Re: [PATCH] VFS: Sanity check mount flags passed to change_mnt_propagation()

[Matthew Wilcox <matthew@wil.cx>]

On Fri, Aug 27, 2010 at 01:51:06PM -0400, Bob Copeland wrote:
> On Fri, Aug 27, 2010 at 1:43 PM, Valerie Aurora <vaurora@redhat.com> wrote:
> > On Thu, Aug 26, 2010 at 07:14:36PM -0600, Matthew Wilcox wrote:
> >> Hrm. ?I think we can do this a bit more pithily.
> >>
> >> ? ? ? /* Only one propagation flag should be set, and no others */
> >> ? ? ? if (hweight32(type) != 1 &&
> >> ? ? ? ? ? (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
> >> ? ? ? ? ? ? ? return 0;
> >>
> >> Too clever?
> >
> > I was hoping someone would go find the best bitop for me, thanks. :)
> > hweight32() is an awkward name but the comment makes it clear. ?I'm
> > happy with either.
> >
> > Thanks for the help,
> 
> Didn't read surrounding code, but is that supposed to be '||'?
> 
> Otherwise the case where only a single non-propagation flag is
> set no longer returns 0...

Val's original code returned 0 as failure.  So a single non-propagation
flag set shouldn't return 0.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."