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

Al Viro
2018-10-13T08:05:11Z

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()...