Re: [PATCH v2] mm/mempolicy: track page allocations per mempolicy

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

Hi JP,

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/JP-Kobryn-Meta/mm-mempolicy-track-page-allocations-per-mempolicy/20260307-125642
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260307045520.247998-1-jp.kobryn%40linux.dev
patch subject: [PATCH v2] mm/mempolicy: track page allocations per mempolicy
config: x86_64-randconfig-074-20260307 (https://download.01.org/0day-ci/archive/20260307/202603072210.TSPUKsyq-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260307/202603072210.TSPUKsyq-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/202603072210.TSPUKsyq-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/mempolicy.c: In function 'mpol_count_numa_alloc':
   mm/mempolicy.c:2489:17: error: implicit declaration of function 'mem_cgroup_from_task'; did you mean 'mem_cgroup_from_css'? [-Wimplicit-function-declaration]
    2489 |         memcg = mem_cgroup_from_task(current);
         |                 ^~~~~~~~~~~~~~~~~~~~
         |                 mem_cgroup_from_css
>> mm/mempolicy.c:2489:15: error: assignment to 'struct mem_cgroup *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
    2489 |         memcg = mem_cgroup_from_task(current);
         |               ^


vim +2489 mm/mempolicy.c

  2429	
  2430	/*
  2431	 * Count a mempolicy allocation. Stats are tracked per-node and per-cgroup.
  2432	 * The following numa_{hit/miss/foreign} pattern is used:
  2433	 *
  2434	 *   hit
  2435	 *     - for BIND and PREFERRED_MANY, allocation succeeded on node in nodemask
  2436	 *     - for other policies, allocation succeeded on intended node
  2437	 *     - counted on the node of the allocation
  2438	 *   miss
  2439	 *     - allocation intended for other node, but happened on this one
  2440	 *     - counted on other node
  2441	 *   foreign
  2442	 *     - allocation intended on this node, but happened on other node
  2443	 *     - counted on this node
  2444	 */
  2445	static void mpol_count_numa_alloc(struct mempolicy *pol, int intended_nid,
  2446					  struct page *page, unsigned int order)
  2447	{
  2448		int actual_nid = page_to_nid(page);
  2449		long nr_pages = 1L << order;
  2450		enum node_stat_item hit_idx;
  2451		struct mem_cgroup *memcg;
  2452		struct lruvec *lruvec;
  2453		bool is_hit;
  2454	
  2455		if (!root_mem_cgroup || mem_cgroup_disabled())
  2456			return;
  2457	
  2458		/*
  2459		 * Start with hit then use +1 or +2 later on to change to miss or
  2460		 * foreign respectively if needed.
  2461		 */
  2462		switch (pol->mode) {
  2463		case MPOL_PREFERRED:
  2464			hit_idx = NUMA_MPOL_PREFERRED_HIT;
  2465			break;
  2466		case MPOL_PREFERRED_MANY:
  2467			hit_idx = NUMA_MPOL_PREFERRED_MANY_HIT;
  2468			break;
  2469		case MPOL_BIND:
  2470			hit_idx = NUMA_MPOL_BIND_HIT;
  2471			break;
  2472		case MPOL_INTERLEAVE:
  2473			hit_idx = NUMA_MPOL_INTERLEAVE_HIT;
  2474			break;
  2475		case MPOL_WEIGHTED_INTERLEAVE:
  2476			hit_idx = NUMA_MPOL_WEIGHTED_INTERLEAVE_HIT;
  2477			break;
  2478		default:
  2479			hit_idx = NUMA_MPOL_LOCAL_HIT;
  2480			break;
  2481		}
  2482	
  2483		if (pol->mode == MPOL_BIND || pol->mode == MPOL_PREFERRED_MANY)
  2484			is_hit = node_isset(actual_nid, pol->nodes);
  2485		else
  2486			is_hit = (actual_nid == intended_nid);
  2487	
  2488		rcu_read_lock();
> 2489		memcg = mem_cgroup_from_task(current);
  2490	
  2491		if (is_hit) {
  2492			lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(actual_nid));
  2493			mod_lruvec_state(lruvec, hit_idx, nr_pages);
  2494		} else {
  2495			/* account for miss on the fallback node */
  2496			lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(actual_nid));
  2497			mod_lruvec_state(lruvec, hit_idx + 1, nr_pages);
  2498	
  2499			/* account for foreign on the intended node */
  2500			lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(intended_nid));
  2501			mod_lruvec_state(lruvec, hit_idx + 2, nr_pages);
  2502		}
  2503	
  2504		rcu_read_unlock();
  2505	}
  2506	

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