Re: [PATCH v2 4/7] megaraid_sas: Send SYNCHRONIZE_CACHE command to firmware

[James Bottomley <jejb@linux.vnet.ibm.com>]

On Fri, 2016-10-21 at 17:38 +0530, Kashyap Desai wrote:
> > -----Original Message-----
> > From: James Bottomley [mailto:jejb@linux.vnet.ibm.com]
> > Sent: Friday, October 21, 2016 4:32 PM
> > To: Sumit Saxena; linux-scsi@vger.kernel.org
> > Cc: martin.petersen@oracle.com; thenzl@redhat.com;
> > kashyap.desai@broadcom.com; stable@vger.kernel.org
> > Subject: Re: [PATCH v2 4/7] megaraid_sas: Send SYNCHRONIZE_CACHE
> > command to firmware
> > 
> > On Thu, 2016-10-20 at 02:05 -0700, Sumit Saxena wrote:
> > > From previous patch we have below changes in v2 - 1.  Updated
> > > change
> > > log.  Provided more detail in change log.
> > > 2.  Agreed to remove module parameter. If we remove module
> > > parameter,
> > > we
> > >     can ask customer to disable WCE on drive to get similar
> > > impact.
> > > 3.  Always Send SYNCHRONIZE_CACHE  for JBOD (non Raid) Device to
> > > Firmware.
> > > 
> > > Current megaraid_sas driver returns SYNCHRONIZE_CACHE(related to
> > > Drive
> > > Cache)  command  back to SCSI layer without sending it down to
> > > firmware as firmware supposed to take care of flushing disk cache
> > > for
> > > all drives belongs to Virtual Disk at the time of system
> > > reboot/shutdown.
> > > 
> > > We evaluate and understood that for Raid Volume, why driver
> > > should not
> > > send SYNC_CACHE command to the Firmware.
> > > There may be a some reason in past, but now it looks to be not
> > > required and we have fixed this issue as part of this patch.
> > > 
> > > Commit- " 02b01e0 [SCSI] megaraid_sas: return sync cache call
> > > with
> > > success"
> > > added the code in driver to return SYNCHRONIZE_CACHE without
> > > sending
> > > it to firmware back in 2007. Earlier MR was mainly for Virtual
> > > Disk,
> > > so same code continue for JBOD as well whenever JBOD support was
> > > added
> > > and it introduced bug that SYNCHRONIZE_CACHE is not passed to FW
> > > for
> > > JBOD (non Raid disk).
> > > 
> > > But our recent analysis indicates that, From Day-1 MR Firmware
> > > always
> > > expect Driver to forward SYNCHRONIZE_CACHE for JBOD (non Raid
> > > disk) to
> > > the Firmware.
> > > We have fixed this as part of this patch.
> > > 
> > >  - Additional background -
> > > There are some instance of MegaRaid FW (E.a Gen2 and Gen2.5 FW)
> > > set
> > > WCE bit for Virtual Disk but firmware does not reply correct
> > > status
> > > for SYNCH_CACHE.
> > > It is very difficult to find out which Device ID and firmware has
> > > capability to manage SYNC_CACHE, so we managed to figure out
> > > which are
> > > the new firmware (canHandleSyncCache is set in scratch pad
> > > register at
> > > 0xB4) and use that interface for correct behavior as explained
> > > above.
> > > 
> > > E.g Liberator/Thunderbolt MegaRaid FW returns SYNC_CACHE as
> > > Unsupported command (this is a firmware bug) and eventually
> > > command
> > > will be failed to SML.
> > > This will cause File system to go Read-only.
> > > 
> > >  - New behavior described -
> > > 
> > > IF application requests SYNCH_CACHE
> > >    IF 'JBOD'
> > >               Driver sends SYNCH_CACHE command to the FW
> > >                FW sends SYNCH_CACHE to drive
> > >                FW obtains status from drive and returns same
> > > status
> > > back to driver
> > >    ELSEIF 'VirtualDisk'
> > >                IF any FW which supports new API bit called
> > > canHandleSyncCache
> > >                               Driver sends SYNCH_CACHE command to
> > > the
> > > FW
> > >                               FW does not send SYNCH_CACHE to
> > > drives
> > >                               FW returns SUCCESS
> > >                ELSE
> > >                               Driver does not send SYNCH_CACHE
> > > command
> > > to the FW.
> > >                               Driver return SUCCESS for that
> > > command.
> > >                ENDIF
> > >     ENDIF
> > > ENDIF
> > > 
> > > CC: stable@vger.kernel.org
> > 
> > Can you please split this into two, so we can backport the bug fix
> > without
> > any of
> > the feature addition junk?
> 
> James  - I am sending new patch making two logical fix as you 
> requested. JBOD fix will be marked for CC:stable and for Virtual disk 
> I will post only for head (not for stable). Let me know if resending 
> complete series is good or resending this patch is better.

