2016-12-06 0:19 GMT+01:00 Andreas Grünbacher <andreas.gruenbacher@xxxxxxxxx>: > 2016-12-05 23:58 GMT+01:00 Patrick Plagwitz <Patrick_Plagwitz@xxxxxx>: >> On 12/05/2016 08:37 PM, Andreas Grünbacher wrote: >>> 2016-12-05 17:25 GMT+01:00 J. Bruce Fields <bfields@xxxxxxxxxxxx>: >>>> On Mon, Dec 05, 2016 at 04:36:03PM +0100, Miklos Szeredi wrote: >>>>> On Mon, Dec 5, 2016 at 4:19 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: >>>>>>> Can NFS people comment on this? Where does the nfs4_acl come from? >>>>>> >>>>>> This is the interface the NFS client provides for applications to modify >>>>>> NFSv4 ACLs on servers that support them. >>>>> >>>>> Fine, but why are we seeing this xattr on exports where no xattrs are >>>>> set on the exported fs? >>>> >>>> I don't know. I took another look at the original patch and don't see >>>> any details on the server setup: which server is it (knfsd, ganesha, >>>> netapp, ...)? How is it configured? >>>> >>>>>>> What can overlayfs do if it's a non-empty ACL? >>>>>> >>>>>> As little as possible. You can't copy it up, can you? So any attempt >>>>>> to support it is going to be incomplete. >>>>> >>>>> Right. >>>>> >>>>>> >>>>>>> Does knfsd translate posix ACL into NFS acl? If so, we can translate >>>>>>> back. Should we do a generic POSIX<->NFS acl translator? >>>>>> >>>>>> knsd does translate between POSIX and NFSv4 ACLs. It's a complicated >>>>> >>>>> This does explain the nfs4_acl xattr on the client. Question: if it's >>>>> empty, why have it at all? >>>> >>>> I'm honestly not sure what's going on there. I'd be curious to see a >>>> network trace if possible. >>> >>> I do see "system.nfs4_acl" attributes on knfsd exported filesystems >>> that support POSIX ACLs (for ext4: "mount -o acl"). For exported >>> filesystem that don't support POSIX ACLs (ext4: mount -o noacl), that >>> attribute is missing. The attribute shouldn't be empty though; when >>> the file has no real ACL, "system.nfs4_acl" represents the file mode >>> permissions. The "system.nfs4_acl" attribute exposes the information >>> on the wire; there is no resonable way to translate that into an ACL >>> on another filesystem, really. >>> >>> Patrick, what does 'getfattr -m- -d /nfs/file' give you? >>> >> getfattr -m - -d nfs/folder -e text gives >> >> # file: nfs/folder/ >> system.nfs4_acl="\000\000\000^C\000\000\000\000\000\000\000\000\000^V^A<E7>\000\000\000^FOWNER@\000\000\000\000\000\000\000\000\000\000\000^R\000<A1>\000\000\000^FGROUP@\000\000\000\000\000\000\000\000\000\000\000^R\000<A1>\000\000\000 >> EVERYONE@\000\000" >> >> Those are 80 bytes. I checked again and vfs_getxattr indeed returns size=80. >> It just looked empty because the first byte is 0... Ok, so nfs4_acl is not >> empty after all and checking *value == 0 does not tell if there are actually >> ACLs present or not, sorry for the confusion. >> >> You are right, when I mount the exported fs with noacl the problem goes away. >> You already helped me there, thanks. >> >> Still, I think there should be a way to copy up files that actually have no >> ACLs since acl is often the default for ext4 mounts and giving an "Operation >> not supported" for random open(2)s is not a very good way to convey what's >> going on. > > It's not hard to come up with a heuristic that determines if a > system.nfs4_acl value is equivalent to a file mode, and to ignore the > attribute in that case. (The file mode is transmitted in its own > attribute already, so actually converting .) That way, overlayfs could > still fail copying up files that have an actual ACL. It's still an > ugly hack ... Actually, that kind of heuristic would make sense in the NFS client which could then hide the "system.nfs4_acl" attribute. Andreas -- 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
