Hi Jia, On Wed, Aug 31, 2022 at 08:31:20PM +0800, Jia Zhu wrote: > [Kernel Patchset] > =============== > Git tree: > https://github.com/userzj/linux.git zhujia/shared-domain-v1 > Git web: > https://github.com/userzj/linux/tree/zhujia/shared-domain-v1 > > [Background] > ============ > In ondemand read mode, we use individual volume to present an erofs > mountpoint, cookies to present bootstrap and data blobs. > > In which case, since cookies can't be shared between fscache volumes, > even if the data blobs between different mountpoints are exactly same, > they can't be shared. > > [Introduction] > ============== > Here we introduce erofs shared domain to resolve above mentioned case. > Several erofs filesystems can belong to one domain, and data blobs can > be shared among these erofs filesystems of same domain. As we discussed in the previous community meeting, I agree that is useful and it's the prerequisite of storage/page cache sharing between blocks among different images (filesystems). Thanks for your time and effort on this! > > [Usage] > Users could specify 'domain_id' mount option to create or join into a > domain which reuses the same cookies(blobs). > > [Design] > ======== > 1. Use pseudo mnt to manage domain's lifecycle. > 2. Use a linked list to maintain & traverse domains. > 3. Use pseudo sb to create anonymous inode for recording cookie's info > and manage cookies lifecycle. > > [Flow Path] > =========== > 1. User specify a new 'domain_id' in mount option. > 1.1 Traverse domain list, compare domain_id with existing domain.[Miss] > 1.2 Create a new domain(volume), add it to domain list. > 1.3 Traverse pseudo sb's inode list, compare cookie name with > existing cookies.[Miss] > 1.4 Alloc new anonymous inodes and cookies. > > 2. User specify an existing 'domain_id' in mount option and the data > blob is existed in domain. > 2.1 Traverse domain list, compare domain_id with existing domain.[Hit] > 2.2 Reuse the domain and increase its refcnt. > 2.3 Traverse pseudo sb's inode list, compare cookie name with > existing cookies.[Hit] > 2.4 Reuse the cookie and increase its refcnt. > > [Test] > ====== > Git web: (More test cases will be added.) > https://github.com/userzj/demand-read-cachefilesd/tree/shared-domain I'd suggest integrating to erofs-utils testcases directly, see https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git/log/?h=experimental-tests-fscache Thanks, Gao Xiang
