On Tue, Mar 17, 2015 at 10:31:51AM +0100, David Sterba wrote:
> On Mon, Mar 16, 2015 at 05:36:05PM +0000, Al Viro wrote:
> > On Mon, Mar 16, 2015 at 04:33:49AM -0700, Omar Sandoval wrote:
> > > Get either READ or WRITE out of iter->type.
> >
> > Umm...
> >
> > > + * Get one of READ or WRITE out of iter->type without any other flags OR'd in
> > > + * with it.
> > > + */
> > > +static inline int iov_iter_rw(const struct iov_iter *i)
> > > +{
> > > + return i->type & RW_MASK;
> > > +}
> >
> > TBH, I would turn that into a macro. Reason: indirect includes.
>
> Agreed, but the proposed define is rather cryptic and I was not able to
> understand the meaning on the first glance.
>
> > #define iov_iter_rw(i) ((0 ? (struct iov_iter *)0 : (i))->type & RW_MASK)
>
> This worked for me, does not compile with anything else than
> 'struct iov_iter*' as i:
>
> #define iov_iter_rw(i) ({ \
> struct iov_iter __iter = *(i); \
> (i)->type & RW_MASK; \
> })
>
> The assignment is optimized out.
[-cc individual fs maintainers to avoid all of these email bounces,
should've looked a bit closer at that get_maintainer.pl output...]
I agree that this is a bit more readable, but it evaluates i twice.
That's an easy fix, just do __iter.type instead of (i)->type, but
there's still the possibility of someone passing in something called
__iter as i, and the fix for that tends to be "add more underscores". At
the very least, Al's macro could probably use a comment explaining
what's going on there, though.
--
Omar
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