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Mon, 25 May 2020 11:44:06 +0000 From: Johannes Thumshirn To: "dsterba@suse.cz" CC: Johannes Thumshirn , "linux-fsdevel@vger.kernel.org" , "linux-btrfs@vger.kernel.org" , Eric Biggers , Richard Weinberger , Jonathan Corbet Subject: Re: [PATCH v3 3/3] btrfs: document btrfs authentication Thread-Topic: [PATCH v3 3/3] btrfs: document btrfs authentication Thread-Index: AQHWKdGHpFk4qUNYxkaDbw38lHwpUg== Date: Mon, 25 May 2020 11:44:06 +0000 Message-ID: References: <20200514092415.5389-1-jth@kernel.org> <20200514092415.5389-4-jth@kernel.org> <20200524195513.GN18421@twin.jikos.cz> <20200525112622.GP18421@suse.cz> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: suse.cz; dkim=none (message not signed) header.d=none;suse.cz; dmarc=none action=none header.from=wdc.com; x-originating-ip: [129.253.240.72] x-ms-publictraffictype: Email x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 9a32661a-2934-4b8b-f228-08d800a0ee3d x-ms-traffictypediagnostic: SN4PR0401MB3662: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:8882; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9a32661a-2934-4b8b-f228-08d800a0ee3d X-MS-Exchange-CrossTenant-originalarrivaltime: 25 May 2020 11:44:06.3300 (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: M/sHU8jooHnbfEpWup3OZGKGfiksahrOdFEge0T6cHgVfefKWlZ6qSkrsCFEI0p5TZTzLVEQ82xFnovUpQ+ZgRakxroV+6WBK1lKuVpxBLE= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN4PR0401MB3662 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 25/05/2020 13:27, David Sterba wrote:=0A= >>> Suggested fix is to have a data block "header", with similar contents a= s=0A= >>> the metadata blocks, eg.=0A= >>>=0A= >>> struct btrfs_hash_header {=0A= >>> u8 fsid[BTRFS_FSID_SIZE];=0A= >>> u8 chunk_tree_uuid[BTRFS_UUID_SIZE];=0A= >>> __le64 generation;=0A= >>> };=0A= >>>=0A= >>> Perhaps also with some extra item for future extensions, set to zeros= =0A= >>> for now.=0A= >>=0A= >> This addition would be possible, yes. But if we'd add this header to eve= ry=0A= >> checksum in the checksum tree it would be an incompatible on-disk format= =0A= >> change.=0A= > =0A= > No. It's only in-memory and is built from known pieces of information=0A= > exactly to avoid storing it on disk.=0A= > =0A= =0A= Ah OK, now I get what you meant. This should then be only for the authentic= ated =0A= FS I guess.=0A= =0A=