Re: [PATCH -V14 05/11] vfs: Support null pathname in readlink

[Nick Piggin <npiggin@suse.de>]

On Wed, Jul 07, 2010 at 10:02:12PM +0530, Aneesh Kumar K. V wrote:
> On Thu, 8 Jul 2010 01:27:06 +1000, Nick Piggin <npiggin@suse.de> wrote:
> > This (and all the others) is really ugly overloading of syscall
> > arguments IMO, and the changelog is seriously lacking for such
> > changes.
> 
> Initially we had  freadlink
> 
> http://lkml.org/lkml/2010/5/12/222
> 
> We updated the patches to use the existing readlinkat interface because
> utimensat(2) already exposed a similar interface. So it should be ok to
> expect that other *at call behaved in a similar way ?

I'm not sure whether it's OK or not. Probably is, it is a slight API
change though, that should at least be noted in the changelog.


> > This also changes the the syscall API of existing calls; from reading
> > the path at NULL, to switching to a completely different syscall.
> > Perhaps you're assuming nobody relies on SIGSEGV / mmapped NULL address
> > there, but even then you surely need to document the changed semantics
> > somewhere (and document the new syscall semantics properly).
> 
> 
> Yes this would need a documentation update. But i guess since we already
> have utimensat(2) behaving similarly we are ok to extent readlinkat,
> linkat and faccessat on similar lines ?

At least there is precedent. Pretty ugly though :( Well if others
(Christoph and Al, primarily) think it's OK then fine by me. But
please put comments or changelog for API changes such that a man page
writer could easily update it.