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Fri, 14 Feb 2020 08:53:40 +0000 From: Johannes Thumshirn To: Qu Wenruo , "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH v2 1/3] btrfs: backref: Introduce the skeleton of btrfs_backref_iterator Thread-Topic: [PATCH v2 1/3] btrfs: backref: Introduce the skeleton of btrfs_backref_iterator Thread-Index: AQHV4w7AawHM4rC3gku58k/EoZpqqQ== Date: Fri, 14 Feb 2020 08:53:40 +0000 Message-ID: References: <20200214081354.56605-1-wqu@suse.com> <20200214081354.56605-2-wqu@suse.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Johannes.Thumshirn@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: b70b15bf-69a3-4d65-b2aa-08d7b12b633b x-ms-traffictypediagnostic: SN4PR0401MB3519: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:8273; x-forefront-prvs: 03137AC81E x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(4636009)(346002)(39860400002)(366004)(376002)(136003)(396003)(199004)(189003)(5660300002)(91956017)(76116006)(86362001)(316002)(4744005)(33656002)(52536014)(9686003)(6506007)(64756008)(66946007)(66556008)(55016002)(66476007)(71200400001)(66446008)(53546011)(8676002)(7696005)(81166006)(2906002)(81156014)(186003)(26005)(110136005)(8936002)(478600001);DIR:OUT;SFP:1102;SCL:1;SRVR:SN4PR0401MB3519;H:SN4PR0401MB3598.namprd04.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: MEG+1nhVwW7jLsKdwPEzJxPmp6Y4MtP4ACXaZ0++EPJfRguvH9AbrhGUX49ur0DqR0X8y2aiDe35Z6vY6wweKnsFq1rna7C54XcE87lqHI/gcGOC+exD/3aomeJDQL13bNGZyDkJo75j48Ea4mysNHLsDAUX/PsFurIkiBOTF/1n5Cu+L9XJq5u/DvpOopUEk/dzvzTBu+wxU8AsWqlF76vIUHvdeCLhSYO/UiMHR+3xwv4z0UrrMn5EdoOJ6eudtjZfmlswkvRB5vvLyGARNEkdDbitel9ZB0atKK2BjuloFDSoO+RfDodprK0Nj5L2f7gWtN+P0Q6Zwoul5F/H2otobuig52HDaODjnOOsvSlE2FMy6hphJF+DWhSSMbieQPo+aIdi8VPlTXwUW1zTbrKmTNWt9ACnMbEWQqvWcKDYyFkWeY7o2TLRjCKPXKXa x-ms-exchange-antispam-messagedata: gwZlcDk6/pJ3YVORnuYe2Rm9xwZLlZCmZgYlcNHhfOv8ONbt2bFlS+Sv7wdnwr74hdXM1On0SOVzrIgiRcfaRskafulCxtzd5voq0w4RnRiyVZrgMAbZTNj3FL8lvKoijNexHxHoBbn+yyMZKvkIHw== x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: b70b15bf-69a3-4d65-b2aa-08d7b12b633b X-MS-Exchange-CrossTenant-originalarrivaltime: 14 Feb 2020 08:53:40.1572 (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: 8q7wOC8ynSBZ+D5vL7/Korm1LUOrJIQYDzuzR3R77JAhL4rbiNelLovxAQ++qwghGqt6l6jP+e78IpRDIOaxDnm9EULjYDBTDdfdxsinEkE= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN4PR0401MB3519 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 14/02/2020 09:14, Qu Wenruo wrote:=0A= > Due to the complex nature of btrfs extent tree, when we want to iterate= =0A= > all backrefs of one extent, it involves quite a lot of works, like=0A= Nit: work ^=0A= =0A= > search the EXTENT_ITEM/METADATA_ITEM, iteration through inline and keyed= =0A= ^ searching I think but a native English speaker might want to double = =0A= check on that.=0A= =0A= [...]=0A= =0A= > The idea of btrfs_backref_iterator is to avoid such complex and hard to= =0A= > read code structure, but something like the following:=0A= > =0A= > iterator =3D btrfs_backref_iterator_alloc();=0A= > ret =3D btrfs_backref_iterator_start(iterator, bytenr);=0A= > if (ret < 0)=0A= > goto out;=0A= > for (; ; ret =3D btrfs_backref_iterator_next(iterator)) {=0A= > /* REAL WORK HERE */=0A= > }=0A= > out:=0A= > btrfs_backref_iterator_free(iterator);=0A= =0A= =0A= I personally like for each style macros to wrap these a lot, but seeing =0A= the loop is only used once in your patchset I'm not sure it's worth =0A= adding it.=0A=