* Re: [PATCH] mm/huge_memory.c: introduce folio_split_unmapped
[not found] <20251114012228.2634882-1-balbirs@nvidia.com>
@ 2025-11-15 2:15 ` kernel test robot
2025-11-15 2:33 ` Balbir Singh
0 siblings, 1 reply; 3+ messages in thread
From: kernel test robot @ 2025-11-15 2:15 UTC (permalink / raw)
To: Balbir Singh, linux-kernel, linux-mm, dri-devel
Cc: llvm, oe-kbuild-all, Balbir Singh, Andrew Morton,
Linux Memory Management List, David Hildenbrand, Zi Yan,
Joshua Hahn, Rakie Kim, Byungchul Park, Gregory Price, Ying Huang,
Alistair Popple, Oscar Salvador, Lorenzo Stoakes, Baolin Wang,
Liam R. Howlett, Nico Pache, Ryan Roberts, Dev Jain, Barry Song,
Lyude Paul, Danilo Krummrich, David Airlie, Simona Vetter,
Ralph Campbell, Mika Penttilä, Matthew Brost,
Francois Dugast
Hi Balbir,
kernel test robot noticed the following build warnings:
[auto build test WARNING on akpm-mm/mm-everything]
url: https://github.com/intel-lab-lkp/linux/commits/Balbir-Singh/mm-huge_memory-c-introduce-folio_split_unmapped/20251114-093541
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20251114012228.2634882-1-balbirs%40nvidia.com
patch subject: [PATCH] mm/huge_memory.c: introduce folio_split_unmapped
config: arm64-randconfig-002-20251115 (https://download.01.org/0day-ci/archive/20251115/202511151007.F1gixfc8-lkp@intel.com/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251115/202511151007.F1gixfc8-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/202511151007.F1gixfc8-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> mm/huge_memory.c:3751:6: warning: variable 'nr_shmem_dropped' set but not used [-Wunused-but-set-variable]
3751 | int nr_shmem_dropped = 0;
| ^
1 warning generated.
vim +/nr_shmem_dropped +3751 mm/huge_memory.c
3741
3742 static int __folio_freeze_and_split_unmapped(struct folio *folio, unsigned int new_order,
3743 struct page *split_at, struct xa_state *xas,
3744 struct address_space *mapping, bool do_lru,
3745 struct list_head *list, enum split_type split_type,
3746 pgoff_t end, int extra_pins)
3747 {
3748 struct folio *end_folio = folio_next(folio);
3749 struct folio *new_folio, *next;
3750 int old_order = folio_order(folio);
> 3751 int nr_shmem_dropped = 0;
3752 int ret = 0;
3753 struct deferred_split *ds_queue;
3754
3755 /* Prevent deferred_split_scan() touching ->_refcount */
3756 ds_queue = folio_split_queue_lock(folio);
3757 if (folio_ref_freeze(folio, 1 + extra_pins)) {
3758 struct swap_cluster_info *ci = NULL;
3759 struct lruvec *lruvec;
3760 int expected_refs;
3761
3762 if (old_order > 1) {
3763 if (!list_empty(&folio->_deferred_list)) {
3764 ds_queue->split_queue_len--;
3765 /*
3766 * Reinitialize page_deferred_list after removing the
3767 * page from the split_queue, otherwise a subsequent
3768 * split will see list corruption when checking the
3769 * page_deferred_list.
3770 */
3771 list_del_init(&folio->_deferred_list);
3772 }
3773 if (folio_test_partially_mapped(folio)) {
3774 folio_clear_partially_mapped(folio);
3775 mod_mthp_stat(old_order,
3776 MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
3777 }
3778 }
3779 split_queue_unlock(ds_queue);
3780 if (mapping) {
3781 int nr = folio_nr_pages(folio);
3782
3783 if (folio_test_pmd_mappable(folio) &&
3784 new_order < HPAGE_PMD_ORDER) {
3785 if (folio_test_swapbacked(folio)) {
3786 __lruvec_stat_mod_folio(folio,
3787 NR_SHMEM_THPS, -nr);
3788 } else {
3789 __lruvec_stat_mod_folio(folio,
3790 NR_FILE_THPS, -nr);
3791 filemap_nr_thps_dec(mapping);
3792 }
3793 }
3794 }
3795
3796 if (folio_test_swapcache(folio)) {
3797 if (mapping) {
3798 VM_WARN_ON_ONCE_FOLIO(mapping, folio);
3799 return -EINVAL;
3800 }
3801
3802 ci = swap_cluster_get_and_lock(folio);
3803 }
3804
3805 /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
3806 if (do_lru)
3807 lruvec = folio_lruvec_lock(folio);
3808
3809 ret = __split_unmapped_folio(folio, new_order, split_at, xas,
3810 mapping, split_type);
3811
3812 /*
3813 * Unfreeze after-split folios and put them back to the right
3814 * list. @folio should be kept frozon until page cache
3815 * entries are updated with all the other after-split folios
3816 * to prevent others seeing stale page cache entries.
3817 * As a result, new_folio starts from the next folio of
3818 * @folio.
3819 */
3820 for (new_folio = folio_next(folio); new_folio != end_folio;
3821 new_folio = next) {
3822 unsigned long nr_pages = folio_nr_pages(new_folio);
3823
3824 next = folio_next(new_folio);
3825
3826 zone_device_private_split_cb(folio, new_folio);
3827
3828 expected_refs = folio_expected_ref_count(new_folio) + 1;
3829 folio_ref_unfreeze(new_folio, expected_refs);
3830
3831 if (do_lru)
3832 lru_add_split_folio(folio, new_folio, lruvec, list);
3833
3834 /*
3835 * Anonymous folio with swap cache.
3836 * NOTE: shmem in swap cache is not supported yet.
3837 */
3838 if (ci) {
3839 __swap_cache_replace_folio(ci, folio, new_folio);
3840 continue;
3841 }
3842
3843 /* Anonymous folio without swap cache */
3844 if (!mapping)
3845 continue;
3846
3847 /* Add the new folio to the page cache. */
3848 if (new_folio->index < end) {
3849 __xa_store(&mapping->i_pages, new_folio->index,
3850 new_folio, 0);
3851 continue;
3852 }
3853
3854 /* Drop folio beyond EOF: ->index >= end */
3855 if (shmem_mapping(mapping))
3856 nr_shmem_dropped += nr_pages;
3857 else if (folio_test_clear_dirty(new_folio))
3858 folio_account_cleaned(
3859 new_folio, inode_to_wb(mapping->host));
3860 __filemap_remove_folio(new_folio, NULL);
3861 folio_put_refs(new_folio, nr_pages);
3862 }
3863
3864 zone_device_private_split_cb(folio, NULL);
3865 /*
3866 * Unfreeze @folio only after all page cache entries, which
3867 * used to point to it, have been updated with new folios.
3868 * Otherwise, a parallel folio_try_get() can grab @folio
3869 * and its caller can see stale page cache entries.
3870 */
3871 expected_refs = folio_expected_ref_count(folio) + 1;
3872 folio_ref_unfreeze(folio, expected_refs);
3873
3874 if (do_lru)
3875 unlock_page_lruvec(lruvec);
3876
3877 if (ci)
3878 swap_cluster_unlock(ci);
3879 } else {
3880 split_queue_unlock(ds_queue);
3881 return -EAGAIN;
3882 }
3883
3884 return ret;
3885 }
3886
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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