@ static struct scsi_host_template scsi_driver = {
 	/* Make sure we dont get a sg segment crosses a page boundary */
 	.dma_boundary =		PAGE_SIZE-1,
 	.no_write_same =	1,
+	.short_inquiry =	1,
 };
 
 enum {
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index e113c75..04aefad 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -454,6 +454,12 @@ struct scsi_host_template {
 	unsigned no_async_abort:1;
 
 	/*
+	 * True if this host adapter returns short (<36 bytes) resposes to
+	 * INQUIRY requests.
+	 */
+	unsigned short_inquiry:1;
+
+	/*
 	 * Countdown for host blocking with no commands outstanding.
 	 */
 	unsigned int max_host_blocked;

-- 
  Vitaly