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Thu, 28 Jan 2021 10:51:57 +0000 Received: from VI1PR0401MB2382.eurprd04.prod.outlook.com ([fe80::9c:2015:e996:e28]) by VI1PR0401MB2382.eurprd04.prod.outlook.com ([fe80::9c:2015:e996:e28%11]) with mapi id 15.20.3784.019; Thu, 28 Jan 2021 10:51:56 +0000 Subject: Re: [PATCH v5 00/18] btrfs: add read-only support for subpage sector size To: dsterba@suse.cz, Qu Wenruo , Josef Bacik , linux-btrfs@vger.kernel.org References: <20210126083402.142577-1-wqu@suse.com> <20210128103452.GG1993@twin.jikos.cz> From: Qu Wenruo Message-ID: <4e3811e2-a639-fc40-390e-afe9efef0e29@suse.com> Date: Thu, 28 Jan 2021 18:51:46 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20210128103452.GG1993@twin.jikos.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Originating-IP: [149.28.201.231] X-ClientProxiedBy: PH0PR07CA0088.namprd07.prod.outlook.com (2603:10b6:510:f::33) To VI1PR0401MB2382.eurprd04.prod.outlook.com (2603:10a6:800:23::23) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [0.0.0.0] (149.28.201.231) by PH0PR07CA0088.namprd07.prod.outlook.com (2603:10b6:510:f::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.17 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?J/yWPkpnshZxpVB+b9zJGDYmeUdwwLMLlLiwC11/DCSs82RJF63OtCXok64R?= =?us-ascii?Q?N8ZiLPoqcHmBauiRCyaoiKc4JnLR/Rs4FZbwl6iUGyz2gEU69XF3rrtXjfBt?= =?us-ascii?Q?zlmkfKutfxdYmOo99b7dbORKT+fGY4uYo+zTjMZqOLJv8pR3vzYlLK+Ira9i?= =?us-ascii?Q?goAaYJtBmPOp/yNwoXgiE+B7VR24VEtK9NvYGcs3I5m1MT4/GqDLTZ6ryPkL?= =?us-ascii?Q?7FxTbwunhULOr23Ws/VTQLkyVFqb4aiJPWsCd6cwdQaJNvEzmMvrZRmYvlkb?= =?us-ascii?Q?vPrxe/KaCVG40E5Ac6ID0lsVtdHNK0CBmNgp+BalQ/qaszYz2eSDJhetvs2J?= =?us-ascii?Q?QNcbl/kPVhL5VuFxddIn4VtJpthtmS/RoDnRMOBimufhXC/OE9TwrFKQUzer?= =?us-ascii?Q?in2+LUZgXyJluWiR78AYOhL1ZIziaLrQUUsbiPFZCNUGCUET2C/+YYzj1wue?= =?us-ascii?Q?c0Krwr/DEpgynzmiI6WRFFP8UHz6WuzUz5djU9MP53kpLeAh2eFmzsajrncD?= =?us-ascii?Q?u+rPfm8XT28Fr7NEMSrT1fBGVDhDQdTGxj4T4R4Bs9mq+WjCCkb878u94ZhW?= =?us-ascii?Q?9iC78D2DikOpfiCpp9kYN1jE0YWOVrY0YtqDYDDKPXp/ijhPASCRtsCbRkF7?= =?us-ascii?Q?7d6taeKJQaNF+NQlV38F8aOvmzIorIckCuueX9aKQYNuxTRVIbb8mTL2ghLK?= =?us-ascii?Q?nnUf0hpbEjaz2bGghXj2FCiQ0qe080yQwttadkkiHuB6Q7AOISzu6dBA/L5d?= =?us-ascii?Q?L8CJPP5xYjyvR3gHrTZ70jCktIuVUrtndFC2CrLVVGTcCJxg7mhxho70m50j?= =?us-ascii?Q?2z8z5xHN3eC/ixWd5p73LF258iW2Ny6oJi/S3FqDCAXe6EV19l4pY2UdMMJO?= =?us-ascii?Q?11/RWetlwbTAZKxw0ZsuTO7VtoL5Cdl2l8NYok3vYPyver5K7pNMqPciqmnl?= =?us-ascii?Q?lismqWIlL5HruhViq7YLwzl4jnDFFhvjxTLF5XfrasGKAKhwGRPe0jyijQSJ?= =?us-ascii?Q?U2H3kLuFs+eiWDKTi7lsv89XxluQpoiK93XZnNzagK4XqJzcK5fYYrxxc4jb?= =?us-ascii?Q?LdsXcaTy?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-Network-Message-Id: 68882ca1-6069-4ed2-4b6a-08d8c37abb20 X-MS-Exchange-CrossTenant-AuthSource: VI1PR0401MB2382.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Jan 2021 10:51:56.8826 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: dFGKZTTs87MRFGMiME0aqdmCDPrSTWX6u4av5jmjZQzMTGTv3PRXtQJMdF49K1n4 X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR04MB7279 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2021/1/28 =E4=B8=8B=E5=8D=886:34, David Sterba wrote: > On Thu, Jan 28, 2021 at 08:30:21AM +0800, Qu Wenruo wrote: >>>> =C2=A0=C2=A0 btrfs: support subpage for extent buffer page release >>> >>> I don't have this patch in my inbox so I can't reply to it directly, bu= t >>> you include refcount.h, but then use normal atomics.=C2=A0 Please used = the >>> actual refcount_t, as it gets us all the debugging stuff that makes >>> finding problems much easier.=C2=A0 Thanks, >> >> My bad, my initial plan is to use refcount, but the use case has valid 0 >> refcount usage, thus refcount is not good here. >=20 > In case you need to shift the "0" you can use refcount_dec_not_one or > refcount_inc/dec_not_zero, but I haven't seen the code so don't know if > this applies in your case. >=20 In the code, what we want is inc on zero, which will cause warning on=20 refcount. (initial subpage allocation has zero ref, then increased to=20 one when one eb is attached to the page) But maybe I can change the timing so that we can use refcount. Current code uses ASSERT()s to prevent underflow, so it would be=20 sufficient for current code base though. I'll investigate more time on this topic in next update. Thanks, Qu