On Thu, Oct 20, 2011 at 04:32:04PM +0530, Aneesh Kumar K.V wrote: > On Thu, 20 Oct 2011 05:19:46 -0400, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > On Thu, Oct 20, 2011 at 05:14:34AM -0400, J. Bruce Fields wrote: > > > > > Does it really make sense to use a string here just to pick between the > > > > > three choices OWNER@, GROUP@, and EVERYONE@? Why not just another small > > > > > integer? Is the goal to expand this somehow eventually? > > > > > > > > > > I guess Andreas wanted the disk layout to be able to store user@domain > > > > format if needed. > > > > > > Is that likely? For that to be useful, tasks would need to be able to > > > run as user@domain strings. And we'd probably want owners and groups to > > > also be user@domain strings. > > > > > > The container people seem to eventually want to add some kind of > > > namespace identifier everywhere: > > > > > > http://marc.info/?l=linux-kernel&m=131836778427871&w=2 > > > > > > in which case I guess we'd likely end up with (uid, user namespace id) > > > instead of user@domain? > > > > > > Storing strings is an extremly stupid idea. The only thing that would > > make sense would be storing a windows-style 128-bit GUID. > > > > How about updating the richacl_xattr as below > > struct richace_xattr { > __le16 e_type; > __le16 e_flags; > __le32 e_mask; > __le32 e_size; > u8 e_id[0]; > }; > > now e_flags can contain ACE4_SPECIAL_WHO to indicate value in e_id > indicate special who values (which could be 1 byte value indicating > OWNER@, GROUP@ or EVERYONE@), ACE4_UNIXID_WHO, to indicate value > in e_id is the little endian value of unix id. ACE_WINSID_WHO to > indicate e_id is the 128 bit array containing SID value. ? That's effectively still a string. Would it be so bad to have to introduce another xattr type if we needed a new id type? You'll have to modify the filesystem and the userspace tools and everything anyway, won't you? But if we decide we don't need strings, then at a minimum let's make these some fixed small size. You could do something like: struct richace_xattr { __le16 e_type; __le16 e_flags; __le32 e_mask; __le32 e_id[4]; } and just use e_id[0] for now. That would still leave room for a 128-bit id, or for a 32-bit uid + some-size namespace-id. Cc'ing Eric Biederman in hopes of finding out whether that would satifsy whatever wacky future ideas might be expected for user namespaces. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
