From: Roman Gushchin guro@fb.com

Patch series "mm: allow mapping accounted kernel pages to userspace", v6.

Currently a non-slab kernel page which has been charged to a memory cgroup can't be mapped to userspace. The underlying reason is simple: PageKmemcg flag is defined as a page type (like buddy, offline, etc), so it takes a bit from a page->mapped counter. Pages with a type set can't be mapped to userspace.

But in general the kmemcg flag has nothing to do with mapping to userspace. It only means that the page has been accounted by the page allocator, so it has to be properly uncharged on release.

Some bpf maps are mapping the vmalloc-based memory to userspace, and their memory can't be accounted because of this implementation detail.

This patchset removes this limitation by moving the PageKmemcg flag into one of the free bits of the page->mem_cgroup pointer. Also it formalizes accesses to the page->mem_cgroup and page->obj_cgroups using new helpers, adds several checks and removes a couple of obsolete functions. As the result the code became more robust with fewer open-coded bit tricks.

This patch (of 4):

Currently there are many open-coded reads of the page->mem_cgroup pointer, as well as a couple of read helpers, which are barely used.

It creates an obstacle on a way to reuse some bits of the pointer for storing additional bits of information. In fact, we already do this for slab pages, where the last bit indicates that a pointer has an attached vector of objcg pointers instead of a regular memcg pointer.

This commits uses 2 existing helpers and introduces a new helper to converts all read sides to calls of these helpers: struct mem_cgroup *page_memcg(struct page *page); struct mem_cgroup *page_memcg_rcu(struct page *page); struct mem_cgroup *page_memcg_check(struct page *page);

page_memcg_check() is intended to be used in cases when the page can be a slab page and have a memcg pointer pointing at objcg vector. It does check the lowest bit, and if set, returns NULL. page_memcg() contains a VM_BUG_ON_PAGE() check for the page not being a slab page.

To make sure nobody uses a direct access, struct page's mem_cgroup/obj_cgroups is converted to unsigned long memcg_data.

Signed-off-by: Roman Gushchin guro@fb.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Alexei Starovoitov ast@kernel.org Reviewed-by: Shakeel Butt shakeelb@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Michal Hocko mhocko@suse.com Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com

Conflicts: mm/memcontrol.c Signed-off-by: Chen Huang chenhuang5@huawei.com --- fs/buffer.c | 2 +- fs/iomap/buffered-io.c | 2 +- include/linux/memcontrol.h | 114 ++++++++++++++++++++++++++--- include/linux/mm.h | 22 ------ include/linux/mm_types.h | 5 +- include/trace/events/writeback.h | 2 +- kernel/fork.c | 7 +- mm/debug.c | 4 +- mm/huge_memory.c | 4 +- mm/memcontrol.c | 122 ++++++++++++++----------------- mm/page_alloc.c | 4 +- mm/page_io.c | 6 +- mm/slab.h | 9 +-- mm/workingset.c | 2 +- 14 files changed, 184 insertions(+), 121 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c index 23f645657488..b56f99f82b5b 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -657,7 +657,7 @@ int __set_page_dirty_buffers(struct page *page) } while (bh != head); } /* - * Lock out page->mem_cgroup migration to keep PageDirty + * Lock out page's memcg migration to keep PageDirty * synchronized with per-memcg dirty page counters. */ lock_page_memcg(page); diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c index 10cc7979ce38..16a1e82e3aeb 100644 --- a/fs/iomap/buffered-io.c +++ b/fs/iomap/buffered-io.c @@ -650,7 +650,7 @@ iomap_set_page_dirty(struct page *page) return !TestSetPageDirty(page);

/* - * Lock out page->mem_cgroup migration to keep PageDirty + * Lock out page's memcg migration to keep PageDirty * synchronized with per-memcg dirty page counters. */ lock_page_memcg(page); diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index c691b1ac95f8..e3abc814f01b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -343,6 +343,79 @@ struct mem_cgroup {

extern struct mem_cgroup *root_mem_cgroup;

