From:   Nadav Amit <namit@vmware.com>
To:     Peter Xu <peterx@redhat.com>
CC:     Axel Rasmussen <axelrasmussen@google.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.cz>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Matthew Wilcox <willy@infradead.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@kernel.org>,
        Muchun Song <muchun.song@linux.dev>,
        Shuah Khan <shuah@kernel.org>,
        James Houghton <jthoughton@google.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH v3 2/5] mm: userfaultfd: don't pass around both mm and vma
Thread-Topic: [PATCH v3 2/5] mm: userfaultfd: don't pass around both mm and
 vma
Thread-Index: AQHZUH4VuXC6ip2bZEW9WDQchYsNXa7ugECAgAALUYA=
Date:   Tue, 7 Mar 2023 01:44:05 +0000
Message-ID: <54D49E2C-F2EF-4C1E-AFE9-FD742CEA33EB@vmware.com>
References: <20230306225024.264858-1-axelrasmussen@google.com>
 <20230306225024.264858-3-axelrasmussen@google.com> <ZAaNXTXs5ey4QYTl@x1n>
In-Reply-To: <ZAaNXTXs5ey4QYTl@x1n>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?utf-8?B?TUMybzFUdU83RHpKU1A2RnM1NWhpcGtTemd3Rk1ybDlsbXhOZFREZmJMTGw3?=
 =?utf-8?B?OWxvZmJvS1JrRnV2clZhT0hiVnArc0xHZ0g0R0hkVlBKQUpMbFRDbWVnUXFD?=
 =?utf-8?B?MXNNZzkvdWxQVUloUmhWVFhlR0VHSy95OUdBNmsvSkxvTFovN3lXeWxLY0Jm?=
 =?utf-8?B?cDJxeGN5Ykc2Szk4LzM1YUZCZk8xcDdpbG56WnBxZWlicldCcGhyaVBOUFhv?=
 =?utf-8?B?UnlwU01hOWRKZ2VBalBTWERzbXc0NE9RMHhkREFSY04vYjZGN0FJeHpyQTd6?=
 =?utf-8?B?REZYYXZta002azBqdCtaYVdXVVRzMEZRTGhqNFdNOWxFb2ZkOUdMNHo3d1M2?=
 =?utf-8?B?bC9ycmQ4U3FvQ1YzbGkzWjJWOUVsRGhWTU44N1pBS3VsY013Tm5KeVVaeWVN?=
 =?utf-8?B?NzVWbjlIbE9wSW16SGVFNjBZSWZKVjN2TWhkR2NRbVFyNU1iVi9QckNRU3Fa?=
 =?utf-8?B?V1AyazY4RmJ2TjRLY292TnVFc2tJOFVxTHZMMTJ1b21kOXAwNlFGNWVmYWlB?=
 =?utf-8?B?eTFSVTM2RHlmN2dBSlZsWlJtallPRFdSMHhTWTV5bEdmMkVJSGloOTlFWU1x?=
 =?utf-8?B?MmJuckczMVZWT2cybnBvdExHaXNjS2pyNFhNTDk5UWt2cVU3a1B0NkdXcE5Z?=
 =?utf-8?B?QzFGLzIvRWY4K3ZIakFPSlBnS0tEZWlPUDVMRkN1NG95eFhCYVVCcUdWZzlQ?=
 =?utf-8?B?aGJuSHl5L1BQMHRPMnA0SU9FYkdCaVBSOERQSElWa1dvQm1LM2NoV3J1d0JZ?=
 =?utf-8?B?NUJaa2Q0MXpta0o3SDdMWEZaWkZJL1czTzNDaWJOczJVV0EzM2lMVDAyb24x?=
 =?utf-8?B?K3N4aTRxMEt3Z2xnYTlRY2JXaW5CelRHcXVHUzFETkE0K1B5bFBFVjBESVor?=
 =?utf-8?B?TldoWklXcVUydU15czIrZHR1VmNaU0swMjVRREl3NG9Ea3lwWWRtY3QwK3dH?=
