[android-common:android13-5.15-2026-06 6/6] mm/vmscan.c:905:15: warning: no previous prototype for 'shrink_slab'

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

Hi Peifeng,

FYI, the error/warning still remains.

tree:   https://android.googlesource.com/kernel/common android13-5.15-2026-06
head:   7e8c257a4ec10d7fb33263300a521590d71c1fb1
commit: 606b947630cb44c739336184df9ffd7d2cda34f3 [6/6] ANDROID: vendor_hooks: export shrink_slab
config: i386-randconfig-062-20260715 (https://download.01.org/0day-ci/archive/20260716/202607161757.POma50EB-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260716/202607161757.POma50EB-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/202607161757.POma50EB-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/vmscan.c:905:15: warning: no previous prototype for 'shrink_slab' [-Wmissing-prototypes]
     905 | unsigned long shrink_slab(gfp_t gfp_mask, int nid,
         |               ^~~~~~~~~~~
   mm/vmscan.c: In function 'demote_page_list':
   mm/vmscan.c:1357:13: warning: variable 'err' set but not used [-Wunused-but-set-variable]
    1357 |         int err;
         |             ^~~

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for ARCH_HAS_NONLEAF_PMD_YOUNG
   Depends on [n]: PGTABLE_LEVELS [=2]>2
   Selected by [y]:
   - X86 [=y]


vim +/shrink_slab +905 mm/vmscan.c

   884	
   885	/**
   886	 * shrink_slab - shrink slab caches
   887	 * @gfp_mask: allocation context
   888	 * @nid: node whose slab caches to target
   889	 * @memcg: memory cgroup whose slab caches to target
   890	 * @priority: the reclaim priority
   891	 *
   892	 * Call the shrink functions to age shrinkable caches.
   893	 *
   894	 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
   895	 * unaware shrinkers will receive a node id of 0 instead.
   896	 *
   897	 * @memcg specifies the memory cgroup to target. Unaware shrinkers
   898	 * are called only if it is the root cgroup.
   899	 *
   900	 * @priority is sc->priority, we take the number of objects and >> by priority
   901	 * in order to get the scan target.
   902	 *
   903	 * Returns the number of reclaimed slab objects.
   904	 */
 > 905	unsigned long shrink_slab(gfp_t gfp_mask, int nid,
   906					 struct mem_cgroup *memcg,
   907					 int priority)
   908	{
   909		unsigned long ret, freed = 0;
   910		struct shrinker *shrinker;
   911	
   912		/*
   913		 * The root memcg might be allocated even though memcg is disabled
   914		 * via "cgroup_disable=memory" boot parameter.  This could make
   915		 * mem_cgroup_is_root() return false, then just run memcg slab
   916		 * shrink, but skip global shrink.  This may result in premature
   917		 * oom.
   918		 */
   919		if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
   920			return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
   921	
   922		if (!down_read_trylock(&shrinker_rwsem))
   923			goto out;
   924	
   925		list_for_each_entry(shrinker, &shrinker_list, list) {
   926			struct shrink_control sc = {
   927				.gfp_mask = gfp_mask,
   928				.nid = nid,
   929				.memcg = memcg,
   930			};
   931	
   932			ret = do_shrink_slab(&sc, shrinker, priority);
   933			if (ret == SHRINK_EMPTY)
   934				ret = 0;
   935			freed += ret;
   936			/*
   937			 * Bail out if someone want to register a new shrinker to
   938			 * prevent the registration from being stalled for long periods
   939			 * by parallel ongoing shrinking.
   940			 */
   941			if (rwsem_is_contended(&shrinker_rwsem)) {
   942				freed = freed ? : 1;
   943				break;
   944			}
   945		}
   946	
   947		up_read(&shrinker_rwsem);
   948	out:
   949		cond_resched();
   950		return freed;
   951	}
   952	EXPORT_SYMBOL_GPL(shrink_slab);
   953	

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