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Wed, 8 Sep 2021 07:27:24 +0000 To: linux-fsdevel From: Allison Henderson Subject: [TOPIC LPC] Filesystem Shrink Message-ID: <3bffa6b2-981f-9a64-9fed-f211bfe501cd@oracle.com> Date: Wed, 8 Sep 2021 00:27:23 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY5PR17CA0020.namprd17.prod.outlook.com (2603:10b6:a03:1b8::33) To BY5PR10MB4306.namprd10.prod.outlook.com (2603:10b6:a03:211::7) MIME-Version: 1.0 Received: from [192.168.1.167] (67.1.243.157) by BY5PR17CA0020.namprd17.prod.outlook.com (2603:10b6:a03:1b8::33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4500.14 via Frontend Transport; Wed, 8 Sep 2021 07:27:24 +0000 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: c643b366-5f57-497e-6ce9-08d9729a1a9c X-MS-TrafficTypeDiagnostic: SJ0PR10MB4447: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; 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It sounds like the talk is of interest, but folks recommended I forward the discussion to fsdevel for more feed back. Below is the abstract for the talk: File system shrink allows a file system to be reduced in size by some specified size blocks as long as the file system has enough unallocated space to do so. This operation is currently unsupported in xfs. Though a file system can be backed up and recreated in smaller sizes, this is not functionally the same as an in place resize. Implementing this feature is costly in terms of developer time and resources, so it is important to consider the motivations to implement this feature. This talk would aim to discuss any user stories for this feature. What are the possible cases for a user needing to shrink the file system after creation, and by how much? Can these requirements be satisfied with a simpler mkfs option to backup an existing file system into a new but smaller filesystem? In the cases of creating a rootfs, will a protofile suffice? If the shrink feature is needed, we should further discuss the APIs that users would need. Beyond the user stories, it is also worth discussing implementation challenges. Reflink and parent pointers can assist in facilitating shrink operations, but is it reasonable to make them requirements for shrink? Gathering feedback and addressing these challenges will help guide future development efforts for this feature. Comments and feedback are appreciated! Thanks! Allison