linux-kernel - Re: [RFC 22/22] tcm_loop: Add multi-fabric Linux/SCSI LLD fabric module

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Message-ID: <20100906053845.GG17212@core.coreip.homeip.net>
Date:	Sun, 5 Sep 2010 22:38:46 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
Cc:	Greg KH <gregkh@...e.de>, linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Mike Christie <michaelc@...wisc.edu>,
	Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
	James Bottomley <James.Bottomley@...e.de>,
	Jens Axboe <axboe@...nel.dk>,
	Boaz Harrosh <bharrosh@...asas.com>
Subject: Re: [RFC 22/22] tcm_loop: Add multi-fabric Linux/SCSI LLD fabric
 module

On Sun, Sep 05, 2010 at 10:21:20PM -0700, Nicholas A. Bellinger wrote:
> On Sun, 2010-09-05 at 22:17 -0700, Greg KH wrote:
> > On Sun, Sep 05, 2010 at 10:08:16PM -0700, Dmitry Torokhov wrote:
> > > On Sun, Sep 05, 2010 at 02:51:19PM -0700, Nicholas A. Bellinger wrote:
> > > > On Sun, 2010-09-05 at 13:30 -0700, Dmitry Torokhov wrote:
> > > > > On Mon, Aug 30, 2010 at 02:23:23AM -0700, Nicholas A. Bellinger wrote:
> > > > > > +
> > > > > > +static void tcm_loop_primary_release(struct device *dev)
> > > > > > +{
> > > > > > +	return;
> > > > > > +}
> > > > > > +
> > > > > > +static struct device tcm_loop_primary = {
> > > > > > +	.init_name		= "tcm_loop_0",
> > > > > > +	.release		= tcm_loop_primary_release,
> > > > > > +};
> > > > > > +
> > > > > 
> > > > > No, you can not have statically allocated devices and dummy release
> > > > > functions.
> > > > > 
> > > > 
> > > > Last time I checked this is still what mainline
> > > > drivers/scsi/scsi_debug.c is doing for struct device pseudo_primary:
> > > > 
> > > > static void pseudo_0_release(struct device *dev)
> > > > {
> > > >         if (SCSI_DEBUG_OPT_NOISE & scsi_debug_opts)
> > > >                 printk(KERN_INFO "scsi_debug: pseudo_0_release() called\n");
> > > > }
> > > > 
> > > > static struct device pseudo_primary = {
> > > >         .init_name      = "pseudo_0",
> > > >         .release        = pseudo_0_release,
> > > > };
> > > > 
> > > > so for these type of things in TCM_Loop I tend to follow what scsi_debug does,
> > > >  so I don't exactly see a issue here atm.  Anybody else have comments..?
> > > 
> > > The kobject embedded in the device structure is refcounted and it's
> > > lifetime may be different from lifetime of your module. If somebody
> > > happen to hold reference to the driver while your module is being
> > > unloaded bad things will happen.
> > > 
> > > I am sure Greg has something on this topic ready for cut-and-paste.
> > 
> > Documentation/kobject.txt :)
> 
> I still don't get it..?  Does this mean that scsi_debug and TCM_Loop are
> currently broken wrt to this item or not..?
> 

Yes they are broken.

-- 
Dmitry
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