+/* + * page_memcg - get the memory cgroup associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the memory cgroup associated with the page, + * or NULL. This function assumes that the page is known to have a + * proper memory cgroup pointer. It's not safe to call this function + * against some type of pages, e.g. slab pages or ex-slab pages. + * + * Any of the following ensures page and memcg binding stability: + * - the page lock + * - LRU isolation + * - lock_page_memcg() + * - exclusive reference + */ +static inline struct mem_cgroup *page_memcg(struct page *page) +{ + VM_BUG_ON_PAGE(PageSlab(page), page); + return (struct mem_cgroup *)page->memcg_data; +} + +/* + * page_memcg_rcu - locklessly get the memory cgroup associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the memory cgroup associated with the page, + * or NULL. This function assumes that the page is known to have a + * proper memory cgroup pointer. It's not safe to call this function + * against some type of pages, e.g. slab pages or ex-slab pages. + */ +static inline struct mem_cgroup *page_memcg_rcu(struct page *page) +{ + VM_BUG_ON_PAGE(PageSlab(page), page); + WARN_ON_ONCE(!rcu_read_lock_held()); + + return (struct mem_cgroup *)READ_ONCE(page->memcg_data); +} + +/* + * page_memcg_check - get the memory cgroup associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the memory cgroup associated with the page, + * or NULL. This function unlike page_memcg() can take any page + * as an argument. It has to be used in cases when it's not known if a page + * has an associated memory cgroup pointer or an object cgroups vector. + * + * Any of the following ensures page and memcg binding stability: + * - the page lock + * - LRU isolation + * - lock_page_memcg() + * - exclusive reference + */ +static inline struct mem_cgroup *page_memcg_check(struct page *page) +{ + /* + * Because page->memcg_data might be changed asynchronously + * for slab pages, READ_ONCE() should be used here. + */ + unsigned long memcg_data = READ_ONCE(page->memcg_data); + + /* + * The lowest bit set means that memcg isn't a valid + * memcg pointer, but a obj_cgroups pointer. + * In this case the page is shared and doesn't belong + * to any specific memory cgroup. + */ + if (memcg_data & 0x1UL) + return NULL; + + return (struct mem_cgroup *)memcg_data; +} + static __always_inline bool memcg_stat_item_in_bytes(int idx) { if (idx == MEMCG_PERCPU_B) @@ -743,15 +816,19 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg, static inline void __mod_memcg_page_state(struct page *page, int idx, int val) { - if (page->mem_cgroup) - __mod_memcg_state(page->mem_cgroup, idx, val); + struct mem_cgroup *memcg = page_memcg(page); + + if (memcg) + __mod_memcg_state(memcg, idx, val); }

static inline void mod_memcg_page_state(struct page *page, int idx, int val) { - if (page->mem_cgroup) - mod_memcg_state(page->mem_cgroup, idx, val); + struct mem_cgroup *memcg = page_memcg(page); + + if (memcg) + mod_memcg_state(memcg, idx, val); }

static inline unsigned long lruvec_page_state(struct lruvec *lruvec, @@ -834,16 +911,17 @@ static inline void __mod_lruvec_page_state(struct page *page, enum node_stat_item idx, int val) { struct page *head = compound_head(page); /* rmap on tail pages */ + struct mem_cgroup *memcg = page_memcg(head); pg_data_t *pgdat = page_pgdat(page); struct lruvec *lruvec;

/* Untracked pages have no memcg, no lruvec. Update only the node */ - if (!head->mem_cgroup) { + if (!memcg) { __mod_node_page_state(pgdat, idx, val); return; }

- lruvec = mem_cgroup_lruvec(head->mem_cgroup, pgdat); + lruvec = mem_cgroup_lruvec(memcg, pgdat); __mod_lruvec_state(lruvec, idx, val); }

@@ -878,8 +956,10 @@ static inline void count_memcg_events(struct mem_cgroup *memcg, static inline void count_memcg_page_event(struct page *page, enum vm_event_item idx) { - if (page->mem_cgroup) - count_memcg_events(page->mem_cgroup, idx, 1); + struct mem_cgroup *memcg = page_memcg(page); + + if (memcg) + count_memcg_events(memcg, idx, 1); }

static inline void count_memcg_event_mm(struct mm_struct *mm, @@ -946,6 +1026,22 @@ void split_page_memcg(struct page *head, unsigned int nr);

struct mem_cgroup;

