On Fri, 2019-02-15 at 13:14 +0800, Yihao Wu wrote: > On 2019/2/13 7:50 PM, Jeff Layton wrote: > > On Wed, 2019-02-13 at 16:41 +0800, Yihao Wu wrote: > > > Hi all, > > > > > > When looking into "Failures: generic/467" given by xfstests, I > > > found that NFSv3 > > > didn't implement LOOKUPP. I know that this might be by design. > > > But LOOKUPP was > > > meant to replace ".." in NFSv3, right? > > > > > > xfstests's generic/467 test case performs the following sequence > > > of operations. > > > > > > name_to_handle -> drop_caches -> open_by_handle > > > > > > Dentry becomes disconnected due to drop_caches. NFSv3 doesn't > > > support LOOKUPP. > > > So when it performs open_by_handle to an directory, this test > > > case fails. > > > > > > I did some small experiment by implementing LOOKUPP for NFSv3. > > > The way I tried > > > is to merely pass ".." to nfs3_proc_lookup. And it seems to work. > > > At least it's > > > a workaround for xfstests. > > > > > > I'm curious whether this sort of simulation of LOOKUPP will work > > > or make sense. > > > > > > Thanks, > > > Yihao Wu > > > > v3 was mostly designed with unix-like clients in mind. For v4, the > > spec > > writers cast a wider net and decided not to put special meaning on > > lookups of "." and "..", but they still needed a way to do a lookup > > of > > "..". > > > > The question is why you want to implement LOOKUPP in v3. Mostly we > > added > > it to the client to support reexporting NFSv4 filesystems via > > NFSv3. Are > > you looking to reexport v3 filesystems for some reason? > > > > Thanks a lot for your reply, Jeff! > > I'm just managing to figure out the source of this xfstests failure, > that > open_by_handle is simply not working for NFSv3 after drop_caches. I > think NFSv3 > might become able to reconnect_path too, with LOOKUP "..". However > it's not, > because nfs_get_parent fails as long as LOOKUPP is not supported. > > My server & client both support NFSv3. Can I take it that re- > exporting is not a > required option in this case? While linux client don't generally need it, you may want to note that some non-linux clients do need to make use of LOOKUP ".." in order to navigate the server's namespace. I know that the Solaris client does rely on it, and I suspect that FreeBSD does too. I'd therefore strongly recommend that you do support the LOOKUP ".." functionality in your server if you care about NFSv3 client interoperability. Cheers Trond -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@xxxxxxxxxxxxxxx
