Re: [PATCH 2/2] mm: kfence: fix objcgs vector allocation

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

Hi Muchun,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on hnaz-mm/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Muchun-Song/mm-kfence-fix-missing-objcg-housekeeping-for-SLAB/20220327-132038
base:   https://github.com/hnaz/linux-mm master
config: x86_64-randconfig-c022 (https://download.01.org/0day-ci/archive/20220327/202203271619.Ni4lY7Mc-lkp@intel.com/config)
compiler: gcc-9 (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/a33cf78311711db98d9f77541d0a4b50bc466875
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Muchun-Song/mm-kfence-fix-missing-objcg-housekeeping-for-SLAB/20220327-132038
        git checkout a33cf78311711db98d9f77541d0a4b50bc466875
        # save the config file to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash mm/kfence/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   mm/kfence/core.c: In function 'kfence_init_pool':
>> mm/kfence/core.c:593:36: warning: passing argument 1 of 'virt_to_slab' makes pointer from integer without a cast [-Wint-conversion]
     593 |   struct slab *slab = virt_to_slab(addr);
         |                                    ^~~~
         |                                    |
         |                                    long unsigned int
   In file included from mm/kfence/kfence.h:17,
                    from mm/kfence/core.c:35:
   mm/kfence/../slab.h:173:53: note: expected 'const void *' but argument is of type 'long unsigned int'
     173 | static inline struct slab *virt_to_slab(const void *addr)
         |                                         ~~~~~~~~~~~~^~~~
   mm/kfence/core.c:597:7: error: 'struct slab' has no member named 'memcg_data'
     597 |   slab->memcg_data = (unsigned long)&meta->objcg | MEMCG_DATA_OBJCGS;
         |       ^~
   mm/kfence/core.c:597:52: error: 'MEMCG_DATA_OBJCGS' undeclared (first use in this function)
     597 |   slab->memcg_data = (unsigned long)&meta->objcg | MEMCG_DATA_OBJCGS;
         |                                                    ^~~~~~~~~~~~~~~~~
   mm/kfence/core.c:597:52: note: each undeclared identifier is reported only once for each function it appears in


vim +/virt_to_slab +593 mm/kfence/core.c

   543	
   544	/*
   545	 * Initialization of the KFENCE pool after its allocation.
   546	 * Returns 0 on success; otherwise returns the address up to
   547	 * which partial initialization succeeded.
   548	 */
   549	static unsigned long kfence_init_pool(void)
   550	{
   551		unsigned long addr = (unsigned long)__kfence_pool;
   552		struct page *pages;
   553		int i;
   554	
   555		if (!arch_kfence_init_pool())
   556			return addr;
   557	
   558		pages = virt_to_page(addr);
   559	
   560		/*
   561		 * Set up object pages: they must have PG_slab set, to avoid freeing
   562		 * these as real pages.
   563		 *
   564		 * We also want to avoid inserting kfence_free() in the kfree()
   565		 * fast-path in SLUB, and therefore need to ensure kfree() correctly
   566		 * enters __slab_free() slow-path.
   567		 */
   568		for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
   569			if (!i || (i % 2))
   570				continue;
   571	
   572			/* Verify we do not have a compound head page. */
   573			if (WARN_ON(compound_head(&pages[i]) != &pages[i]))
   574				return addr;
   575	
   576			__SetPageSlab(&pages[i]);
   577		}
   578	
   579		/*
   580		 * Protect the first 2 pages. The first page is mostly unnecessary, and
   581		 * merely serves as an extended guard page. However, adding one
   582		 * additional page in the beginning gives us an even number of pages,
   583		 * which simplifies the mapping of address to metadata index.
   584		 */
   585		for (i = 0; i < 2; i++) {
   586			if (unlikely(!kfence_protect(addr)))
   587				return addr;
   588	
   589			addr += PAGE_SIZE;
   590		}
   591	
   592		for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
 > 593			struct slab *slab = virt_to_slab(addr);
   594			struct kfence_metadata *meta = &kfence_metadata[i];
   595	
   596			/* Initialize metadata. */
   597			slab->memcg_data = (unsigned long)&meta->objcg | MEMCG_DATA_OBJCGS;
   598			INIT_LIST_HEAD(&meta->list);
   599			raw_spin_lock_init(&meta->lock);
   600			meta->state = KFENCE_OBJECT_UNUSED;
   601			meta->addr = addr; /* Initialize for validation in metadata_to_pageaddr(). */
   602			list_add_tail(&meta->list, &kfence_freelist);
   603	
   604			/* Protect the right redzone. */
   605			if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
   606				return addr;
   607	
   608			addr += 2 * PAGE_SIZE;
   609		}
   610	
   611		/*
   612		 * The pool is live and will never be deallocated from this point on.
   613		 * Remove the pool object from the kmemleak object tree, as it would
   614		 * otherwise overlap with allocations returned by kfence_alloc(), which
   615		 * are registered with kmemleak through the slab post-alloc hook.
   616		 */
   617		kmemleak_free(__kfence_pool);
   618	
   619		return 0;
   620	}
   621	

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