+static inline struct mem_cgroup *page_memcg(struct page *page) +{ + return NULL; +} + +static inline struct mem_cgroup *page_memcg_rcu(struct page *page) +{ + WARN_ON_ONCE(!rcu_read_lock_held()); + return NULL; +} + +static inline struct mem_cgroup *page_memcg_check(struct page *page) +{ + return NULL; +} + static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg) { return true; @@ -1435,7 +1531,7 @@ static inline void mem_cgroup_track_foreign_dirty(struct page *page, if (mem_cgroup_disabled()) return;

- if (unlikely(&page->mem_cgroup->css != wb->memcg_css)) + if (unlikely(&page_memcg(page)->css != wb->memcg_css)) mem_cgroup_track_foreign_dirty_slowpath(page, wb); }

diff --git a/include/linux/mm.h b/include/linux/mm.h index 289c26f055cd..fd5b9992d5d5 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1497,28 +1497,6 @@ static inline void set_page_links(struct page *page, enum zone_type zone, #endif }

-#ifdef CONFIG_MEMCG -static inline struct mem_cgroup *page_memcg(struct page *page) -{ - return page->mem_cgroup; -} -static inline struct mem_cgroup *page_memcg_rcu(struct page *page) -{ - WARN_ON_ONCE(!rcu_read_lock_held()); - return READ_ONCE(page->mem_cgroup); -} -#else -static inline struct mem_cgroup *page_memcg(struct page *page) -{ - return NULL; -} -static inline struct mem_cgroup *page_memcg_rcu(struct page *page) -{ - WARN_ON_ONCE(!rcu_read_lock_held()); - return NULL; -} -#endif - /* * Some inline functions in vmstat.h depend on page_zone() */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 4eb38918da8f..6733abbe7846 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -201,10 +201,7 @@ struct page { atomic_t _refcount;

#ifdef CONFIG_MEMCG - union { - struct mem_cgroup *mem_cgroup; - struct obj_cgroup **obj_cgroups; - }; + unsigned long memcg_data; #endif

/* diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h index 57d795365987..1efa463c4979 100644 --- a/include/trace/events/writeback.h +++ b/include/trace/events/writeback.h @@ -257,7 +257,7 @@ TRACE_EVENT(track_foreign_dirty, __entry->ino = inode ? inode->i_ino : 0; __entry->memcg_id = wb->memcg_css->id; __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); - __entry->page_cgroup_ino = cgroup_ino(page->mem_cgroup->css.cgroup); + __entry->page_cgroup_ino = cgroup_ino(page_memcg(page)->css.cgroup); ),

TP_printk("bdi %s[%llu]: ino=%lu memcg_id=%u cgroup_ino=%lu page_cgroup_ino=%lu", diff --git a/kernel/fork.c b/kernel/fork.c index 096945ef49ad..a668fc14f5a7 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -404,9 +404,10 @@ static int memcg_charge_kernel_stack(struct task_struct *tsk)

for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) { /* - * If memcg_kmem_charge_page() fails, page->mem_cgroup - * pointer is NULL, and memcg_kmem_uncharge_page() in - * free_thread_stack() will ignore this page. + * If memcg_kmem_charge_page() fails, page's + * memory cgroup pointer is NULL, and + * memcg_kmem_uncharge_page() in free_thread_stack() + * will ignore this page. */ ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0); diff --git a/mm/debug.c b/mm/debug.c index ccca576b2899..8a40b3fefbeb 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -182,8 +182,8 @@ void __dump_page(struct page *page, const char *reason) pr_warn("page dumped because: %s\n", reason);

