On Sat, 2008-08-02 at 17:33 -0400, J. Bruce Fields wrote: > On Sat, Aug 02, 2008 at 09:42:32PM +0100, David Woodhouse wrote: > > On Sat, 2008-08-02 at 14:26 -0400, J. Bruce Fields wrote: > > > Could you add a readdirplus vfs operation which took a flag indicating > > > how much extra information you're going to need? > > > > Actually, if we're screwing with readdir then xfs would like to know how > > much it's going to be asked to read, rather than just have the filldir > > callback return zero when it's done. > > OK. > > > > The three cases where readdir can be called are: > > > - ordinary readdir, for which the existing filldir_t provides > > > all the information needed. > > > - nfsv3 readdirplus, where the only additional information > > > needed is whether there's a mountpoint. > > > > It also wants a file handle. > > Oops, right. > > > For which I think it just needs > > i_generation in addition to the information it already has. > > Typically, right, though the filesystem's allowed some choice about what > exactly it wants to use in the filehandle. I don't know how the various > filesystems are actually using that in practice. That's OK. If we do ->lookup_fh() and they're making their own, they can put what they like in it. > > > - nfsv4 readdir, where we may need all the stat info, acls, > > > etc., etc. > > > > We _might_, but most of the time we won't. It might be OK to fall back > > to the existing double-buffer hack for the cases where we _do_ need that > > extra information. > > How bad is the "double-buffer hack" anyway? Rather than have this as a > fallback case that's rarely used (hence rarely tested), it might be > simpler just to use it for everything if we're going to use it at all. It's certainly a good enough answer for now, which is why I've posted the patches to do exactly that. And yes, I have wondered the same myself, since realising that we'll need a full lookup for some NFSv4 clients anyway. Or maybe the full ->lookup_locked(), perhaps... -- dwmw2 -- 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
