linux-kernel - RE: [PATCH v2 0/2] scsi: storvsc: Add support for FC lightweight host.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <DM5PR03MB24902D4813941D2722030DA1A0480@DM5PR03MB2490.namprd03.prod.outlook.com>
Date:   Sun, 29 Jan 2017 00:35:32 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Cathy Avery <cavery@...hat.com>
CC:     Haiyang Zhang <haiyangz@...rosoft.com>,
        "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "dan.carpenter@...cle.com" <dan.carpenter@...cle.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "famz@...hat.com" <famz@...hat.com>
Subject: RE: [PATCH v2 0/2] scsi: storvsc: Add support for FC lightweight
 host.



> -----Original Message-----
> From: Christoph Hellwig [mailto:hch@...radead.org]
> Sent: Thursday, January 26, 2017 6:52 AM
> To: Cathy Avery <cavery@...hat.com>
> Cc: KY Srinivasan <kys@...rosoft.com>; hch@...radead.org; Haiyang Zhang
> <haiyangz@...rosoft.com>; jejb@...ux.vnet.ibm.com;
> martin.petersen@...cle.com; dan.carpenter@...cle.com;
> devel@...uxdriverproject.org; linux-kernel@...r.kernel.org; linux-
> scsi@...r.kernel.org; famz@...hat.com
> Subject: Re: [PATCH v2 0/2] scsi: storvsc: Add support for FC lightweight host.
> 
> On Thu, Jan 26, 2017 at 08:38:58AM -0500, Cathy Avery wrote:
> > Included in the current storvsc driver for Hyper-V is the ability
> > to access luns on an FC fabric via a virtualized fiber channel
> > adapter exposed by the Hyper-V host. This was done to provide an
> > interface for existing customer tools that was more consistent with
> > a conventional FC device. The driver attaches to the FC transport
> > to allow host and port names to be published under
> > /sys/class/fc_host/hostX.
> >
> > A problem arose when attaching to the FC transport. The scsi_scan code
> > attempts to call fc_user_scan which has basically become a no-op
> > due to the virtualized nature of the FC host
> > ( missing rports, vports, etc ). At this point you cannot refresh
> > the scsi bus after mapping or unmapping luns on the SAN without
> > a reboot.
> 
> I don't think a device without rports or vports is a FC device, plain and
> simple.  So as far as I'm concerned we should remove the code from storvsc
> that pretends to be FC, and not add it to virtio to start with.
> 
> And again I think leightweight is a very confusing name -
> what exactly is leight or heavy?   It's really fake or dummy
> in the current version.

Windows has chosen this model for virtualizing FC devices to the guest -
without rports (or vports). As I noted in my earlier email, James came up with
this notion of a lightweight template almost a year ago. We can certainly pick a 
more appropriate name and include better documentation. 
> 
> >
> > 2) Removes an original workaround dealing with replacing
> > the eh_timed_out function. Patch 1 will not set the
> > scsi_transport_template.eh_timed_out function directly during
> > lightweight fc_attach_transport(). It instead relies on
> > whatever was indicated as the scsi_host_template timeout handler
> > during scsi_times_out() scsi_error.c. So the workaround is
> > no longer necessary.
> 
> Can you send a patch that gets rid of the transport class timeout handler
> entirely?  I think it's simply the wrong layering we have here - the
> driver needs to be in control of timeouts, and if it wants it can
> optionally call into library code in the transport class.

We will address this concern.
> 
> 
> FYI, all the long-term relevant explanation need to go into the patches
> themselves (patch description or code comments), not in the cover
> letter.

We will address this.

Regards,

K. Y