Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
To:     Naohiro Aota <Naohiro.Aota@wdc.com>
CC:     Eryu Guan <guan@eryu.me>,
        "fstests@vger.kernel.org" <fstests@vger.kernel.org>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
        "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
        "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
        Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH v3 1/6] common/rc: fix btrfs mixed mode usage in
 _scratch_mkfs_sized
Thread-Topic: [PATCH v3 1/6] common/rc: fix btrfs mixed mode usage in
 _scratch_mkfs_sized
Thread-Index: AQHYJJmku29ruJf1Uk6KIJBch9qCEaycrX+AgADrSQCAAEMrAA==
Date:   Mon, 21 Feb 2022 11:02:55 +0000
Message-ID: <20220221110254.y2yb7xdlf22ahh7k@shindev>
References: <20220218073156.2179803-1-shinichiro.kawasaki@wdc.com>
 <20220218073156.2179803-2-shinichiro.kawasaki@wdc.com>
 <YhJzp/dnfixk/nMn@desktop> <20220221070229.2hs45fqk7fbfbgpk@naota-xeon>
In-Reply-To: <20220221070229.2hs45fqk7fbfbgpk@naota-xeon>
Accept-Language: en-US
Content-Language: en-US
wdcipoutbound: EOP-TRUE
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?UEPS2sCL2ZqoLZU910zDjjliw8GNabw3JoAXaBtCt7TMdUq6zx1TMT2v7iBi?=
 =?us-ascii?Q?MNIx05wqM0UNYFHEEiOo2DfqjLhV5MMCnRvm/t0FzcahN2IK5BQE0N0otJPU?=
 =?us-ascii?Q?dOdWg+VmjQfTyUrrbR0gld09WaBoZ6G6g+P9XjoJYRIS+PHTzusf8KWc53Qj?=
 =?us-ascii?Q?iKAoCr8Jj6c2zOKsEqqVoYmo8KMKoWg8wLZIgoxDsvwyi0UbBKbMR9kurK8F?=
 =?us-ascii?Q?gzYNbxb1+9QHskHZZQ1a9sxN3mQCYxXVQ+Ef8zHynpCRGGczkPiHwcK6XkTM?=
 =?us-ascii?Q?o5Zc1t0Nm4aKR6Ki5Z5UoLgPVjCo7cD/UPbDn6wC8LPTu4WF5j0SKR2leYhR?=
 =?us-ascii?Q?uGkvn1c8/PUF9t6Y1QLTO6zrnWYiZcTb2P1HonYdZwqOYjUjdil/eu8AHfr3?=
 =?us-ascii?Q?DZOPO7WUvMpWGSWVyC7m1+Vk3y5mEV+bI4xucnjsnm4FS4kcEDId+JU1/XtD?=
 =?us-ascii?Q?q1C8hNzNIhhWz8oNP3LzakDyOiFO/Hg9ngoe/BLWg7hMhIJa0pot6+M98s8h?=
 =?us-ascii?Q?pI5PhBNI3DnrkYQq1b0jQR1bjSN/PDCFwD2ea9wkFsvKbaUKkBvL37n08ywk?=
 =?us-ascii?Q?7V7kOMztPTLYeyQX5wgQ4gCF/xB8RYalgKVkxcJcE23WNEC3Yt88HI4/p5a2?=
 =?us-ascii?Q?ay3x0sHeXpHrPb5V+C7iNcwGZOWK5bIAUpZub2qAyhh5V1O2N7m1nsMcNJ57?=
 =?us-ascii?Q?ipDz9S+U6Nr0OWDiadNlbIvBiW3g4CUhqoQFmRnxlYz4BKPWTLM/I6keQTP3?=
 =?us-ascii?Q?5Om9oflsk9dvrYBvx0ZL99ntOOHN+QcxwXLHrmwiwq63OzqEtE1kN9iKnS5W?=
 =?us-ascii?Q?xGBHnt02h9bKoPtMeUNZIFgTHPkCN4MRsuuI6wcltpMI6VjreN0XYT/jU59u?=
 =?us-ascii?Q?gSDOE76ozIvoJ3tVBUYSwMAKCbsSo2RiDzAiIRJabNpxDd1G2AYG4yQDZtHE?=
 =?us-ascii?Q?npOcCwgw8wXe+9tDL8QQbF2HmpeOk1TutM02+9CZmQnNNKeCbdUHSTzrtNgb?=
 =?us-ascii?Q?vukTEYs6Dhg+uWr7pglaCVRGoybwAX6rbGnkDVnnkjoICWbVZaUziY9RdOaA?=
 =?us-ascii?Q?YybWSLnQU7QQnQkyS9uLQE0gKMvQNjNpLepQdbiSfeNN1OqZgkWv/UwvzGrI?=
 =?us-ascii?Q?dtQs+6B0h4omEA+adu4NpZ7tL17LQY5rq5QcnGbbuO9E8UgD0fYLy/q9BGJP?=
 =?us-ascii?Q?+KV98dgMlukT0FWSVzSx4r66olNfyewrxD8kcJjnzE1e36gsWaqkalW9FR8y?=
 =?us-ascii?Q?wepjnpIxwRIdcK9KhVBhPjGq3VbYpt7100+B3v+y8s9I15WbWKCSGIW2DQUn?=
 =?us-ascii?Q?qWQ3xGf9GnyEzaLIRpfxLt7EPQOXYdqIcC9xbKQFhMCwIwYSB+B0id+vMeOV?=
 =?us-ascii?Q?cvSLBX0C5ptG42nU78oShXka78W1BlR9MfMQVD4H0+lW9JmJ4c3QX/BAuk2f?=
 =?us-ascii?Q?BX4CyY3zWcdF2eeoFvF8m0SZQBRHDfAuMZ/F32Eze/gIFicic5S4JoQpJpXl?=
 =?us-ascii?Q?0V2eZjguLhtW6PtZ81seuoW4Usxs327aUoHOrARWBJM5rhRSgumxtsMpJ4E1?=
 =?us-ascii?Q?8U7ys25Z/zOKJUZm5NQlY2bW0fqLLyswIlesnnUq/6dbd8sVo9RWPSMAwjM/?=
 =?us-ascii?Q?Z368rZsVIo4FVg08w+0upsti2j7EGGxnnz5driruwN+bjjl5IK8T4UdCSrta?=
 =?us-ascii?Q?IfYtpj7asQT+dMNcRvkryXQkV0s=3D?=
Content-Type: text/plain; charset="us-ascii"
Content-ID: <FB7B9428D9250048B8B372F51265DDE0@namprd04.prod.outlook.com>
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-OriginatorOrg: wdc.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: DM8PR04MB8037.namprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 0b54bfb6-9731-48ef-ade7-08d9f529b667
X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Feb 2022 11:02:55.1097
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: q8mKjyAOna3plLaCyDI+MPwp0NX4R1n9eZ9xwqcGCeCknedEqj3Mni0x+lDcpRJwbW4eye2G8Rb8yvkDc0Cnqa5+pPNsR5OpFnP/xp0OSHE=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN3PR04MB2354
X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,
        SPF_NONE,T_SCC_BODY_TEXT_LINE 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-ext4.vger.kernel.org>
X-Mailing-List: linux-ext4@vger.kernel.org

