From: Kairui Song <kasong@tencent.com> mainline inclusion from mainline-v6.13-rc6 commit 62e72d2cf702a5e2fb53d9c46ed900d9384e4a06 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IBMMCR Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Since commit 5abc1e37afa0 ("mm: list_lru: allocate list_lru_one only when needed"), all list_lru users need to allocate the items using the new infrastructure that provides list_lru info for slab allocation, ensuring that the corresponding memcg list_lru is allocated before use. For workingset shadow nodes (which are xa_node), users are converted to use the new infrastructure by commit 9bbdc0f32409 ("xarray: use kmem_cache_alloc_lru to allocate xa_node"). The xas->xa_lru will be set correctly for filemap users. However, there is a missing case: xa_node allocations caused by madvise(..., MADV_COLLAPSE). madvise(..., MADV_COLLAPSE) will also read in the absent parts of file map, and there will be xa_nodes allocated for the caller's memcg (assuming it's not rootcg). However, these allocations won't trigger memcg list_lru allocation because the proper xas info was not set. If nothing else has allocated other xa_nodes for that memcg to trigger list_lru creation, and memory pressure starts to evict file pages, workingset_update_node will try to add these xa_nodes to their corresponding memcg list_lru, and it does not exist (NULL). So they will be added to rootcg's list_lru instead. This shouldn't be a significant issue in practice, but it is indeed unexpected behavior, and these xa_nodes will not be reclaimed effectively. And may lead to incorrect counting of the list_lru->nr_items counter. This problem wasn't exposed until recent commit 28e98022b31ef ("mm/list_lru: simplify reparenting and initial allocation") added a sanity check: only dying memcg could have a NULL list_lru when list_lru_{add,del} is called. This problem triggered this WARNING. So make madvise(..., MADV_COLLAPSE) also call xas_set_lru() to pass the list_lru which we may want to insert xa_node into later. And move mapping_set_update to mm/internal.h, and turn into a macro to avoid including extra headers in mm/internal.h. Link: https://lkml.kernel.org/r/20241222122936.67501-1-ryncsn@gmail.com Fixes: 9bbdc0f32409 ("xarray: use kmem_cache_alloc_lru to allocate xa_node") Reported-by: syzbot+38a0cbd267eff2d286ff@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/675d01e9.050a0220.37aaf.00be.GAE@google.com/ Signed-off-by: Kairui Song <kasong@tencent.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Sasha Levin <sashal@kernel.org> Cc: Shakeel Butt <shakeel.butt@linux.dev> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: mm/khugepaged.c mm/internal.h mm/filemap.c [context conflicts] Signed-off-by: Kaixiong Yu <yukaixiong@huawei.com> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com> --- mm/filemap.c | 9 --------- mm/internal.h | 6 ++++++ mm/khugepaged.c | 3 +++ 3 files changed, 9 insertions(+), 9 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 004192a231cec..77a8947b8e5e5 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -128,15 +128,6 @@ * ->private_lock (zap_pte_range->block_dirty_folio) */ -static void mapping_set_update(struct xa_state *xas, - struct address_space *mapping) -{ - if (dax_mapping(mapping) || shmem_mapping(mapping)) - return; - xas_set_update(xas, workingset_update_node); - xas_set_lru(xas, &shadow_nodes); -} - static void page_cache_delete(struct address_space *mapping, struct folio *folio, void *shadow) { diff --git a/mm/internal.h b/mm/internal.h index fca749f0e0caa..2803e754c3e87 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1499,5 +1499,11 @@ void unlink_file_vma_batch_final(struct unlink_vma_file_batch *); /* Only track the nodes of mappings with shadow entries */ void workingset_update_node(struct xa_node *node); extern struct list_lru shadow_nodes; +#define mapping_set_update(xas, mapping) do { \ + if (!dax_mapping(mapping) && !shmem_mapping(mapping)) { \ + xas_set_update(xas, workingset_update_node); \ + xas_set_lru(xas, &shadow_nodes); \ + } \ +} while (0) #endif /* __MM_INTERNAL_H */ diff --git a/mm/khugepaged.c b/mm/khugepaged.c index f8eb225a89f93..2adeab4f66257 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -19,6 +19,7 @@ #include <linux/page_table_check.h> #include <linux/swapops.h> #include <linux/shmem_fs.h> +#include <linux/dax.h> #include <linux/ksm.h> #include <linux/dynamic_pool.h> @@ -1835,6 +1836,8 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, if (result != SCAN_SUCCEED) goto out; + mapping_set_update(&xas, mapping); + __folio_set_locked(new_folio); if (is_shmem) __folio_set_swapbacked(new_folio); -- 2.43.0