On Tue, 11 Nov 2014 16:13:21 +0900 sf...@users.sourceforge.net wrote: > Here is a draft of a new file > Documentation/filesystems/aufs/design/06xattr.txt. > I want you (or anyone) to take a look and send comments back, > particulary about > - new branch attrib. > - the behaviour of getxattr(2) and listxattr(2).
Hello Junjiro, if I understand correctly, aufs cannot know if these "security", "trusted" or "user" attributes are supported by the branches, so the user has to specify them. I think this is a good solution. I don't understand yet why you would collect XATTRs from lower branches, too. In directories, it's clear, because it's not logical if you can see only part of the contents (from the branches which allow access to the directory). The only thing I can imagine is something like - lower branch (ro) has cap_net_admin,cap_net_raw+ep (like ping in SL7) - upper branch (rw) doesn't support xattrs - for some reason, ping is copied up to upper branch then ping would only work for users (except root) if all branches are checked. I wouldn't think this is very important to implement, since the upper branch can easily be chosen so that xattrs work on it, too. I think aufs is mainly used for - allowing "writes" to r/o media (Knoppix, embedded systems, systems which often suffer power loss - then a ramdisk can be used) - a kind of copy-on-write, saving time and disk space (docker) - probably least common: being able to roll back changes very fast (that's what I use it for :-) all of those cases allow using an fs with xattrs as r/w branch. But perhaps there are more reasons to scan all branches for xattrs? Regards, Torsten
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