linux-kernel - Re: [PATCH 09/62] atm/nicstar: convert to idr

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Message-ID: <20130204170624.GJ27963@mtj.dyndns.org>
Date:	Mon, 4 Feb 2013 09:06:24 -0800
From:	Tejun Heo <tj@...nel.org>
To:	chas williams - CONTRACTOR <chas@....nrl.navy.mil>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	rusty@...tcorp.com.au, bfields@...ldses.org,
	skinsbursky@...allels.com, ebiederm@...ssion.com,
	jmorris@...ei.org, axboe@...nel.dk, netdev@...r.kernel.org
Subject: Re: [PATCH 09/62] atm/nicstar: convert to idr_alloc()

Hello, Chas.

On Mon, Feb 04, 2013 at 09:04:10AM -0500, chas williams - CONTRACTOR wrote:
> I don't quite understand your comment.  idr_pre_get() returns 0 in the
> case of failure.

So, if you do the following,

	int id1 = 0, id2 = 0;

	if (!id1)
		err = idr_get_new_above(&card->idr, handle1, 0, &id1);
	if (!id2 && err == 0)
		err = idr_get_new_above(&card->idr, handle2, 0, &id2);
	if (err)
		goto out;
									    
You have no way of telling whether id1/2 are allocated or not.  0 is
the special "not allocated" value but it also is a valid ID.  The
error path should be freeing id1/2 if either of them has been
allocated but it doesn't and can't with 0 as the non-allocated value.

Thanks.

-- 
tejun
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