Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
CC:     Jeff Layton <jlayton@kernel.org>,
        Frank van der Linden <fllinden@amazon.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH] nfsd: don't use GFP_KERNEL from
 nfsd_getxattr()/nfsd_listxattr()
Thread-Topic: [PATCH] nfsd: don't use GFP_KERNEL from
 nfsd_getxattr()/nfsd_listxattr()
Thread-Index: AQHZb4qhR4jn7R6+a0evVV4Y3qmRcq8si0OA
Date:   Sat, 15 Apr 2023 16:13:22 +0000
Message-ID: <4BC7955B-40E4-4A43-B2D1-2E9302E84337@oracle.com>
References: <72bf692e-bb6b-c1f2-d1ba-3205ab649b43@I-love.SAKURA.ne.jp>
In-Reply-To: <72bf692e-bb6b-c1f2-d1ba-3205ab649b43@I-love.SAKURA.ne.jp>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?ueWu7yuMRqcsEQIUCtcRkF5HokLc+84pFMyxyogNlawySMVjc54DZBYdLx6B?=
 =?us-ascii?Q?2YI8WlY/Fb/jRiJuvPloPW6FlVD+yuR0PragPb/wTlAPXGHsyk8NiBHrbA1K?=
 =?us-ascii?Q?A6xdBiJo5TdGD2UEgZQouRLzH0llGX6a/5/MX4q/SUP2baEcQDuLfiJQbQ5Z?=
 =?us-ascii?Q?hx0x1vI2zhcV3RX4XdRwaN8KJ8E7SoXGT7dRs+iGw73LZA7ugz1+lIsiquzA?=
 =?us-ascii?Q?5ZAC3rKHWeCDHjC66KH5LOqvhP/LrZ1e/ERTDlJkh01ZSyayTRv6y+6MRTR4?=
 =?us-ascii?Q?Kd+x15TaSm56QVaA+dJqPJLQmTknfuDUHfCoDHcD6R1NTRLUx7qMMwvWrEXK?=
 =?us-ascii?Q?jIyS9cHR27ndrOA9ONsU/ycBaQ2SmjfbMlttNj/UhhHvE3eH5PmwdH93HXr7?=
 =?us-ascii?Q?iFU08jDl0P9aM/CAqzM1xM3JTwkNWDUnHwYDrEBWQPWvB/ilur/BAeq4CNto?=
 =?us-ascii?Q?KFY59mrqu0MiA9zYQdrxK8zD6gdy1oK2lik+6z2M7CvZ5tlOyB2Beju+0+Kz?=
 =?us-ascii?Q?URddrVC4w1yUXeQmThqQARBVJ4E+Z2m8GdK1dcVMYlAVE4lmVlzbM2IpA2Yk?=
 =?us-ascii?Q?aBEwnG20A9K/u/a8kSfJkizWrd4FFnzKAZD6M/rg8OuhB4ijhFEpfo8+pnWR?=
 =?us-ascii?Q?0OEMnB9qKDvxeqhnvCsxRaqwjM+R+pXNHE9ERhEn/PiG89GXecAjnR5iiChE?=
 =?us-ascii?Q?XlNvTHeB105WcQEaaY5GvSooZGsOpI7XxJWJMq7jWsdPPHB7gzLASPOdFsGS?=
 =?us-ascii?Q?kTfEQ4qqJGpxz7M1kfJcBMXKuUMYAk08SVInvdbROzwNROpBHkN2nd448DVx?=
 =?us-ascii?Q?YAVFAXBOMVz9dy2Yv5k6MnBJeAhcOC2hGcX+hmZQ0O1zfmYzWfGS+l1XpafO?=
 =?us-ascii?Q?2tODpf/+T9S3J/a9qt5h4eyyzUAMh7BwUFCXG8V3V7IXa56DdESoBUQK6SDZ?=
 =?us-ascii?Q?O1+aNnskQay1LfC1RSm62IcxB6bfDYYcqXFpGMq9DLNec7uo6RPYFK+pnGxc?=
 =?us-ascii?Q?0yAE6Z/uw3GPknkyZ8Ek4v4dKz1lV4dygub4RnPlh2baAtyuoJdpsUz5LGjq?=
 =?us-ascii?Q?3U1k73D+UxDs4pckTBTnOyt88dqxWHUw5B2LTQKcuaAGsV4XsR+QZKfPpQ1M?=
 =?us-ascii?Q?u3D7PETfS7gqAGn8kPmZOoT4q4U8bVmFTQZX3reWIZq2fjeVVvSE+jcD7NLz?=
 =?us-ascii?Q?XLz14YAz2IAEaFOSxaHCx8iSQYyL8WfN4ulZtpShpI33GL8OwODWMlIHY04k?=
 =?us-ascii?Q?QIsnlYWjMovCaCIn7QLsVxg959779CJZq2uYFMfMgVKYB2hATmbgsmG7jiHh?=
 =?us-ascii?Q?jpn8uNZQyBKVNEZ4JZIa20kViE7Cvjn4le+WSEpSvazROQH9bnteWgUjGbwc?=
 =?us-ascii?Q?LzeSWZ8Tu4IZ6ZRvZ+db/v66HONtUWMv7lQydAf/0TrbHC0JeO5/l0vicMES?=
 =?us-ascii?Q?tsxDLxArRrE00TzMInyVtWRG35FjvQlBvhCfFNx9cPikNaDcRPaoEVjPv46c?=
 =?us-ascii?Q?pmz5e3164NRia1ztiL3mKerS6JTGew/EqvzobYZbt8tucEvekw0EFDRCG7t4?=
 =?us-ascii?Q?vlvKbhgw/hVorSbxnVYqeLX1wfAvMNBykyEsqK3RBZtJ3UCSF5ykkLAJAEHy?=
 =?us-ascii?Q?ig=3D=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-ID: <8B758FDE992BA4438A6BF03E70D2B389@namprd10.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: BN0PR10MB5128.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: a897dd16-e335-4758-e010-08db3dcc5590
X-MS-Exchange-CrossTenant-originalarrivaltime: 15 Apr 2023 16:13:22.0904
 (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: iSuqxrRCEU4LRPtXVCGRXhu6Pc2vRh4f0/G/x133rZv1Epuazqy8gdaM6Y8oa56XepCvdxVwfxQkFnZtkbHW4g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR10MB6225
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22
 definitions=2023-04-15_07,2023-04-14_01,2023-02-09_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 spamscore=0
 adultscore=0 malwarescore=0 bulkscore=0 suspectscore=0 mlxscore=0
 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2303200000 definitions=main-2304150150
X-Proofpoint-GUID: alMYYhXnsauN7uVtO89RgEl9Z113LfMU
X-Proofpoint-ORIG-GUID: alMYYhXnsauN7uVtO89RgEl9Z113LfMU
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-nfs.vger.kernel.org>
X-Mailing-List: linux-nfs@vger.kernel.org


