linux-kernel - Re: [PATCH 8/19]: SCST SYSFS interface implementation

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Date:	Mon, 11 Oct 2010 14:32:35 -0700
From:	Greg KH <greg@...ah.com>
To:	Vladislav Bolkhovitin <vst@...b.net>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	scst-devel <scst-devel@...ts.sourceforge.net>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	Mike Christie <michaelc@...wisc.edu>,
	Vu Pham <vuhuong@...lanox.com>,
	Bart Van Assche <bart.vanassche@...il.com>,
	James Smart <James.Smart@...lex.Com>,
	Joe Eykholt <jeykholt@...co.com>, Andy Yan <ayan@...vell.com>,
	Chetan Loke <generationgnu@...oo.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Hannes Reinecke <hare@...e.de>,
	Richard Sharpe <realrichardsharpe@...il.com>,
	Daniel Henrique Debonzi <debonzi@...ux.vnet.ibm.com>
Subject: Re: [PATCH 8/19]: SCST SYSFS interface implementation

On Mon, Oct 11, 2010 at 11:29:22PM +0400, Vladislav Bolkhovitin wrote:
> Greg KH, on 10/10/2010 01:20 AM wrote:
> > On Sat, Oct 02, 2010 at 01:46:21AM +0400, Vladislav Bolkhovitin wrote:
> >> +static void scst_tgtt_release(struct kobject *kobj)
> >> +{
> >> +	struct scst_tgt_template *tgtt;
> >> +
> >> +	tgtt = container_of(kobj, struct scst_tgt_template, tgtt_kobj);
> >> +	complete_all(&tgtt->tgtt_kobj_release_cmpl);
> >> +	return;
> > 
> > Don't you also need to free the memory of your kobject here?
> > 
> >> +static void scst_tgt_release(struct kobject *kobj)
> >> +{
> >> +	struct scst_tgt *tgt;
> >> +
> >> +	tgt = container_of(kobj, struct scst_tgt, tgt_kobj);
> >> +	complete_all(&tgt->tgt_kobj_release_cmpl);
> >> +	return;
> > 
> > Same here, no kfree?
> > 
> >> +static void scst_acg_release(struct kobject *kobj)
> >> +{
> >> +	struct scst_acg *acg;
> >> +
> >> +	acg = container_of(kobj, struct scst_acg, acg_kobj);
> >> +	complete_all(&acg->acg_kobj_release_cmpl);
> > 
> > And here.
> 
> Thanks for the review. In all those functions kobjects for simplicity
> are embedded into the outer objects, so they will be freed as part of
> the outer objects free. Hence, kfree() for the kobjects in the release
> functions are not needed.

Sweet, you now have opened yourself up to public ridicule as per the
documentation in the kernel for how to use kobjects!

Nice job :)

Seriously, you CAN NOT DO THIS!  If you embed a kobject in a different
structure, then you have to rely on the kobject to handle the reference
counting for that larger structure.  To do ANYTHING else is a bug and
wrong.

Please read the kobject documentation and fix this code up before
submitting it again.

thanks,

greg k-h
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