On Thu, Dec 21, 2017 at 02:00:16PM -0800, Josh Triplett wrote:
> On Thu, Dec 21, 2017 at 02:48:10PM -0700, Ross Zwisler wrote:
> > On Tue, Dec 19, 2017 at 08:58:23AM -0800, Matthew Wilcox wrote:
> > > From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> > >
> > > The __cond_lock macro expects the function to return 'true' if the lock
> > > was acquired and 'false' if it wasn't. We have another common calling
> > > convention in the kernel, which is returning 0 on success and an errno
> > > on failure. It's hard to use the existing __cond_lock macro for those
> > > kinds of functions, so introduce __cond_lock_err() and convert the
> > > two existing users.
> >
> > This is much cleaner! One quick issue below.
> >
> > > Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> > > ---
> > > include/linux/compiler_types.h | 2 ++
> > > include/linux/mm.h | 9 ++-------
> > > mm/memory.c | 9 ++-------
> > > 3 files changed, 6 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> > > index 6b79a9bba9a7..ff3c41c78efa 100644
> > > --- a/include/linux/compiler_types.h
> > > +++ b/include/linux/compiler_types.h
> > > @@ -16,6 +16,7 @@
> > > # define __acquire(x) __context__(x,1)
> > > # define __release(x) __context__(x,-1)
> > > # define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
> > > +# define __cond_lock_err(x,c) ((c) ? 1 : ({ __acquire(x); 0; }))
> > ^
> > I think we actually want this to return c here ^
>
> Then you want to use ((c) ?: ...), to avoid evaluating c twice.
Oh, yep, great catch.
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