From: Jim Houston <jim.houston@ccur.com>
To: Hoang-Nam Nguyen <hnguyen@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, openib-general@openib.org,
Stefan Roscher <ossrosch@linux.vnet.ibm.com>,
linuxppc-dev@ozlabs.org, raisch@de.ibm.com,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: idr_get_new_above() limitation?
Date: Mon, 02 Jul 2007 20:31:40 -0400 [thread overview]
Message-ID: <1183422700.3130.27.camel@localhost.localdomain> (raw)
In-Reply-To: <200707021919.27251.hnguyen@linux.vnet.ibm.com>
On Mon, 2007-07-02 at 19:19 +0200, Hoang-Nam Nguyen wrote:
> i=3fffffff token=3fffffff t=000000003fffffff
> i=40000000 token=40000000 t=0000000000000000
> Invalid object 0000000000000000. Expected 40000000
>
> That means token 0x40000000 seems to be the "upper boundary" of idr_find().
> However the behaviour is not consistent in that it was returned by
> idr_get_new_above().
Hi Nam,
Yes this is a bug. Thanks for the great test module.
The problem is in idr_get_new_above_int() in the loop which
adds new layers to the top of the radix tree. It is failing
the "layers < (MAX_LEVEL - 1)" test. It doesn't allocate the
new layer but still calls sub_alloc() which relies on having
the new layer properly constructed. I believe that it is
allocating the slot which corresponds to id = 0.
I believe this is an off by one error in calculating the
MAX_LEVEL value. I will do a more careful review and post
a fix in the next day or so. I have been in Ottawa for OLS.
I'm flying home tomorrow.
Jim Houston - Concurrent Computer Corp.
next prev parent reply other threads:[~2007-07-03 0:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-02 17:19 idr_get_new_above() limitation? Hoang-Nam Nguyen
2007-07-02 22:56 ` Andrew Morton
2007-07-03 0:31 ` Jim Houston [this message]
2007-07-04 14:11 ` Hoang-Nam Nguyen
2007-07-10 20:05 ` [PATCH] fix idr_get_new_above id alias bugs Jim Houston
2007-07-11 19:27 ` Hoang-Nam Nguyen
2007-07-12 21:35 ` Andrew Morton
2007-07-12 21:56 ` Chuck Ebbert
2007-07-13 3:46 ` Tejun Heo
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