Re: [PATCH] Fix kunmap() argument in sg_miter_stop

Jens Axboe
2008-11-17T09:47:47Z

On Mon, Nov 17 2008, Ingo Molnar wrote:
>
> * Jens Axboe <jens.axboe@oracle.com> wrote:
>
> > On Mon, Nov 17 2008, Jens Axboe wrote:
> > > On Mon, Nov 17 2008, Ingo Molnar wrote:
> > > >
> > > > * Jens Axboe <jens.axboe@oracle.com> wrote:
> > > >
> > > > > On Mon, Nov 17 2008, Ingo Molnar wrote:
> > > > > >
> > > > > > * Jens Axboe <jens.axboe@oracle.com> wrote:
> > > > > >
> > > > > > > +#define kunmap(p) \
> > > > > > > + do { \
> > > > > > > + struct page *__p; \
> > > > > > > + (void) (&__p == &(p)); \
> > > > > > > + __kunmap(p); \
> > > > > > > + } while (0)
> > > > > > > +
> > > > > > > +#define kunmap_atomic(a, t) \
> > > > > > > + do { \
> > > > > > > + void *__p; \
> > > > > > > + (void) (&__p == &(a)); \
> > > > > > > + __kunmap_atomic(a, t); \
> > > > > > > + } while (0)
> > > > > >
> > > > > > Agreed - but please use the typecheck() primitive. (linux/typecheck.h)
> > > > >
> > > > > Neat, didn't know about that, thanks.
> > > >
> > > > and ack on your patch obviously. Feel free to push it via the block
> > > > tree straight away, it doesnt collide with anything pending in the x86
> > > > tree.
> > > >
> > > > Acked-by: Ingo Molnar <mingo@elte.hu>
> > >
> > > The kunmap() bit is easy to do as I mentioned, but the kunmap_atomic()
> > > gets a bit more ugly. Lots of users can just be switched to void *
> > > types, but some get ugly like:
> > >
> > > static struct page **shmem_dir_map(struct page *page)
> > > return (struct page **)kmap_atomic(page, KM_USER0);
> > > }
> > >
> > > -static inline void shmem_dir_unmap(struct page **dir)
> > > +static inline void shmem_dir_unmap(void *dir)
> > > {
> > > kunmap_atomic(dir, KM_USER0);
> > > }
> > >
> > > and others again like fs/exec.c:remove_arg_zero() would really like to
> > > use a char * type since it dereferences it.
> > >
> > > I think the kunmap_atomic() change it the most needed part of the patch,
> > > but I don't think it can come for free (eg, we have to add variable to
> > > the above function).
> >
> > OK, (void *) cast works fine when I fixed it. Here's a normal build diff
> > to show approximately how bad it is. I expected it to be worse, so it
> > looks quite doable I think.
>
> hm:
>
> 32 files changed, 89 insertions(+), 62 deletions(-)
>
> regarding churn it looks a bit like on the high side. OTOH it's
> trivial, most of the churn is spread-out in various architectures, and
> it can catch real bugs so i'm still acking it.
>
> Could you please send the patch with a full changelog? I've Cc:-ed
> Linus and Andrew - please let us know if you think that this too much
> churn for -rc6.

I'll send out a new version when I've done a full build, to avoid
introducing new warnings. And I'll do that as a proper patch with SOB
and description, etc.

--
Jens Axboe