Re: [PATCH 8/8] mm/swap: reduce swap cache search space

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

Hi Kairui,

kernel test robot noticed the following build errors:

[auto build test ERROR on ceph-client/testing]
[also build test ERROR on ceph-client/for-linus trondmy-nfs/linux-next konis-nilfs2/upstream jaegeuk-f2fs/dev-test jaegeuk-f2fs/dev cifs/for-next linus/master v6.9-rc4]
[cannot apply to akpm-mm/mm-everything next-20240418]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kairui-Song/NFS-remove-nfs_page_lengthg-and-usage-of-page_index/20240418-001343
base:   https://github.com/ceph/ceph-client.git testing
patch link:    https://lore.kernel.org/r/20240417160842.76665-9-ryncsn%40gmail.com
patch subject: [PATCH 8/8] mm/swap: reduce swap cache search space
config: i386-buildonly-randconfig-002-20240419 (https://download.01.org/0day-ci/archive/20240419/202404190258.wljFnvCL-lkp@intel.com/config)
compiler: gcc-9 (Ubuntu 9.5.0-4ubuntu2) 9.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240419/202404190258.wljFnvCL-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/202404190258.wljFnvCL-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/huge_memory.c: In function '__split_huge_page':
>> mm/huge_memory.c:2906:12: error: implicit declaration of function 'swap_cache_index' [-Werror=implicit-function-declaration]
    2906 |   offset = swap_cache_index(folio->swap);
         |            ^~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/swap_cache_index +2906 mm/huge_memory.c

  2888	
  2889	static void __split_huge_page(struct page *page, struct list_head *list,
  2890			pgoff_t end, unsigned int new_order)
  2891	{
  2892		struct folio *folio = page_folio(page);
  2893		struct page *head = &folio->page;
  2894		struct lruvec *lruvec;
  2895		struct address_space *swap_cache = NULL;
  2896		unsigned long offset = 0;
  2897		int i, nr_dropped = 0;
  2898		unsigned int new_nr = 1 << new_order;
  2899		int order = folio_order(folio);
  2900		unsigned int nr = 1 << order;
  2901	
  2902		/* complete memcg works before add pages to LRU */
  2903		split_page_memcg(head, order, new_order);
  2904	
  2905		if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
> 2906			offset = swap_cache_index(folio->swap);
  2907			swap_cache = swap_address_space(folio->swap);
  2908			xa_lock(&swap_cache->i_pages);
  2909		}
  2910	
  2911		/* lock lru list/PageCompound, ref frozen by page_ref_freeze */
  2912		lruvec = folio_lruvec_lock(folio);
  2913	
  2914		ClearPageHasHWPoisoned(head);
  2915	
  2916		for (i = nr - new_nr; i >= new_nr; i -= new_nr) {
  2917			__split_huge_page_tail(folio, i, lruvec, list, new_order);
  2918			/* Some pages can be beyond EOF: drop them from page cache */
  2919			if (head[i].index >= end) {
  2920				struct folio *tail = page_folio(head + i);
  2921	
  2922				if (shmem_mapping(folio->mapping))
  2923					nr_dropped++;
  2924				else if (folio_test_clear_dirty(tail))
  2925					folio_account_cleaned(tail,
  2926						inode_to_wb(folio->mapping->host));
  2927				__filemap_remove_folio(tail, NULL);
  2928				folio_put(tail);
  2929			} else if (!PageAnon(page)) {
  2930				__xa_store(&folio->mapping->i_pages, head[i].index,
  2931						head + i, 0);
  2932			} else if (swap_cache) {
  2933				__xa_store(&swap_cache->i_pages, offset + i,
  2934						head + i, 0);
  2935			}
  2936		}
  2937	
  2938		if (!new_order)
  2939			ClearPageCompound(head);
  2940		else {
  2941			struct folio *new_folio = (struct folio *)head;
  2942	
  2943			folio_set_order(new_folio, new_order);
  2944		}
  2945		unlock_page_lruvec(lruvec);
  2946		/* Caller disabled irqs, so they are still disabled here */
  2947	
  2948		split_page_owner(head, order, new_order);
  2949	
  2950		/* See comment in __split_huge_page_tail() */
  2951		if (folio_test_anon(folio)) {
  2952			/* Additional pin to swap cache */
  2953			if (folio_test_swapcache(folio)) {
  2954				folio_ref_add(folio, 1 + new_nr);
  2955				xa_unlock(&swap_cache->i_pages);
  2956			} else {
  2957				folio_ref_inc(folio);
  2958			}
  2959		} else {
  2960			/* Additional pin to page cache */
  2961			folio_ref_add(folio, 1 + new_nr);
  2962			xa_unlock(&folio->mapping->i_pages);
  2963		}
  2964		local_irq_enable();
  2965	
  2966		if (nr_dropped)
  2967			shmem_uncharge(folio->mapping->host, nr_dropped);
  2968		remap_page(folio, nr);
  2969	
  2970		if (folio_test_swapcache(folio))
  2971			split_swap_cluster(folio->swap);
  2972	
  2973		/*
  2974		 * set page to its compound_head when split to non order-0 pages, so
  2975		 * we can skip unlocking it below, since PG_locked is transferred to
  2976		 * the compound_head of the page and the caller will unlock it.
  2977		 */
  2978		if (new_order)
  2979			page = compound_head(page);
  2980	
  2981		for (i = 0; i < nr; i += new_nr) {
  2982			struct page *subpage = head + i;
  2983			struct folio *new_folio = page_folio(subpage);
  2984			if (subpage == page)
  2985				continue;
  2986			folio_unlock(new_folio);
  2987	
  2988			/*
  2989			 * Subpages may be freed if there wasn't any mapping
  2990			 * like if add_to_swap() is running on a lru page that
  2991			 * had its mapping zapped. And freeing these pages
  2992			 * requires taking the lru_lock so we do the put_page
  2993			 * of the tail pages after the split is complete.
  2994			 */
  2995			free_page_and_swap_cache(subpage);
  2996		}
  2997	}
  2998	

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