Date: Wed, 22 Feb 2006 14:28:46 -0800
From: Greg KH <gregkh@suse.de>
To: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
Cc: Neil Brown <neilb@suse.de>, Alasdair Kergon <agk@redhat.com>,
       Lars Marowsky-Bree <lmb@suse.de>, linux-kernel@vger.kernel.org,
       device-mapper development <dm-devel@redhat.com>
Subject: Re: [PATCH 1/3] sysfs representation of stacked devices (common) (rev.2)
Message-ID: <20060222222846.GA14249@suse.de>
References: <43FC8C00.5020600@ce.jp.nec.com> <43FC8D8C.1060904@ce.jp.nec.com> <20060222184853.GB13638@suse.de> <43FCE40A.1010206@ce.jp.nec.com>
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On Wed, Feb 22, 2006 at 05:22:02PM -0500, Jun'ichi Nomura wrote:
> Hi Greg,
> 
> Thanks for comments.
> 
> Greg KH wrote:
> >>+/* This is a mere directory in sysfs. No methods are needed. */
> >>+static struct kobj_type bd_holder_ktype = {
> >>+	.release	= NULL,
> >>+	.sysfs_ops	= NULL,
> >>+	.default_attrs	= NULL,
> >>+};
> >
> >That doesn't look right.  You always need a release function.
> 
> I'll move them out to gendisk/hd_struct creation with proper
> release function.
> 
> I thought it's correct because NULL release function is
> just ignored in kobject_cleanup() and it let outside function
> to release the whole structure.
> But it seems wrong to embed these additional kobjects in
> the structures which are logically separate from them.
> 
> >>+static inline void del_holder_dir(struct block_device *bdev)
> >>+{
> >>+	/*
> >>+	 * Don't kobject_unregister to avoid memory allocation
> >>+	 * in kobject_hotplug.
> >>+	 */
> >>+	kobject_del(&bdev->bd_holder_dir);
> >>+	kobject_put(&bdev->bd_holder_dir);
> >>+}
> >
> >No, do it correctly please.
> 
> OK, I'll change them to kobject_unregister() and do it
> when gendisk/hd_struct is removed.
> Then we can avoid possible memory allocation in dm's atomic
> operation, too.

That sounds great.

thanks,

greg k-h
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