#ifdef CONFIG_MEMCG - if (!page_poisoned && page->mem_cgroup) - pr_warn("page->mem_cgroup:%px\n", page->mem_cgroup); + if (!page_poisoned && page->memcg_data) + pr_warn("pages's memcg:%lx\n", page->memcg_data); #endif }

diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 594368f6134f..df4f0660a279 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -486,7 +486,7 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) #ifdef CONFIG_MEMCG static inline struct deferred_split *get_deferred_split_queue(struct page *page) { - struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(compound_head(page)); struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));

if (memcg) @@ -2784,7 +2784,7 @@ void deferred_split_huge_page(struct page *page) { struct deferred_split *ds_queue = get_deferred_split_queue(page); #ifdef CONFIG_MEMCG - struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(compound_head(page)); #endif unsigned long flags;

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 92bf987d0a41..dea907c83d40 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -533,7 +533,7 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page) { struct mem_cgroup *memcg;

- memcg = page->mem_cgroup; + memcg = page_memcg(page);

if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) memcg = root_mem_cgroup; @@ -560,16 +560,7 @@ ino_t page_cgroup_ino(struct page *page) unsigned long ino = 0;

rcu_read_lock(); - memcg = page->mem_cgroup; - - /* - * The lowest bit set means that memcg isn't a valid - * memcg pointer, but a obj_cgroups pointer. - * In this case the page is shared and doesn't belong - * to any specific memory cgroup. - */ - if ((unsigned long) memcg & 0x1UL) - memcg = NULL; + memcg = page_memcg_check(page);

while (memcg && !(memcg->css.flags & CSS_ONLINE)) memcg = parent_mem_cgroup(memcg); @@ -1055,7 +1046,7 @@ EXPORT_SYMBOL(get_mem_cgroup_from_mm); */ struct mem_cgroup *get_mem_cgroup_from_page(struct page *page) { - struct mem_cgroup *memcg = page->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(page);

if (mem_cgroup_disabled()) return NULL; @@ -1350,7 +1341,7 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd goto out; }

- memcg = page->mem_cgroup; + memcg = page_memcg(page); /* * Swapcache readahead pages are added to the LRU - and * possibly migrated - before they are charged. @@ -2110,7 +2101,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) }

/** - * lock_page_memcg - lock a page->mem_cgroup binding + * lock_page_memcg - lock a page and memcg binding * @page: the page * * This function protects unlocked LRU pages from being moved to @@ -2142,7 +2133,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page) if (mem_cgroup_disabled()) return NULL; again: - memcg = head->mem_cgroup; + memcg = page_memcg(head); if (unlikely(!memcg)) return NULL;

@@ -2150,7 +2141,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page) return memcg;

spin_lock_irqsave(&memcg->move_lock, flags); - if (memcg != head->mem_cgroup) { + if (memcg != page_memcg(head)) { spin_unlock_irqrestore(&memcg->move_lock, flags); goto again; } @@ -2188,14 +2179,14 @@ void __unlock_page_memcg(struct mem_cgroup *memcg) }

/** - * unlock_page_memcg - unlock a page->mem_cgroup binding + * unlock_page_memcg - unlock a page and memcg binding * @page: the page */ void unlock_page_memcg(struct page *page) { struct page *head = compound_head(page);

- __unlock_page_memcg(head->mem_cgroup); + __unlock_page_memcg(page_memcg(head)); } EXPORT_SYMBOL(unlock_page_memcg);

@@ -2885,7 +2876,7 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)

static void commit_charge(struct page *page, struct mem_cgroup *memcg) { - VM_BUG_ON_PAGE(page->mem_cgroup, page); + VM_BUG_ON_PAGE(page_memcg(page), page); /* * Any of the following ensures page->mem_cgroup stability: * @@ -2894,7 +2885,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg) * - lock_page_memcg() * - exclusive reference */ - page->mem_cgroup = memcg; + page->memcg_data = (unsigned long)memcg; }

#ifdef CONFIG_MEMCG_KMEM @@ -2917,8 +2908,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, if (!vec) return -ENOMEM;

