linux-kernel - Re: [PATCH v2 0/5] Re-order scsi_remove_host and sas_remove

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Message-ID: <20170421111941.GA17971@lst.de>
Date:   Fri, 21 Apr 2017 13:19:41 +0200
From:   Christoph Hellwig <hch@....de>
To:     Johannes Thumshirn <jthumshirn@...e.de>
Cc:     "Martin K . Petersen" <martin.petersen@...cle.com>,
        James Bottomley <jejb@...ux.vnet.ibm.com>,
        Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
        Bart Van Assche <Bart.VanAssche@...disk.com>,
        Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Jinpu Wang <jinpu.wang@...fitbricks.com>,
        John Garry <john.garry@...wei.com>, tj@...nel.org
Subject: Re: [PATCH v2 0/5] Re-order scsi_remove_host and sas_remove_host
        in SAS HBA LLDDs

On Fri, Apr 21, 2017 at 10:04:45AM +0200, Johannes Thumshirn wrote:
> This series re-orders the calls to scsi_remove_host() and sas_remove_host() in
> all SAS HBA drivers (apart from mpt3sas which is doing it correctly). This is
> for two reasons:
> 	1) After the change to recursive removal of sysfs entries, we're
> 	   trying to remove already removed kobjects when doing a
> 	   sas_remove_host() _after_ a scsi_remove_host()
> 	2) the documentation mandates it even (becuase of 1)
> 
> Unfortunately this does not completely solve issues with recursive sysfs
> removals in SAS, as libsas has asynchronous behaviour where strong ordering
> would be needed. But I am working on it and I do know other do as well. So if
> anyone else (James, Christoph, Bart, I'm looking at you) has an idea, I do
> have test setups and I'm willing to take input in form of ideas and patches.
> 
> I also dropped the SDEV_CANCEL state change for now. We re-evaluate it once we
> have an idea how to tackle the ordering issues and place it into
> sas_unregister_ha() as per James' comment.

Any reason to not just make sas_remove_host call scsi_remove_host
to ensure we get the ordering right?