On Feb 21, 2022 / 07:02, Naohiro Aota wrote:
> On Mon, Feb 21, 2022 at 01:00:23AM +0800, Eryu Guan wrote:
> > On Fri, Feb 18, 2022 at 04:31:51PM +0900, Shin'ichiro Kawasaki wrote:
> > > The helper function _scratch_mkfs_sized needs a couple of improvement=
s
> > > for btrfs. At first, the function adds --mixed option to mkfs.btrfs w=
hen
> > > the filesystem size is smaller then 256MiB, but this threshold is no
> > > longer correct and it should be 109MiB. Secondly, the --mixed option
> >=20
> > I'm wondering if this 256M -> 109M change was made just recently or was
> > made on old kernel.
>=20
> The check is imposed from the userland tool btrfs-progs. The value is
> calculated from a code in 31d228a2eb98 ("btrfs-progs: mkfs: Enhance
> minimal device size calculation to fix mkfs failure on small file"),
> which is released around v4.14.
>=20
> But, after rechecking the code, the size part of the patch looks
> invalid to me. My bad.
>=20
> https://github.com/kdave/btrfs-progs/blob/master/mkfs/common.c#L651
>=20
> As said in 50c1905c2795 ("btrfs: _scratch_mkfs_sized fix min size
> without mixed option"), we need to consider every possible profile to
> decide the minimal value.
>=20
> That gives me:
>=20
> - reserved +=3D BTRFS_BLOCK_RESERVED_1M_FOR_SUPER +
> 	    BTRFS_MKFS_SYSTEM_GROUP_SIZE + SZ_8M * 2;
>   --> reserved =3D 1M + 4M + 8M * 2 =3D 21M
>=20
> - meta_size =3D SZ_8M + SZ_32M;
> - meta_size *=3D 2;
> - reserved +=3D meta_size;
>   --> reserved =3D 21M + (8M + 32M) * 2 =3D 101M
>=20
> - data_size =3D 64M;
> - data_size *=3D 2;
> - reserved +=3D data_size;
>   --> reserved =3D 101M + 64M * 2 =3D 229M
>=20
> We can also confirm the calculation with a zero size file:
>=20
>    $ mkfs.btrfs -f -d DUP -m DUP btrfs.img
>    btrfs-progs v5.16=20
>    See http://btrfs.wiki.kernel.org for more information.
>   =20
>    ERROR: 'btrfs.img' is too small to make a usable filesystem
>    ERROR: minimum size for each btrfs device is 240123904
>=20
> So, the original 256MB is roughly correct.

Naohiro, thank you for checking the detail. I agree that we should keep the
number 256MB. I will drop that part and repost the patch.

--=20
Best Regards,
Shin'ichiro Kawasaki=