- if (cmpxchg(&page->obj_cgroups, NULL, - (struct obj_cgroup **) ((unsigned long)vec | 0x1UL))) + if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL)) kfree(vec); else kmemleak_not_leak(vec); @@ -2929,6 +2919,12 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, /* * Returns a pointer to the memory cgroup to which the kernel object is charged. * + * A passed kernel object can be a slab object or a generic kernel page, so + * different mechanisms for getting the memory cgroup pointer should be used. + * In certain cases (e.g. kernel stacks or large kmallocs with SLUB) the caller + * can not know for sure how the kernel object is implemented. + * mem_cgroup_from_obj() can be safely used in such cases. + * * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(), * cgroup_mutex, etc. */ @@ -2941,17 +2937,6 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)

page = virt_to_head_page(p);

- /* - * If page->mem_cgroup is set, it's either a simple mem_cgroup pointer - * or a pointer to obj_cgroup vector. In the latter case the lowest - * bit of the pointer is set. - * The page->mem_cgroup pointer can be asynchronously changed - * from NULL to (obj_cgroup_vec | 0x1UL), but can't be changed - * from a valid memcg pointer to objcg vector or back. - */ - if (!page->mem_cgroup) - return NULL; - /* * Slab objects are accounted individually, not per-page. * Memcg membership data for each individual object is saved in @@ -2969,8 +2954,14 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p) return NULL; }

- /* All other pages use page->mem_cgroup */ - return page->mem_cgroup; + /* + * page_memcg_check() is used here, because page_has_obj_cgroups() + * check above could fail because the object cgroups vector wasn't set + * at that moment, but it can be set concurrently. + * page_memcg_check(page) will guarantee that a proper memory + * cgroup pointer or NULL will be returned. + */ + return page_memcg_check(page); }

__always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) @@ -3107,7 +3098,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order) if (memcg && !mem_cgroup_is_root(memcg)) { ret = __memcg_kmem_charge(memcg, gfp, 1 << order); if (!ret) { - page->mem_cgroup = memcg; + page->memcg_data = (unsigned long)memcg; __SetPageKmemcg(page); return 0; } @@ -3123,7 +3114,7 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order) */ void __memcg_kmem_uncharge_page(struct page *page, int order) { - struct mem_cgroup *memcg = page->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(page); unsigned int nr_pages = 1 << order;

if (!memcg) @@ -3131,7 +3122,7 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)

VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page); __memcg_kmem_uncharge(memcg, nr_pages); - page->mem_cgroup = NULL; + page->memcg_data = 0; css_put(&memcg->css);

/* slab pages do not have PageKmemcg flag set */ @@ -3289,15 +3280,14 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size) */ void split_page_memcg(struct page *head, unsigned int nr) { - struct mem_cgroup *memcg = head->mem_cgroup; - int kmemcg = PageKmemcg(head); + struct mem_cgroup *memcg = page_memcg(head); int i;

if (mem_cgroup_disabled() || !memcg) return;

for (i = 1; i < nr; i++) { - head[i].mem_cgroup = memcg; + head[i].memcg_data = (unsigned long)memcg; if (kmemcg) __SetPageKmemcg(head + i); } @@ -4681,7 +4671,7 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages, void mem_cgroup_track_foreign_dirty_slowpath(struct page *page, struct bdi_writeback *wb) { - struct mem_cgroup *memcg = page->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(page); struct memcg_cgwb_frn *frn; u64 now = get_jiffies_64(); u64 oldest_at = now; @@ -5658,14 +5648,14 @@ static int mem_cgroup_move_account(struct page *page,

/* * Prevent mem_cgroup_migrate() from looking at - * page->mem_cgroup of its source page while we change it. + * page's memory cgroup of its source page while we change it. */ ret = -EBUSY; if (!trylock_page(page)) goto out;

ret = -EINVAL; - if (page->mem_cgroup != from) + if (page_memcg(page) != from) goto out_unlock;

