Following are bit flags which kernel / VFS / fsdriver would have to handle specially, to provide enforcement or correct behavior of them: - FILE_ATTRIBUTE_READONLY - enforce that data modification or unlink is disallowed when set - FILE_ATTRIBUTE_COMPRESSED - enforce compression on filesystem when set - FILE_ATTRIBUTE_ENCRYPTED - enforce encryption on filesystem when set Then there are HSM flags which for local filesystem would need some cooperation with userspace synchronization software. For network filesystems (SMB / NFS4) they need nothing special, just properly propagating them over network: - FILE_ATTRIBUTE_OFFLINE - FILE_ATTRIBUTE_PINNED - FILE_ATTRIBUTE_UNPINNED About following 2 flags, I'm not sure if the kernel / VFS / fs driver has to do something or it can just store bits to fs: - FILE_ATTRIBUTE_TEMPORARY - FILE_ATTRIBUTE_NO_SCRUB_DATA ======================================================================= And there is still unresolved issue with FILE_ATTRIBUTE_READONLY. Its meaning is similar to existing Linux FS_IMMUTABLE_FL, just FILE_ATTRIBUTE_READONLY does not require root / CAP_LINUX_IMMUTABLE. I think that for proper support, to enforce FILE_ATTRIBUTE_READONLY functionality, it is needed to introduce new flag e.g. FS_IMMUTABLE_FL_USER to allow setting / clearing it also for normal users without CAP_LINUX_IMMUTABLE. Otherwise it would be unsuitable for any SMB client, SMB server or any application which would like to use it, for example wine. Just to note that FreeBSD has two immutable flags SF_IMMUTABLE and UF_IMMUTABLE, one settable only by superuser and second for owner. Any opinion?
