Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Liam Howlett <liam.howlett@oracle.com>
To:     Andrew Morton <akpm@linux-foundation.org>
CC:     "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        Andrei Vagin <avagin@gmail.com>,
        "usama.anjum@collabora.com" <usama.anjum@collabora.com>,
        Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH] maple_tree: Fix mas_spanning_rebalance() on insufficient
 data
Thread-Topic: [PATCH] maple_tree: Fix mas_spanning_rebalance() on insufficient
 data
Thread-Index: AQHZEX+nAbpIKZyMBUWjTfJJigFqH65w3qiAgAAdhwA=
Date:   Fri, 16 Dec 2022 20:47:27 +0000
Message-ID: <20221216204720.of5vectluqg6nd4k@revolver>
References: <20221216185233.2036415-1-Liam.Howlett@oracle.com>
 <20221216110139.fe9b0cc2951014e1856d0042@linux-foundation.org>
In-Reply-To: <20221216110139.fe9b0cc2951014e1856d0042@linux-foundation.org>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?bQtvfZ1pl3W3zkcy4bFR2nxvpvM0EVOQQZMYDexNULuTKFr6VzAGfvRO5LxC?=
 =?us-ascii?Q?x84laSbSsg9hv/r75+nXPM5MDJ9YX31IGGA9CDXoLv4J27MbCyiLQQc+LlTL?=
 =?us-ascii?Q?J2mOpM0dcK1TDwbf5i6k739FbWZeVcOHfi3aHHIJHY8X/0JrQrasKuHOKNXy?=
 =?us-ascii?Q?Wzr4bQxVKrJb+8iY3Gca9kr9OOLWbqvmwqVxz4yftHfFL9FEuTSqonZhwMoo?=
 =?us-ascii?Q?ZWmPAn7jLd4Rv02cWyQDu6bLaz9j28pa9EjZTrCVM602LoBwiJuCpz9suAbX?=
 =?us-ascii?Q?DuUz0+tuz1H4cz+KMveB9q06QJ4aSS8PxyzDH/00aYnXCylz5oG2S6UdnGcZ?=
 =?us-ascii?Q?R99Vaq+1nXDj+0opvF9AaEo5O6q5PoSlgraUW1K2ovqSJdbMz7CvsubEmaTL?=
 =?us-ascii?Q?LNhJ3NRVFWQGeCip8mHS44gePF/+BiwmAMKe079Bq3F+hSu+Yem7Gf+qvdMu?=
 =?us-ascii?Q?HyJ0nSfX7WP5tok4fzran71Bg6blB6slmZuoS5B+Jy9UZu13ux7ImIioIYWa?=
 =?us-ascii?Q?bNutE68v7AyiFhOsRN90Ew8UWU0n7J+rIKL48ecNRynpejKaZz3Shj9BV9ok?=
 =?us-ascii?Q?PL8duhsn1dSH4aT4x34XRYSjZ/ry0DrdaKfflmRTcAWRbpF3dp0wBEQCzoq/?=
 =?us-ascii?Q?mNmIH8BPk1Np4zv4CkXQqg90IqMxEwrxoFb1yGDmFt8slYzaYVO7WbRk0uR9?=
 =?us-ascii?Q?SAz6w/1n9TqZgkomPv5t2kOPmbt55Tgr/9C62BIQzJopyQTGTt8meG9TmMA7?=
 =?us-ascii?Q?uaE7SLqzGLeeJoWXXgPhTCCCG2j9hUNPjLCJrD9OXMw/um09tx08n0BmfQ59?=
 =?us-ascii?Q?+VcTSUfIvB+CIu/e63akmdCh/l7TA1zc4UaS6sv6e1PqZ4elZanHL4RF0raC?=
 =?us-ascii?Q?PwN/dpTB+f7rFJ29a2A6xPFXp7d6PJLnyRH3GpAjfRWFmTrwWALz+d6ENFY/?=
 =?us-ascii?Q?8UWSR9VP3rwfWBKiLmYXrOCSej57s8/buZUISY53XdlqjYAaJKmIyzlLYHiC?=
 =?us-ascii?Q?ZJ1g/rk8PxOsjIxItjLZLlxW5in1EyIloz1ka3U12U/5FtSt3h9o/7TG7rz/?=
 =?us-ascii?Q?8Kb3If/wTdZ82X7bmpVCE/QF/eGlIk52AExOV1vwTTqJiAd5FCg3slRS2gn3?=
 =?us-ascii?Q?4K6N7wtUSG6hgeRK0WtxXm7hCqG80CZOMY/H2hZRBg8IfR5b8BVSKeTmcf9O?=
 =?us-ascii?Q?DmpvPzxWmgzWvpylGOBlc4B/dKtT1lZjg0fc3q7u65FwyIVQaRdtl6aRi0Ji?=
 =?us-ascii?Q?S9iHABEvGc4d+nyPYOdeP8MFldABWEtL2/Gu/mvk0HAx6uukva83lzm0/BdW?=
 =?us-ascii?Q?4zjfoWPSnWTwZT9EOi7K1Xmnniscb7m2z4c+KDjAegPyGYn5uVWmQFtEqKEF?=
 =?us-ascii?Q?jvsZqcHvaYM7w/SYrWFrnrnXANorrAZYffrCSxV/4k22s6Lb10/ptvl8W1nN?=
 =?us-ascii?Q?tXgKMkTcyaGtg9EgP5J9DBo7PskLfnzt9lwJwmpwun/o4s+FhmQ9T5RQZm3h?=
 =?us-ascii?Q?aoA+mw7AioYIr6ckdPCRa/2tdBMLGFdm+Uj1IFfeoI6jvlwxzk3Fk+Ke0l+3?=
 =?us-ascii?Q?USKi10KhdXNpjuMaI/1Y/nCH2eTL6Gth/FbQKAUqC2WvGTKKWcW04xwhQG4M?=
 =?us-ascii?Q?iA=3D=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-ID: <FAA48676A513FD4BB6BF117B09E525A9@namprd10.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: BL0PR10MB3011.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a96e3265-76fb-4548-00a3-08dadfa6be04
X-MS-Exchange-CrossTenant-originalarrivaltime: 16 Dec 2022 20:47:27.1376
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: mBWM20RDyeQQKlEoshJOjProCAffEi/0b2AmVpuplH0Vx5BdDNvpxH9wI5VT+EAsdYwqmYMXd/GDFCpyxynnYg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN0PR10MB5045
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1
 definitions=2022-12-16_14,2022-12-15_02,2022-06-22_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 bulkscore=0 malwarescore=0
 mlxscore=0 phishscore=0 adultscore=0 mlxlogscore=999 suspectscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000
 definitions=main-2212160184
X-Proofpoint-ORIG-GUID: _njVgPkq__DxKroYoEFqhjTXJax486wH
X-Proofpoint-GUID: _njVgPkq__DxKroYoEFqhjTXJax486wH
X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