pgdat = page_pgdat(page); @@ -5718,13 +5708,13 @@ static int mem_cgroup_move_account(struct page *page, /* * All state has been migrated, let's switch to the new memcg. * - * It is safe to change page->mem_cgroup here because the page + * It is safe to change page's memcg here because the page * is referenced, charged, isolated, and locked: we can't race * with (un)charging, migration, LRU putback, or anything else - * that would rely on a stable page->mem_cgroup. + * that would rely on a stable page's memory cgroup. * * Note that lock_page_memcg is a memcg lock, not a page lock, - * to save space. As soon as we switch page->mem_cgroup to a + * to save space. As soon as we switch page's memory cgroup to a * new memcg that isn't locked, the above state can change * concurrently again. Make sure we're truly done with it. */ @@ -5733,7 +5723,7 @@ static int mem_cgroup_move_account(struct page *page, css_get(&to->css); css_put(&from->css);

- page->mem_cgroup = to; + page->memcg_data = (unsigned long)to;

__unlock_page_memcg(from);

@@ -5799,7 +5789,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma, * mem_cgroup_move_account() checks the page is valid or * not under LRU exclusion. */ - if (page->mem_cgroup == mc.from) { + if (page_memcg(page) == mc.from) { ret = MC_TARGET_PAGE; if (is_device_private_page(page)) ret = MC_TARGET_DEVICE; @@ -5843,7 +5833,7 @@ static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma, VM_BUG_ON_PAGE(!page || !PageHead(page), page); if (!(mc.flags & MOVE_ANON)) return ret; - if (page->mem_cgroup == mc.from) { + if (page_memcg(page) == mc.from) { ret = MC_TARGET_PAGE; if (target) { get_page(page); @@ -6788,12 +6778,12 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask) /* * Every swap fault against a single page tries to charge the * page, bail as early as possible. shmem_unuse() encounters - * already charged pages, too. page->mem_cgroup is protected - * by the page lock, which serializes swap cache removal, which - * in turn serializes uncharging. + * already charged pages, too. page and memcg binding is + * protected by the page lock, which serializes swap cache + * removal, which in turn serializes uncharging. */ VM_BUG_ON_PAGE(!PageLocked(page), page); - if (compound_head(page)->mem_cgroup) + if (page_memcg(compound_head(page))) goto out;

id = lookup_swap_cgroup_id(ent); @@ -6889,21 +6879,21 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)

VM_BUG_ON_PAGE(PageLRU(page), page);

- if (!page->mem_cgroup) + if (!page_memcg(page)) return;

/* * Nobody should be changing or seriously looking at - * page->mem_cgroup at this point, we have fully + * page_memcg(page) at this point, we have fully * exclusive access to the page. */

- if (ug->memcg != page->mem_cgroup) { + if (ug->memcg != page_memcg(page)) { if (ug->memcg) { uncharge_batch(ug); uncharge_gather_clear(ug); } - ug->memcg = page->mem_cgroup; + ug->memcg = page_memcg(page);

/* pairs with css_put in uncharge_batch */ css_get(&ug->memcg->css); @@ -6920,7 +6910,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) }

ug->dummy_page = page; - page->mem_cgroup = NULL; + page->memcg_data = 0; css_put(&ug->memcg->css); }

@@ -6963,7 +6953,7 @@ void mem_cgroup_uncharge(struct page *page) return;

/* Don't touch page->lru of any random page, pre-check: */ - if (!page->mem_cgroup) + if (!page_memcg(page)) return;

uncharge_gather_clear(&ug); @@ -7013,11 +7003,11 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage) return;

/* Page cache replacement: new page already charged? */ - if (newpage->mem_cgroup) + if (page_memcg(newpage)) return;

/* Swapcache readahead pages can get replaced before being charged */ - memcg = oldpage->mem_cgroup; + memcg = page_memcg(oldpage); if (!memcg) return;

@@ -7212,7 +7202,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) return;

- memcg = page->mem_cgroup; + memcg = page_memcg(page);

/* Readahead page, never charged */ if (!memcg) @@ -7233,7 +7223,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) VM_BUG_ON_PAGE(oldid, page); mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);

- page->mem_cgroup = NULL; + page->memcg_data = 0;

if (!mem_cgroup_is_root(memcg)) page_counter_uncharge(&memcg->memory, nr_entries); @@ -7276,7 +7266,7 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry) if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) return 0;

