Re: [PATCH 27/32] xfs: Add parent pointer ioctls

Darrick J. Wong
2024-04-16T19:07:34Z

On Tue, Apr 16, 2024 at 12:01:52PM -0700, Christoph Hellwig wrote:
> On Tue, Apr 16, 2024 at 11:52:09AM -0700, Darrick J. Wong wrote:
> > > > <nod> But does exportfs actually want parent info for a nondirectory?
> > > > There aren't any stubs or XXX/FIXME comments, and I've never heard any
> > > > calls (at least on fsdevel) for that functionality.
> > >
> > > It doesn't. It would avoid having disconnected dentries, but
> > > disconnected non-directory dentries aren't really a problem.
> >
> > For directories, I think the dotdot lookup is much cheaper than scanning
> > the attrs to find the first nongarbage XFS_ATTR_PARENT entry.
>
> It is.
>
> But I was confused again, it's been a while since I worked on that code..
>
> We do the full reconnection for non-directories if NFSD asks for it (the
> XFS or VFS handle code won't hit this because our acceptable callback
> always returns true). That code does a readdir on the parent and
> returns the name when it finds the inode number. For files without
> crazy number of hardlinks just looking over the parent pointers would
> be a lot more efficient for that.

Ohhhh, does that happens outside of XFS then? No wonder I couldn't find
what you were talking about. Ok I'll go look some more.

--D