 =?utf-8?B?QzczZFU2TnVIbHFXcERrdmhKTm16M1E1OFNzMG9HWXdMbjFJTWY0Y1ovWDFK?=
 =?utf-8?B?eWNQNGZpc1FMWnpFbmsrTnlPZFJCSUJUd2llaHlDL0lCQWp5MEc3dmk5ejg0?=
 =?utf-8?B?cGY2eWV2TDNwL1hLaHpGTkY5SE8vZlRBbExmemFYelhFSG9XMXNJS3pra08z?=
 =?utf-8?B?MklON3JyMFVLWnp5VjJ4T2tGWVVTVkl2ZDF4MUNSUTU5eG5waS9qcUtKRGhM?=
 =?utf-8?B?TmxtUHFxT3BpTlZuSDZualdyN3puSC95TlZ4VDU0SG5SbUR5VHlJL3gybDMv?=
 =?utf-8?B?RUl5K21OSldpNStRS3BkNDJDLy9oMUpNZGhMWGZ6T1BNVlpmb3ZmVWhnbjc0?=
 =?utf-8?B?aDZBRkRZSlZPei80b3RMTDFadngvM0ZYZERBeGQ4dFREdWs2emxkTkRYSVpV?=
 =?utf-8?B?czJNM3lEOFRHL1AzYlhMdnV0aWUyeXFiWlVVUytqZWEyMWh0QllIeW9ybUw1?=
 =?utf-8?B?U3VKZXVFakp3Q25GV05ncENMbVhpeHo5QjJ3b1VoQkd3VDRrcXpEM2VnQklW?=
 =?utf-8?B?ODE2aEM5ajI1MFVNc2lDSEF1TzhsNGpjTHJDbWNhNUtTbW1DMXhmVWtISTc4?=
 =?utf-8?B?SXBaQzBwbTN1OThGKzV3MFZhMlVuWmkvTWpGcFJFT0JQLzlHV0RhK1EzT0Vv?=
 =?utf-8?B?VHpKRXVrWVJZZmwvdnNEYUFxNWx2d0ZuR3I3a3FURDVEL3BnNloxNDcySWQ1?=
 =?utf-8?B?VGRhSExZMEJXaCt2OXgwWHQyTG9JK1I0dHVBendpZWIxbmNJa3NXc2kvQStq?=
 =?utf-8?B?dE5iZGpFOERsbzRJN3lISFJRZmkvUlBiSFFaZzZObkdSYTNWU3JrTjh0RElD?=
 =?utf-8?B?NHl6WkdBUmVKQVlVKzk0NHV5S2xEbXV5bGorZEU0OGRNZFVYR2x6Nk5wQ29F?=
 =?utf-8?B?ZGVESmVtVFEzYUdJb2dDSGpxbVliWUlvNWVIK0hPNTUwOXd6SkJmVXYrczJm?=
 =?utf-8?B?dWZxQmhLak91Sk1MWTJRcDZBcWgrMTFLUjhpTmt0SElwVG10YThzNWQ5cjhT?=
 =?utf-8?B?QzZTOC8vWHEvSGxrMWlLcThYMDZjdThCV1BCcTl6eEZVY0NVM3BsQ202VGRn?=
 =?utf-8?B?RitZQVMvNGN5M3FOdzRnNGdDTUJCanNWNU9mWE1tRTBBd0hSUWhKc2ErR0R4?=
 =?utf-8?Q?M6duhFZ1ieJKseGGQZNbu+1ud?=
Content-Type: text/plain; charset="utf-8"
Content-ID: <71D342F4B4066D4B8DA8AD776FDEF529@namprd05.prod.outlook.com>
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-OriginatorOrg: vmware.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: BY3PR05MB8531.namprd05.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 7c2fe1b9-1985-4c66-0eed-08db1ead6fc8
X-MS-Exchange-CrossTenant-originalarrivaltime: 07 Mar 2023 01:44:05.6458
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b39138ca-3cee-4b4a-a4d6-cd83d9dd62f0
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: uTognryjdjEjswYSUKvxJ1ucbWVbCTyCRGm3Sb/ozSiGEeDMlPLlmV1C6HA3rmKC96u2u2wM5s+QY/AmQsKU6Q==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR05MB3285
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
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