Received-SPF: pass (google.com: domain of linux-kernel+bounces-64156-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Tue, 13 Feb 2024 14:21:31 -0500
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>, akpm@linux-foundation.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, selinux@vger.kernel.org,
        kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com,
        david@redhat.com, axelrasmussen@google.com, bgeffon@google.com,
        willy@infradead.org, jannh@google.com, kaleshsingh@google.com,
        ngeoffray@google.com, timmurray@google.com, rppt@kernel.org
Subject: Re: [PATCH v5 3/3] userfaultfd: use per-vma locks in userfaultfd
 operations
Message-ID: <20240213192131.wgr7htg7crhmrsl3@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Lokesh Gidra <lokeshgidra@google.com>, akpm@linux-foundation.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, selinux@vger.kernel.org,
	kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com,
	david@redhat.com, axelrasmussen@google.com, bgeffon@google.com,
	willy@infradead.org, jannh@google.com, kaleshsingh@google.com,
	ngeoffray@google.com, timmurray@google.com, rppt@kernel.org
References: <20240213001920.3551772-1-lokeshgidra@google.com>
 <20240213001920.3551772-4-lokeshgidra@google.com>
 <20240213033307.zbhrpjigco7vl56z@revolver>
 <CA+EESO5TNubw4vi08P6BO-4XKTLNVeNfjM92ieZJTd_oJt9Ygw@mail.gmail.com>
 <20240213170609.s3queephdyxzrz7j@revolver>
 <CA+EESO5URPpJj35-jQy+Lrp1EtKms8r1ri2ZY3ZOpsSJU+CScw@mail.gmail.com>
 <CAJuCfpFXWJovv6G4ou2nK2W1D2-JGb5Hw8m77-pOq4Rh24-q9A@mail.gmail.com>
 <20240213184905.tp4i2ifbglfzlwi6@revolver>
 <CAJuCfpG+8uypn3Mw0GNBj0TUM51gaSdAnGZB-RE4HdJs7dKb0A@mail.gmail.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAJuCfpG+8uypn3Mw0GNBj0TUM51gaSdAnGZB-RE4HdJs7dKb0A@mail.gmail.com>
User-Agent: NeoMutt/20220429
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: 
	=?us-ascii?Q?fB09WlAMHpcLB5BdTUa4uGFQq3QE0FxN7asgLbx/4Z5yTUMVM1ytcFAIOnEj?=
 =?us-ascii?Q?zskLnVHugfV2mzWRpZ5rPZ7WxkHOI+stncIMOKYy7BoBBj03Is25x8PFcptt?=
 =?us-ascii?Q?TIDEwU0xpa7qvmvWmY0mq7tLD/nRC/Q8Tw2dfHyewWmRiO1ag8cLT4ybj0BD?=
 =?us-ascii?Q?EzvBh3Q40LS+ccj1oJYOZiUC8lVWmlvayv906MQuDMduYBJVG2qoKdZpPNe8?=
 =?us-ascii?Q?ec5fgTmrtxtcaad1l01Pqed9xkyA6lkl9IXSBH0DjcCo4ydllKtpLj7NPuCQ?=
 =?us-ascii?Q?+ulR3ghLaAmV3mwJ+sHBAd567AzX8GkFxG5dP7WIuwYqZHS4JOVLz/+Y0etW?=
 =?us-ascii?Q?CzzXOaU7U6t72yBXBUWSzQ9ijxfkSyRlGOF+t8nRTP+ieGdIzgfza/VM8tqN?=
 =?us-ascii?Q?4GyQeZetg8VOgXgTN0dBt2+H6i8jRjnCROouzOCLF6JV9J45Egmq7nFhZ696?=
 =?us-ascii?Q?eQSZ/QgwXSceLYPwq5vpzO65oJFkiGjjQJ2JiFb2twc4McWyLZBYQdJHmID/?=
 =?us-ascii?Q?2u02O+h2xFSRg5XCU9g8QmgNDRIWveRraV93jbVAISfUoM1RVQgDl0BRXzAY?=
 =?us-ascii?Q?bSsYH9OBUQ4FWhq9SIA9QShzRu6ak9fa008wUTfLWsLzMv/QlIwmVCHkWteN?=
 =?us-ascii?Q?6fsndIeN2h3v2ZHf7PGUgHYxl1ffggDkeHdbpmKaTgUCPakJNF84W2V4JetN?=
