[topic proposal] dealing with ->d_revalidate() right ways (automounting, atomic opens and the whole mess around that)

[Al Viro <viro@ZenIV.linux.org.uk>]

	That's going to be the next big change of VFS architecture; bits
and pieces had been discussed on lists and in private mail, but it would
be really useful to sit down and discuss that face to face with everyone
involved.

	* ->follow_link() is abused for triggering submounts.
	* ->d_revalidate() is abused in many, _many_ ways, including
autofs, NFS "reval_dot" stuff, atomic opens, etc.  Moreover, it has nasty
interplay with crossing mountpoints.
	* NFS handling of atomic opens is near the point where we can
switch to methods that would get proper arguments directly, rather
than abusing ->lookup/->d_revalidate/whatnot.  Again, ->d_revalidate
and mountpoint crossing are stumbling blocks.  And NFS4 bits around
open are just plain scary...
	* NFSv4 has rather unpleasant stuff in submount handling - what
it does with ->mnt_devname doesn't bear describing in polite company and
it actually doesn't work right with mount --bind (moderately) and
mountinfo contents (completely).  Both issues are fixable and that gets
entangled into the aforementioned ball of barbed wire...

	Who might want to be there: nfsd/nfs/cifs/afs/autofs4 and general
VFS-interested folks.