Re: [HPDD-discuss] [RFC PATCH 1/5] new helper: iov_iter_rw()
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