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

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

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   83e5775d7afda68f6d7576d21f7a080fbfeecc4f
commit: d39c65bc7fcb1dad22dc1585fc669b5bfe5d3108 [14680/14811] cachestat: implement cachestat syscall
config: s390-randconfig-s041-20230507 (https://download.01.org/0day-ci/archive/20230507/202305070840.X0G3ofjl-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=d39c65bc7fcb1dad22dc1585fc669b5bfe5d3108
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout d39c65bc7fcb1dad22dc1585fc669b5bfe5d3108
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=s390 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202305070840.X0G3ofjl-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: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
>> mm/filemap.c:4250:1: sparse: sparse: Using plain integer as NULL pointer

vim +4250 mm/filemap.c

  4215	
  4216	/*
  4217	 * The cachestat(2) system call.
  4218	 *
  4219	 * cachestat() returns the page cache statistics of a file in the
  4220	 * bytes range specified by `off` and `len`: number of cached pages,
  4221	 * number of dirty pages, number of pages marked for writeback,
  4222	 * number of evicted pages, and number of recently evicted pages.
  4223	 *
  4224	 * An evicted page is a page that is previously in the page cache
  4225	 * but has been evicted since. A page is recently evicted if its last
  4226	 * eviction was recent enough that its reentry to the cache would
  4227	 * indicate that it is actively being used by the system, and that
  4228	 * there is memory pressure on the system.
  4229	 *
  4230	 * `off` and `len` must be non-negative integers. If `len` > 0,
  4231	 * the queried range is [`off`, `off` + `len`]. If `len` == 0,
  4232	 * we will query in the range from `off` to the end of the file.
  4233	 *
  4234	 * The `flags` argument is unused for now, but is included for future
  4235	 * extensibility. User should pass 0 (i.e no flag specified).
  4236	 *
  4237	 * Currently, hugetlbfs is not supported.
  4238	 *
  4239	 * Because the status of a page can change after cachestat() checks it
  4240	 * but before it returns to the application, the returned values may
  4241	 * contain stale information.
  4242	 *
  4243	 * return values:
  4244	 *  zero        - success
  4245	 *  -EFAULT     - cstat or cstat_range points to an illegal address
  4246	 *  -EINVAL     - invalid flags
  4247	 *  -EBADF      - invalid file descriptor
  4248	 *  -EOPNOTSUPP - file descriptor is of a hugetlbfs file
  4249	 */
> 4250	SYSCALL_DEFINE4(cachestat, unsigned int, fd,

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