* Andrew Morton <akpm@linux-foundation.org> [221216 14:01]:
> On Fri, 16 Dec 2022 18:53:15 +0000 Liam Howlett <liam.howlett@oracle.com>=
 wrote:
>=20
> > Mike Rapoport contacted me off-list with a regression in running criu.
> > Periodic tests fail with an RCU stall during execution.  Although rare,
> > it is possible to hit this with other uses so this patch should be
> > backported to fix the regression.
> >=20
> > An insufficient node was causing an out-of-bounds access on the node in
> > mas_leaf_max_gap().  The cause was the faulty detection of the new node
> > being a root node when overwriting many entries at the end of the tree.
> >=20
> > Fix the detection of a new root and ensure there is sufficient data
> > prior to entering the spanning rebalance loop.
> >=20
> > Add a testcase to the maple tree test suite for this issue.
>=20
> Shall do.
>=20
> > Cc: Andrei Vagin <avagin@gmail.com>
> > Cc: usama.anjum@collabora.com
> > Reported-by: Mike Rapoport <rppt@kernel.org>
> > Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
>=20
> I guess we want a cc:stable there?

Yes, please.  I'll be sure to do that in the future for backports.

>=20
> >  lib/test_maple_tree.c | 23 +++++++++++++++++++++++
>=20
> Belated review: all this code runs at __init time, so every dang
> function in there really should be marked __init, data marked
> __initdata, etc.  Like lib/test_bitmap.c.
>=20
> I wonder if there's some trick we can do external to the .c file to
> have the same effect.

This can be built as a module and also runs in userspace via
tools/testing/radix-tree.  I'm not sure about using __init in this
context but I'll look into it.

>=20
> Also, maple_tree_seed():set[] could be static ;).  So we don't have to
> initialize it at runtime.  Better would be static const.  Nitpick.

I'll have a look.  I'm sure there are more areas within my test code
that could be optimised like this.=