Re: RFC: renameat(): Add a RENAME_REMOVE flag to unlink hardlinks

[Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>]

On Fri, Nov 21, 2014 at 10:20:54PM +0000, Pádraig Brady wrote:

> >> That said, would you still like me to take a stab at a proposal to the
> >> POSIX folks that would relax the requirements to allow
> >> implementation-defined behavior when the two arguments to rename
> >> describe the same file but via different directory entries?
> 
> I guess there is no point discussing in POSIX and adding extra
> implementation options if no implementations do/will act accordingly.
> 
> Linux can decide to do that independently, if appropriate.
> This is one of those borderline cases where we balance
> accretion of cruft vs incompatibility.
> On consideration, I'm OK with keeping the existing
> rename() behavior for compat and adding the new flag.
> That said I still can't think of anything depending
> rename() doing nothing with hardlinked source and dest.

You do realize that it opens a very nasty can of worms for filesystems that
are e.g. case-insensitive to some extent?  How do you tell links from
alternative equivalent spellings of the name?