linux-kernel - mm/slub.c:2142:15: warning: variable 'partial

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Date: Sat, 6 Jan 2024 15:53:49 +0800
From: kernel test robot <lkp@...el.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org, Roman Gushchin <guro@...com>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>
Subject: mm/slub.c:2142:15: warning: variable 'partial_slabs' set but not used

Hi Vlastimil,

FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   95c8a35f1c017327eab3b6a2ff5c04255737c856
commit: bb192ed9aa7191a5d65548f82c42b6750d65f569 mm/slub: Convert most struct page to struct slab by spatch
date:   2 years ago
config: i386-allnoconfig (https://download.01.org/0day-ci/archive/20240106/202401061535.b3xgfK51-lkp@intel.com/config)
compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240106/202401061535.b3xgfK51-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401061535.b3xgfK51-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> mm/slub.c:2142:15: warning: variable 'partial_slabs' set but not used [-Wunused-but-set-variable]
    2142 |         unsigned int partial_slabs = 0;
         |                      ^
   mm/slub.c:1681:21: warning: unused function 'kmalloc_large_node_hook' [-Wunused-function]
    1681 | static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
         |                     ^~~~~~~~~~~~~~~~~~~~~~~
   2 warnings generated.


vim +/partial_slabs +2142 mm/slub.c

  2132	
  2133	/*
  2134	 * Try to allocate a partial slab from a specific node.
  2135	 */
  2136	static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
  2137				      struct slab **ret_slab, gfp_t gfpflags)
  2138	{
  2139		struct slab *slab, *slab2;
  2140		void *object = NULL;
  2141		unsigned long flags;
> 2142		unsigned int partial_slabs = 0;
  2143	
  2144		/*
  2145		 * Racy check. If we mistakenly see no partial slabs then we
  2146		 * just allocate an empty slab. If we mistakenly try to get a
  2147		 * partial slab and there is none available then get_partial()
  2148		 * will return NULL.
  2149		 */
  2150		if (!n || !n->nr_partial)
  2151			return NULL;
  2152	
  2153		spin_lock_irqsave(&n->list_lock, flags);
  2154		list_for_each_entry_safe(slab, slab2, &n->partial, slab_list) {
  2155			void *t;
  2156	
  2157			if (!pfmemalloc_match(slab, gfpflags))
  2158				continue;
  2159	
  2160			t = acquire_slab(s, n, slab, object == NULL);
  2161			if (!t)
  2162				break;
  2163	
  2164			if (!object) {
  2165				*ret_slab = slab;
  2166				stat(s, ALLOC_FROM_PARTIAL);
  2167				object = t;
  2168			} else {
  2169				put_cpu_partial(s, slab, 0);
  2170				stat(s, CPU_PARTIAL_NODE);
  2171				partial_slabs++;
  2172			}
  2173	#ifdef CONFIG_SLUB_CPU_PARTIAL
  2174			if (!kmem_cache_has_cpu_partial(s)
  2175				|| partial_slabs > s->cpu_partial_slabs / 2)
  2176				break;
  2177	#else
  2178			break;
  2179	#endif
  2180	
  2181		}
  2182		spin_unlock_irqrestore(&n->list_lock, flags);
  2183		return object;
  2184	}
  2185	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki