Re: [PATCH] mm/damon/core: remove declaration of kdamond_fn()

Hi Zenghui,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Zenghui-Yu/mm-damon-core-remove-declaration-of-kdamond_fn/20260828-003953
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260827163953.83520-1-zenghui.yu%40linux.dev
patch subject: [PATCH] mm/damon/core: remove declaration of kdamond_fn()
config: xtensa-randconfig-r073-20260828 (https://download.01.org/0day-ci/archive/20260828/[email protected]/config)
compiler: xtensa-linux-gcc (GCC) 16.1.0
smatch: v0.5.0-9187-g5189e3fb
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260828/[email protected]/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 <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All error/warnings (new ones prefixed by >>):

   In file included from include/linux/psi_types.h:5,
                    from include/linux/cgroup-defs.h:24,
                    from include/linux/cgroup.h:29,
                    from include/linux/memcontrol.h:13,
                    from include/linux/damon.h:10,
                    from mm/damon/core.c:8:
   mm/damon/core.c: In function '__damon_start':
>> mm/damon/core.c:1941:44: error: 'kdamond_fn' undeclared (first use in this function)
    1941 |                 ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
         |                                            ^~~~~~~~~~
   include/linux/kthread.h:46:32: note: in definition of macro 'kthread_create'
      46 |         kthread_create_on_node(threadfn, data, NUMA_NO_NODE, namefmt, ##arg)
         |                                ^~~~~~~~
   mm/damon/core.c:1941:32: note: in expansion of macro 'kthread_run'
    1941 |                 ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
         |                                ^~~~~~~~~~~
   mm/damon/core.c:1941:44: note: each undeclared identifier is reported only once for each function it appears in
   include/linux/kthread.h:46:32: note: in definition of macro 'kthread_create'
      46 |         kthread_create_on_node(threadfn, data, NUMA_NO_NODE, namefmt, ##arg)
         |                                ^~~~~~~~
   mm/damon/core.c:1941:32: note: in expansion of macro 'kthread_run'
    1941 |                 ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
         |                                ^~~~~~~~~~~
   mm/damon/core.c: At top level:
>> mm/damon/core.c:3750:12: warning: 'kdamond_fn' defined but not used [-Wunused-function]
    3750 | static int kdamond_fn(void *data)
         |            ^~~~~~~~~~


vim +/kdamond_fn +1941 mm/damon/core.c

b1029f29eb1d5fb SJ Park        2026-02-28  1924  
2224d8485492e49 SeongJae Park  2021-09-07  1925  /*
2224d8485492e49 SeongJae Park  2021-09-07  1926   * __damon_start() - Starts monitoring with given context.
2224d8485492e49 SeongJae Park  2021-09-07  1927   * @ctx:	monitoring context
2224d8485492e49 SeongJae Park  2021-09-07  1928   *
2224d8485492e49 SeongJae Park  2021-09-07  1929   * This function should be called while damon_lock is hold.
2224d8485492e49 SeongJae Park  2021-09-07  1930   *
2224d8485492e49 SeongJae Park  2021-09-07  1931   * Return: 0 on success, negative error code otherwise.
2224d8485492e49 SeongJae Park  2021-09-07  1932   */
2224d8485492e49 SeongJae Park  2021-09-07  1933  static int __damon_start(struct damon_ctx *ctx)
2224d8485492e49 SeongJae Park  2021-09-07  1934  {
2224d8485492e49 SeongJae Park  2021-09-07  1935  	int err = -EBUSY;
2224d8485492e49 SeongJae Park  2021-09-07  1936  
2224d8485492e49 SeongJae Park  2021-09-07  1937  	mutex_lock(&ctx->kdamond_lock);
2224d8485492e49 SeongJae Park  2021-09-07  1938  	if (!ctx->kdamond) {
2224d8485492e49 SeongJae Park  2021-09-07  1939  		err = 0;
6376a824595607e SJ Park        2023-12-08  1940  		reinit_completion(&ctx->kdamond_started);
2224d8485492e49 SeongJae Park  2021-09-07 @1941  		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
2224d8485492e49 SeongJae Park  2021-09-07  1942  				nr_running_ctxs);
2224d8485492e49 SeongJae Park  2021-09-07  1943  		if (IS_ERR(ctx->kdamond)) {
2224d8485492e49 SeongJae Park  2021-09-07  1944  			err = PTR_ERR(ctx->kdamond);
7ec1992b891e59d Colin Ian King 2021-11-05  1945  			ctx->kdamond = NULL;
6376a824595607e SJ Park        2023-12-08  1946  		} else {
6376a824595607e SJ Park        2023-12-08  1947  			wait_for_completion(&ctx->kdamond_started);
2224d8485492e49 SeongJae Park  2021-09-07  1948  		}
2224d8485492e49 SeongJae Park  2021-09-07  1949  	}
2224d8485492e49 SeongJae Park  2021-09-07  1950  	mutex_unlock(&ctx->kdamond_lock);
2224d8485492e49 SeongJae Park  2021-09-07  1951  
2224d8485492e49 SeongJae Park  2021-09-07  1952  	return err;
2224d8485492e49 SeongJae Park  2021-09-07  1953  }
2224d8485492e49 SeongJae Park  2021-09-07  1954  

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