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

[kernel test robot <lkp@intel.com>]

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@intel.com/config)
compiler: s390-linux-gcc (GCC) 13.2.0
reproduce: (https://download.01.org/0day-ci/archive/20231108/202311080014.GABRIG2T-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311080014.GABRIG2T-lkp@intel.com/

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,

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