Re: [linux-next:master 14680/14811] mm/filemap.c:4250:1: sparse: sparse: Using plain integer as NULL pointer

[Heiko Carstens <hca@linux.ibm.com>]

On Mon, May 08, 2023 at 09:45:56AM -0700, Nhat Pham wrote:
> On Sat, May 6, 2023 at 5:28 PM kernel test robot <lkp@intel.com> wrote:
> > sparse warnings: (new ones prefixed by >>)
> >    mm/filemap.c:1416:17: sparse: sparse: context imbalance in 'migration_entry_wait_on_locked' - unexpected unlock
> > >> mm/filemap.c:4250:1: sparse: sparse: Using plain integer as NULL pointer
> > >> mm/filemap.c:4250:1: sparse: sparse: Using plain integer as NULL pointer
> > >> mm/filemap.c:4250:1: sparse: sparse: Using plain integer as NULL pointer
...
> > > 4250  SYSCALL_DEFINE4(cachestat, unsigned int, fd,
> 
> Hmm I couldn't see where I used 0 as the null pointer. Maybe
> this is a false positive or a result of not wiring up the syscall
> for s390? Especially since this is pointed toward the macro
> line (SYSCALL_DEFINE).
> 
> cc-ing this to s390 maintainers and the s390 mailing list...
> Could you help me debug this? Thanks!

Just ignore, this is a known false positive with s390's SYSCALL_DEFINE()
implementation vs sparse. I looked into it once, but couldn't figure out
how to silence sparse.
IIRC, the __TYPE_IS_PTR() macro causes this.