> On Apr 15, 2023, at 7:07 AM, Tetsuo Handa <penguin-kernel@I-love.SAKURA.n=
e.jp> wrote:
>=20
> Since GFP_KERNEL is GFP_NOFS | __GFP_FS, usage like GFP_KERNEL | GFP_NOFS
> does not make sense. Drop __GFP_FS flag in order to avoid deadlock.

The server side threads run in process context. GFP_KERNEL
is safe to use here -- as Jeff said, this code is not in
the server's reclaim path. Plenty of other call sites in
the NFS server code use GFP_KERNEL.

But I agree that the flag combination doesn't make sense.
Maybe drop GFP_NOFS instead and call it only a clean-up?


> Fixes: 32119446bb65 ("nfsd: define xattr functions to call into their vfs=
 counterparts")
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
> fs/nfsd/vfs.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>=20
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 5783209f17fc..109b31246666 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -2164,7 +2164,7 @@ nfsd_getxattr(struct svc_rqst *rqstp, struct svc_fh=
 *fhp, char *name,
> goto out;
> }
>=20
> - buf =3D kvmalloc(len, GFP_KERNEL | GFP_NOFS);
> + buf =3D kvmalloc(len, GFP_NOFS);
> if (buf =3D=3D NULL) {
> err =3D nfserr_jukebox;
> goto out;
> @@ -2230,7 +2230,7 @@ nfsd_listxattr(struct svc_rqst *rqstp, struct svc_f=
h *fhp, char **bufp,
> /*
> * We're holding i_rwsem - use GFP_NOFS.
> */
> - buf =3D kvmalloc(len, GFP_KERNEL | GFP_NOFS);
> + buf =3D kvmalloc(len, GFP_NOFS);
> if (buf =3D=3D NULL) {
> err =3D nfserr_jukebox;
> goto out;


--
Chuck Lever