- memcg = page->mem_cgroup; + memcg = page_memcg(page);

/* Readahead page, never charged */ if (!memcg) @@ -7357,7 +7347,7 @@ bool mem_cgroup_swap_full(struct page *page) if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys)) return false;

- memcg = page->mem_cgroup; + memcg = page_memcg(page); if (!memcg) return false;

diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0166558d3d64..ef19a693721f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1094,7 +1094,7 @@ static inline bool page_expected_state(struct page *page, if (unlikely((unsigned long)page->mapping | page_ref_count(page) | #ifdef CONFIG_MEMCG - (unsigned long)page->mem_cgroup | + (unsigned long)page_memcg(page) | #endif (page->flags & check_flags))) return false; @@ -1119,7 +1119,7 @@ static const char *page_bad_reason(struct page *page, unsigned long flags) bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set"; } #ifdef CONFIG_MEMCG - if (unlikely(page->mem_cgroup)) + if (unlikely(page_memcg(page))) bad_reason = "page still charged to cgroup"; #endif return bad_reason; diff --git a/mm/page_io.c b/mm/page_io.c index 96479817ffae..21f3160d39a8 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -286,12 +286,14 @@ static inline void count_swpout_vm_event(struct page *page) static void bio_associate_blkg_from_page(struct bio *bio, struct page *page) { struct cgroup_subsys_state *css; + struct mem_cgroup *memcg;

- if (!page->mem_cgroup) + memcg = page_memcg(page); + if (!memcg) return;

rcu_read_lock(); - css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys); + css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys); bio_associate_blkg_from_css(bio, css); rcu_read_unlock(); } diff --git a/mm/slab.h b/mm/slab.h index 944e8b2040ae..ac43829b73d4 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -240,18 +240,17 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla static inline struct obj_cgroup **page_obj_cgroups(struct page *page) { /* - * page->mem_cgroup and page->obj_cgroups are sharing the same + * Page's memory cgroup and obj_cgroups vector are sharing the same * space. To distinguish between them in case we don't know for sure * that the page is a slab page (e.g. page_cgroup_ino()), let's * always set the lowest bit of obj_cgroups. */ - return (struct obj_cgroup **) - ((unsigned long)page->obj_cgroups & ~0x1UL); + return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); }

static inline bool page_has_obj_cgroups(struct page *page) { - return ((unsigned long)page->obj_cgroups & 0x1UL); + return page->memcg_data & 0x1UL; }

int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, @@ -260,7 +259,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, static inline void memcg_free_page_obj_cgroups(struct page *page) { kfree(page_obj_cgroups(page)); - page->obj_cgroups = NULL; + page->memcg_data = 0; }

static inline size_t obj_full_size(struct kmem_cache *s) diff --git a/mm/workingset.c b/mm/workingset.c index 975a4d2dd02e..130348cbf40a 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -257,7 +257,7 @@ void *workingset_eviction(struct page *page, struct mem_cgroup *target_memcg) struct lruvec *lruvec; int memcgid;

- /* Page is fully exclusive and pins page->mem_cgroup */ + /* Page is fully exclusive and pins page's memory cgroup pointer */ VM_BUG_ON_PAGE(PageLRU(page), page); VM_BUG_ON_PAGE(page_count(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page);

From: Roman Gushchin guro@fb.com

The lowest bit in page->memcg_data is used to distinguish between struct memory_cgroup pointer and a pointer to a objcgs array. All checks and modifications of this bit are open-coded.

Let's formalize it using page memcg flags, defined in enum page_memcg_data_flags.

Additional flags might be added later.

