Re: [PATCH v3 1/3] namei: implement O_BENEATH-style AT_* flags

On Sat, Oct 13, 2018 at 08:33:19AM +0100, Al Viro wrote:

Pardon me, but... huh?  The reason for your two calls of dirfd_path_init() is,
AFAICS, the combination of absolute pathname with both LOOKUP_XDEV and
LOOKUP_BENEATH at the same time.  That combination is treated as if the pathname
had been relative.  Note that LOOKUP_BENEATH alone is ignored for absolute ones
(and with a good reason - it's a no-op on path_init() level in that case).

What the hell?  It complicates your code and doesn't seem to provide any benefits
whatsoever -- you could bloody well have passed the relative pathname to start with.

IDGI...  Without that kludge it becomes simply "do as we currently do for absolute
pathnames, call dirfd_path_init() for relative ones".  And I would argue that
taking LOOKUP_BENEATH handling out of dirfd_path_init() into path_init() (relative)
case would be a good idea.

As it is, the logics is very hard to follow.

	... and it fails on LOOKUP_BENEATH anyway.  Egads...  So that's for your
LOOKUP_CHROOT ;-/  IMO that's awful, especially with the way you've spread those
LOOKUP_CHROOT cases between these two.

	Why not simply have O_THISROOT pick root by dirfd and call file_open_root()?
And if something wants it for stat(), etc. just have them use it combined with
O_PATH and pass the result to ...at()...