On Thu, 2008-07-31 at 21:31 -0400, Chuck Lever wrote: > On Thu, Jul 31, 2008 at 9:00 PM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > On Thu, 2008-07-31 at 20:53 -0400, Chuck Lever wrote: > >> For now it is sufficient, IMO. NFSv4 doesn't implement a readdirplus > >> operation, and the performance benefits of NFSv3 readdirplus are > >> equivocal -- there isn't a strong desire to replicate the complexity > >> of NFSv3 readdirplus in NFSv4. I'm not even sure you can do it even > >> with a single compound RPC, so even in the long run NFSv4 may not ever > >> have the locking issues that NFSv3 does here. > > > > AFAICT NFSv4 does have the same recursion issues already. The call trace > > goes fs->readdir() ... nfsd4_encode_dirent() ... > > nfsd4_encode_dirent_fattr() ... lookup_one_len() ... fs->lookup(). > > > > Or am I mistaken? > > It looks like it needs a directory entry's dentry for a couple of reasons: > > 1. To determine whether a directory entry is a mount point > > 2. If the client has asked for file handles (via a bitmask) for the > directory entries Those are needed by NFSv3 too -- and can be handled with a lookup_fh() method in the file system which is guaranteed to be called from within the filldir callback, and some support in the VFS for checking if it's a mountpoint. NFSv4 introduces another problem though, which is that it seems to be able to return the _full_ getattr() results for each object, and there's no real way round the fact that we need to do the ->lookup() for that. If sane clients aren't expected to _ask_ for that, though, then perhaps it would be OK to fall back to something like the existing readdir-to-buffer hack for that case, while most normal clients won't trigger it. -- David Woodhouse Open Source Technology Centre David.Woodhouse@xxxxxxxxx Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
