Re: Patch: lpfc: Modify Emulex lpfc LPFC_DEFAULT_SG_SEG_CNT to 128 for default larger sg_io capability

[Laurence Oberman <loberman@redhat.com>]

----- Original Message -----
> From: "Laurence Oberman" <loberman@redhat.com>
> To: "Linux SCSI List" <linux-scsi@vger.kernel.org>
> Sent: Wednesday, February 8, 2017 3:07:12 PM
> Subject: Patch: lpfc: Modify Emulex lpfc LPFC_DEFAULT_SG_SEG_CNT to 128 for default larger sg_io capability
> 
> We have been seeing issues with qemu_kvm virtual guests where if they issue
> I/O to direct attached SCSI passthrough LUNS with large I/O sizes such as
> 512K
> the sg_io will fail with -EINVAL.
> 
> Simple reproducer is here.
> 
> strace -e ioctl sg_dd if=/dev/zero of=/dev/sdae bpt=0x400 count=0x400
> blk_sgio=1
> Assume default 'bs' (block size) of 512 bytes
> ioctl(4, SG_IO, {'S', SG_DXFER_FROM_DEV, cmd[6]=[12, 00, 00, 00, 24, 00],
> mx_sb_len=64, iovec_count=0, dxfer_len=36, timeout=60000, flags=0,
> data[36]=["\0\0\5\2\37\270\0\2LIO-ORG block-15        "...], status=00,
> masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0,
> duration=0, info=0}) = 0
> ioctl(4, SG_IO, {'S', SG_DXFER_TO_DEV, cmd[10]=[2a, 00, 00, 00, 00, 00, 00,
> 04, 00, 00], mx_sb_len=64, iovec_count=0, dxfer_len=524288, timeout=60000,
> flags=0,
> data[524288]=["\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...]})
> = -1 EINVAL (Invalid argument)
> writing (SG_IO) on sg device, error: Invalid argument
> sg_write failed, seek=0
> Some error occurred,  remaining block count=1024
> 1024+0 records in
> 0+0 records out
> 
> Qlogic defaults to 128 so has not been seeing this but lpfc does not.
> Would like to avoid having to set this in the module parameters to 128.
> 
> Tested-by:     Laurence Oberman <loberman@redhat.com>
> Signed-off-by: Laurence Oberman <loberman@redhat.com>
> 
> From 23996dcbdd9b505d18d59ecde961c87f76fc9c2e Mon Sep 17 00:00:00 2001
> From: Laurence Oberman <loberman@redhat.com>
> Date: Wed, 8 Feb 2017 14:49:05 -0500
> Subject: [PATCH] Modified LPFC_DEFAULT_SG_SEG_CNT to 128 to match Qlogic.
> This
>  will allow larger sg_io passthrough for qemu_kvm guests that expect the
>  larger setting for I/O large rthen 512k.
> 
> ---
>  drivers/scsi/lpfc/lpfc.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/lpfc/lpfc.h b/drivers/scsi/lpfc/lpfc.h
> index 8a20b4e..8f86d41 100644
> --- a/drivers/scsi/lpfc/lpfc.h
> +++ b/drivers/scsi/lpfc/lpfc.h
> @@ -42,7 +42,7 @@
>  #define LPFC_MAX_NS_RETRY	3	/* Number of retry attempts to contact
>  					   the NameServer  before giving up. */
>  #define LPFC_CMD_PER_LUN	3	/* max outstanding cmds per lun */
> -#define LPFC_DEFAULT_SG_SEG_CNT 64	/* sg element count per scsi cmnd */
> +#define LPFC_DEFAULT_SG_SEG_CNT 128	/* sg element count per scsi cmnd */
>  #define LPFC_DEFAULT_MENLO_SG_SEG_CNT 128	/* sg element count per scsi
>  		cmnd for menlo needs nearly twice as for firmware
>  		downloads using bsg */
> --
> 1.8.3.1
> 
> 
> 
>  
> 

Replying to my own email

I was wondering if we could set it to 256 as the default.
This seems to pass sg_io all the way to 0x800

bpt=0x200
Assume default 'bs' (block size) of 512 bytes
ioctl(4, SG_IO, {'S', SG_DXFER_FROM_DEV, cmd[6]=[12, 00, 00, 00, 24, 00], mx_sb_len=64, iovec_count=0, dxfer_len=36, timeout=60000, flags=0, data[36]=["\0\0\5\2\37\270\0\2LIO-ORG block-21        "...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=0, info=0}) = 0
ioctl(4, SG_IO, {'S', SG_DXFER_TO_DEV, cmd[10]=[2a, 00, 00, 00, 00, 00, 00, 02, 00, 00], mx_sb_len=64, iovec_count=0, dxfer_len=262144, timeout=60000, flags=0, data[262144]=["\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=30, info=0}) = 0
512+0 records in
512+0 records out
+++ exited with 0 +++

bpt=0x400
Assume default 'bs' (block size) of 512 bytes
ioctl(4, SG_IO, {'S', SG_DXFER_FROM_DEV, cmd[6]=[12, 00, 00, 00, 24, 00], mx_sb_len=64, iovec_count=0, dxfer_len=36, timeout=60000, flags=0, data[36]=["\0\0\5\2\37\270\0\2LIO-ORG block-21        "...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=0, info=0}) = 0
ioctl(4, SG_IO, {'S', SG_DXFER_TO_DEV, cmd[10]=[2a, 00, 00, 00, 00, 00, 00, 04, 00, 00], mx_sb_len=64, iovec_count=0, dxfer_len=524288, timeout=60000, flags=0, data[524288]=["\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=43, info=0}) = 0
1024+0 records in
1024+0 records out
+++ exited with 0 +++

bpt=0x800
Assume default 'bs' (block size) of 512 bytes
ioctl(4, SG_IO, {'S', SG_DXFER_FROM_DEV, cmd[6]=[12, 00, 00, 00, 24, 00], mx_sb_len=64, iovec_count=0, dxfer_len=36, timeout=60000, flags=0, data[36]=["\0\0\5\2\37\270\0\2LIO-ORG block-21        "...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=0, info=0}) = 0
ioctl(4, SG_IO, {'S', SG_DXFER_TO_DEV, cmd[10]=[2a, 00, 00, 00, 00, 00, 00, 08, 00, 00], mx_sb_len=64, iovec_count=0, dxfer_len=1048576, timeout=60000, flags=0, data[1048576]=["\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...], status=00, masked_status=00, sb[0]=[], host_status=0, driver_status=0, resid=0, duration=34, info=0}) = 0
2048+0 records in
2048+0 records out
+++ exited with 0 +++

Thanks
Laurence