 =?us-ascii?Q?xCbkoox4e/Q8dKxmwmfXLqYh1S9ztWLz3VlRgy1jLdpVky3zJH0bE5czVLXA?=
 =?us-ascii?Q?oocf0zUWccBR/JRiZTuBpeJrMqJQgZtPBzz3e4Kwt2DTH9P1vp+fZWBDSKGo?=
 =?us-ascii?Q?L3K3c49gAHI22LioYuwojnTnI8RkWTT+0sASpXKDhTAR2LncrIFDsMwOQhW3?=
 =?us-ascii?Q?7GJCi8RIi86AFQsCWjtHfI++o2yma+UaDgWJLweNaWIFITRROqDBL6ORdTD+?=
 =?us-ascii?Q?sSMYep5q1bGIc6dR2JjhST0tml7A4ypCYZ/dXKFc8XZ+OwkuNxLKANPV8gi4?=
 =?us-ascii?Q?J9xy4Xv0PfSxwE+BvMaJeg0/Xw6gh+omYXWpkPZUKU6YTLhDTR1bX//lTQ1k?=
 =?us-ascii?Q?SaxT87x8ViIrsbY8DboLiLQhNx/y7FWlHL0gY6kclbsvKAb6PmNg0KqiRAS+?=
 =?us-ascii?Q?ztzd41c6bKiVtEqLWC5ORNzaS4vvIpgzkmnledBrRyrhlTZjHgVrJNpkKoPi?=
 =?us-ascii?Q?6MOKIp2n+mwQJlEW4WjbDWBdZXRttzwsKymDc70oPGDDpLg/tUd+E36/8to1?=
 =?us-ascii?Q?oAXpcj0IWXkLiAwK2FOXuJyKT3SzLTZXZJwAJr1X+/sxd6lv3EWPsMotO/FL?=
 =?us-ascii?Q?l0Cm/WTlBOGkTvabR2gI100iMv+mS40hG8tO6i09V5xwTeNg2imKAdAGOQrO?=
 =?us-ascii?Q?/qAfDLDUmS+lMzA2ZS2W8RLvUGUYnlnx3eX0jTq1z7Dd9hAoYuk2hwYEaLwL?=
 =?us-ascii?Q?GdeeRDOqRbEbL9KZnlxrnJ5CdlGmGmXvM/609+Pq6928ZE37OYyQ51CWPmkr?=
 =?us-ascii?Q?AD8CsQ9CwCQxLcvO3DlVec4tYfDiYme5KnotDCVTjZ0DnAPd1cfOfjnepyjp?=
 =?us-ascii?Q?VoSnKnPP0DExJSHJDb2r3oVI2ZvgZrRdW09z85Db?=
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-Network-Message-Id: 69878155-707e-4a80-3e5a-08dc2cc8fd7e
X-MS-Exchange-CrossTenant-AuthSource: DS0PR10MB7933.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Feb 2024 19:21:33.8763
 (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: tpLKzcpRFETHBScQ3RQO3okc/3Uxk1dEQj5d8a0eYOvn1Lck6UV4pyLVGFS+LqmXqFwKH4tlYtFhAzo23PM5Xw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR10MB7718
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2024-02-13_12,2024-02-12_03,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 bulkscore=0 suspectscore=0
 phishscore=0 adultscore=0 spamscore=0 mlxlogscore=735 malwarescore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311290000
 definitions=main-2402130153
X-Proofpoint-ORIG-GUID: YIXqzCdfABWKlZRT57DFssJtAQXMewo8
X-Proofpoint-GUID: YIXqzCdfABWKlZRT57DFssJtAQXMewo8

* Suren Baghdasaryan <surenb@google.com> [240213 13:57]:
..

> >
> > Yes, I don't think we should be locking the mm in lock_vma(), as it
> > makes things hard to follow.
> >
> > We could use something like uffd_prepare(), uffd_complete() but I
> > thought of those names rather late in the cycle, but I've already caused
> > many iterations of this patch set and that clean up didn't seem as vital
> > as simplicity and clarity of the locking code.
> 
> Maybe lock_vma_for_uffd()/unlock_vma_for_uffd()? Whatever name is
> better I'm fine with it but all these #ifdef's sprinkled around don't
> contribute to the readability.

The issue I have is the vma in the name - we're not doing anything to
the vma when we mmap_lock.

> Anyway, I don't see this as a blocker, just nice to have.

Yes, that's how I see it as well.