This is up to Martin, because he has to sort it out, but I think we can
cope with just the two patches.  The bug fix one has to go into the
fixes branch for immediate application and the rest of the series will
go into the misc branch for the 4.10 merge window.

James


> 
> > 
> > > Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
> > > Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
> > > ---
> > >  drivers/scsi/megaraid/megaraid_sas.h        |  3 +++
> > >  drivers/scsi/megaraid/megaraid_sas_base.c   | 10 ++--------
> > >  drivers/scsi/megaraid/megaraid_sas_fusion.c |  5 +++++
> > >  3 files changed, 10 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/scsi/megaraid/megaraid_sas.h
> > > b/drivers/scsi/megaraid/megaraid_sas.h
> > > index ca86c88..43fd14f 100644
> > > --- a/drivers/scsi/megaraid/megaraid_sas.h
> > > +++ b/drivers/scsi/megaraid/megaraid_sas.h
> > > @@ -1429,6 +1429,8 @@ enum FW_BOOT_CONTEXT {
> > >  #define MR_MAX_REPLY_QUEUES_EXT_OFFSET_SHIFT    14
> > >  #define MR_MAX_MSIX_REG_ARRAY                   16
> > >  #define MR_RDPQ_MODE_OFFSET			0X00800000
> > > +#define MR_CAN_HANDLE_SYNC_CACHE_OFFSET		0X0100000
> > > 0
> > > +
> > >  /*
> > >  * register set for both 1068 and 1078 controllers
> > >  * structure extended for 1078 registers @@ -2140,6 +2142,7 @@
> > > struct
> > > megasas_instance {
> > >  	u8 is_imr;
> > >  	u8 is_rdpq;
> > >  	bool dev_handle;
> > > +	bool fw_sync_cache_support;
> > >  };
> > >  struct MR_LD_VF_MAP {
> > >  	u32 size;
> > > diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c
> > > b/drivers/scsi/megaraid/megaraid_sas_base.c
> > > index 3236632..f7a2ab1 100644
> > > --- a/drivers/scsi/megaraid/megaraid_sas_base.c
> > > +++ b/drivers/scsi/megaraid/megaraid_sas_base.c
> > > @@ -1700,16 +1700,10 @@ inline int megasas_cmd_type(struct
> > > scsi_cmnd
> > > *cmd)
> > >  		goto out_done;
> > >  	}
> > > 
> > > -	switch (scmd->cmnd[0]) {
> > > -	case SYNCHRONIZE_CACHE:
> > > -		/*
> > > -		 * FW takes care of flush cache on its own
> > > -		 * No need to send it down
> > > -		 */
> > > +	if (MEGASAS_IS_LOGICAL(scmd) && (scmd->cmnd[0] ==
> > > SYNCHRONIZE_CACHE) &&
> > > +		(!instance->fw_sync_cache_support)) {
> > >  		scmd->result = DID_OK << 16;
> > >  		goto out_done;
> > 
> > This, minus the  "&& (!instance->fw_sync_cache_support)" is all we
> > need
> > for the
> > bug fix, correct?
> Yes.   I will be sending patch for the same. It need only below check
> for
> JBOD fix.
>        if ((scmd->cmnd[0] == SYNCHRONIZE_CACHE) &&
> MEGASAS_IS_LOGICAL(scmd))
> {
> 
> > 
> > James
> > 
> > > -	default:
> > > -		break;
> > >  	}
> > > 
> > >  	return instance->instancet
> > > ->build_and_issue_cmd(instance,
> > > scmd);
> > > diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c
> > > b/drivers/scsi/megaraid/megaraid_sas_fusion.c
> > > index 2159f6a..2e61306 100644
> > > --- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
> > > +++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
> > > @@ -748,6 +748,11 @@ static int
> > > megasas_create_sg_sense_fusion(struct
> > > megasas_instance *instance)
> > >  		goto fail_fw_init;
> > >  	}
> > > 
> > > +	instance->fw_sync_cache_support = (scratch_pad_2 &
> > > +		MR_CAN_HANDLE_SYNC_CACHE_OFFSET) ? 1 : 0;
> > > +	dev_info(&instance->pdev->dev, "FW supports sync
> > > cache\t:
> > > %s\n",
> > > +		 instance->fw_sync_cache_support ? "Yes" :
> > > "No");
> > > +
> > >  	IOCInitMessage =
> > >  	  dma_alloc_coherent(&instance->pdev->dev,
> > >  			     sizeof(struct
> > > MPI2_IOC_INIT_REQUEST),
> --
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