linux-kernel - RE: [PATCH] mpt3sas: Do scsi_remove_host() before deleting SAS PHY objects

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Date:	Mon, 16 May 2016 15:51:48 -0600
From:	Sathya Prakash Veerichetty <sathya.prakash@...adcom.com>
To:	Calvin Owens <calvinowens@...com>,
	"Elliott, Robert (Persistent Memory)" <elliott@....com>
Cc:	Chaitra Basappa <chaitra.basappa@...adcom.com>,
	Suganath Prabu Subramani 
	<suganath-prabu.subramani@...adcom.com>,
	"James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	PDL-MPT-FUSIONLINUX <mpt-fusionlinux.pdl@...adcom.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com
Subject: RE: [PATCH] mpt3sas: Do scsi_remove_host() before deleting SAS PHY objects

Our understanding is the relationship between the SCSI host and SAS end
devices is a parent-child and before ripping of SCSI host we need to rip of
all the children. Why the enclosure ends up trying to re-parent the SCSI
device from the enclosure to the SAS PHY even after we remove the SAS Phy?.
Doesn't this need to be taken care in enclosure_removal?

-----Original Message-----
From: Calvin Owens [mailto:calvinowens@...com]
Sent: Monday, May 16, 2016 2:25 PM
To: Elliott, Robert (Persistent Memory)
Cc: Sathya Prakash; Chaitra P B; Suganath Prabu Subramani; James E.J.
Bottomley; Martin K. Petersen; MPT-FusionLinux.pdl@...adcom.com;
linux-scsi@...r.kernel.org; linux-kernel@...r.kernel.org;
kernel-team@...com; calvinowens@...com
Subject: Re: [PATCH] mpt3sas: Do scsi_remove_host() before deleting SAS PHY
objects

On Friday 05/13 at 21:17 +0000, Elliott, Robert (Persistent Memory) wrote:
>
>
> > -----Original Message-----
> > From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-
> > owner@...r.kernel.org] On Behalf Of Calvin Owens
> > Sent: Friday, May 13, 2016 3:28 PM
> ...
> > Subject: [PATCH] mpt3sas: Do scsi_remove_host() before deleting SAS
> > PHY objects
> >
> ...
> > The issue is that enclosure_remove_device() expects to be able to
> > re-add the device that was previously enclosured: so with SES
> > running, the order we unwind things matters in a way it otherwise
> > wouldn't.
> >
> > Since mpt3sas deletes the SAS objects before the SCSI hosts,
> > enclosure ends up trying to re-parent the SCSI device from the
> > enclosure to the SAS PHY which has already been deleted. This obviously
> > ends in sadness.
> >
> > The fix appears to be simple: just call scsi_remove_host() before we
> > call
> > sas_port_delete() and/or sas_remove_host().
> >
> ...
> > diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> > @@ -8149,6 +8149,8 @@ void scsih_remove(struct pci_dev *pdev)
> >  		_scsih_raid_device_remove(ioc, raid_device);
> >  	}
> >
> > +	scsi_remove_host(shost);
> > +
> >  	/* free ports attached to the sas_host */
> >  	list_for_each_entry_safe(mpt3sas_port, next_port,
> >  	   &ioc->sas_hba.sas_port_list, port_list) { @@ -8172,7 +8174,6 @@
> > void scsih_remove(struct pci_dev *pdev)
> >  	}
> >
> >  	sas_remove_host(shost);
> > -	scsi_remove_host(shost);
> >  	mpt3sas_base_detach(ioc);
> >  	spin_lock(&gioc_lock);
> >  	list_del(&ioc->list);
>
> That change matches the pattern of all other drivers calling
> sas_remove_host, except for one:
> 	drivers/message/fusion/mptsas.c
>
> That consensus means this comment in drivers/scsi/scsi_transport_sas.c
> is wrong:
>
> /**
>  * sas_remove_host  -  tear down a Scsi_Host's SAS data structures
>  * @shost:      Scsi Host that is torn down
>  *
>  * Removes all SAS PHYs and remote PHYs for a given Scsi_Host.
>  * Must be called just before scsi_remove_host for SAS HBAs.
>  */

Yes, exactly: that comment appears to be backwards, and as you say most
drivers appear to do the opposite (I looked at HPSA at least, which calls
sas_port_delete() before scsi_remove_host()).

I suppose I should send a patch to fix the comment as well? It'd be nice to
get some testing to be certain I'm not breaking somebody else's setup by
fixing mine though...

Thanks,
Calvin