Re: mm/filemap.c:4249:1: sparse: sparse: Using plain integer as NULL pointer

[Nhat Pham]

On Tue, Nov 7, 2023 at 8:30 AM kernel test robot <lkp@xxxxxxxxx> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   be3ca57cfb777ad820c6659d52e60bbdd36bf5ff
> commit: cf264e1329fb0307e044f7675849f9f38b44c11a cachestat: implement cachestat syscall
> date:   5 months ago
> config: s390-randconfig-r123-20231107 (https://download.01.org/0day-ci/archive/20231108/202311080014.GABRIG2T-lkp@xxxxxxxxx/config)
> compiler: s390-linux-gcc (GCC) 13.2.0
> reproduce: (https://download.01.org/0day-ci/archive/20231108/202311080014.GABRIG2T-lkp@xxxxxxxxx/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202311080014.GABRIG2T-lkp@xxxxxxxxx/
>
> 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:4249:1: sparse: sparse: Using plain integer as NULL pointer
> >> mm/filemap.c:4249:1: sparse: sparse: Using plain integer as NULL pointer
> >> mm/filemap.c:4249:1: sparse: sparse: Using plain integer as NULL pointer
> >> mm/filemap.c:4249:1: sparse: sparse: Using plain integer as NULL pointer
>
> vim +4249 mm/filemap.c
>
>   4214
>   4215  /*
>   4216   * The cachestat(2) system call.
>   4217   *
>   4218   * cachestat() returns the page cache statistics of a file in the
>   4219   * bytes range specified by `off` and `len`: number of cached pages,
>   4220   * number of dirty pages, number of pages marked for writeback,
>   4221   * number of evicted pages, and number of recently evicted pages.
>   4222   *
>   4223   * An evicted page is a page that is previously in the page cache
>   4224   * but has been evicted since. A page is recently evicted if its last
>   4225   * eviction was recent enough that its reentry to the cache would
>   4226   * indicate that it is actively being used by the system, and that
>   4227   * there is memory pressure on the system.
>   4228   *
>   4229   * `off` and `len` must be non-negative integers. If `len` > 0,
>   4230   * the queried range is [`off`, `off` + `len`]. If `len` == 0,
>   4231   * we will query in the range from `off` to the end of the file.
>   4232   *
>   4233   * The `flags` argument is unused for now, but is included for future
>   4234   * extensibility. User should pass 0 (i.e no flag specified).
>   4235   *
>   4236   * Currently, hugetlbfs is not supported.
>   4237   *
>   4238   * Because the status of a page can change after cachestat() checks it
>   4239   * but before it returns to the application, the returned values may
>   4240   * contain stale information.
>   4241   *
>   4242   * return values:
>   4243   *  zero        - success
>   4244   *  -EFAULT     - cstat or cstat_range points to an illegal address
>   4245   *  -EINVAL     - invalid flags
>   4246   *  -EBADF      - invalid file descriptor
>   4247   *  -EOPNOTSUPP - file descriptor is of a hugetlbfs file
>   4248   */
> > 4249  SYSCALL_DEFINE4(cachestat, unsigned int, fd,
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

This is a known false positive with s390. See this thread:
https://lore.kernel.org/linux-mm/202305070840.X0G3ofjl-lkp@xxxxxxxxx/