Signed-off-by: Roman Gushchin guro@fb.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Alexei Starovoitov ast@kernel.org Reviewed-by: Shakeel Butt shakeelb@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Michal Hocko mhocko@suse.com Link: https://lkml.kernel.org/r/20201027001657.3398190-4-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-4-guro@fb.com Signed-off-by: Chen Huang chenhuang5@huawei.com --- include/linux/memcontrol.h | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 2805fe81f97d..4a0feb9d4b82 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -343,6 +343,15 @@ struct mem_cgroup {

extern struct mem_cgroup *root_mem_cgroup;

+enum page_memcg_data_flags { + /* page->memcg_data is a pointer to an objcgs vector */ + MEMCG_DATA_OBJCGS = (1UL << 0), + /* the next bit after the last actual flag */ + __NR_MEMCG_DATA_FLAGS = (1UL << 1), +}; + +#define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1) + /* * page_memcg - get the memory cgroup associated with a page * @page: a pointer to the page struct @@ -404,13 +413,7 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) */ unsigned long memcg_data = READ_ONCE(page->memcg_data);

- /* - * The lowest bit set means that memcg isn't a valid - * memcg pointer, but a obj_cgroups pointer. - * In this case the page is shared and doesn't belong - * to any specific memory cgroup. - */ - if (memcg_data & 0x1UL) + if (memcg_data & MEMCG_DATA_OBJCGS) return NULL;

return (struct mem_cgroup *)memcg_data; @@ -429,7 +432,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) */ static inline struct obj_cgroup **page_objcgs(struct page *page) { - return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL); + unsigned long memcg_data = READ_ONCE(page->memcg_data); + + VM_BUG_ON_PAGE(memcg_data && !(memcg_data & MEMCG_DATA_OBJCGS), page); + + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); }

/* @@ -444,10 +451,10 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page) { unsigned long memcg_data = READ_ONCE(page->memcg_data);

- if (memcg_data && (memcg_data & 0x1UL)) - return (struct obj_cgroup **)(memcg_data & ~0x1UL); + if (!memcg_data || !(memcg_data & MEMCG_DATA_OBJCGS)) + return NULL;

- return NULL; + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); }

/* @@ -460,7 +467,8 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page) static inline bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs) { - return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL); + return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | + MEMCG_DATA_OBJCGS); } #else static inline struct obj_cgroup **page_objcgs(struct page *page)

From: Muchun Song songmuchun@bytedance.com

We know that the unit of slab object charging is bytes, the unit of kmem page charging is PAGE_SIZE. If we want to reuse obj_cgroup APIs to charge the kmem pages, we should pass PAGE_SIZE (as third parameter) to obj_cgroup_charge(). Because the size is already PAGE_SIZE, we can skip touch the objcg stock. And obj_cgroup_{un}charge_pages() are introduced to charge in units of page level.

In the latter patch, we also can reuse those two helpers to charge or uncharge a number of kernel pages to a object cgroup. This is just a code movement without any functional changes.

Link: https://lkml.kernel.org/r/20210319163821.20704-3-songmuchun@bytedance.com Signed-off-by: Muchun Song songmuchun@bytedance.com Acked-by: Roman Gushchin guro@fb.com Acked-by: Johannes Weiner hannes@cmpxchg.org Reviewed-by: Shakeel Butt shakeelb@google.com Cc: Michal Hocko mhocko@kernel.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Xiongchun Duan duanxiongchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Chen Huang chenhuang5@huawei.com --- mm/memcontrol.c | 63 +++++++++++++++++++++++++++++++------------------ 1 file changed, 40 insertions(+), 23 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index abeaf5cede74..d45c2c97d9b8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2888,6 +2888,20 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg) page->memcg_data = (unsigned long)memcg; }

+static struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg) +{ + struct mem_cgroup *memcg; + + rcu_read_lock(); +retry: + memcg = obj_cgroup_memcg(objcg); + if (unlikely(!css_tryget(&memcg->css))) + goto retry; + rcu_read_unlock(); + + return memcg; +} + #ifdef CONFIG_MEMCG_KMEM /* * The allocated objcg pointers array is not accounted directly. @@ -3032,6 +3046,29 @@ static void memcg_free_cache_id(int id) ida_simple_remove(&memcg_cache_ida, id); }

+static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg, + unsigned int nr_pages) +{ + struct mem_cgroup *memcg; + + memcg = get_mem_cgroup_from_objcg(objcg); + __memcg_kmem_uncharge(memcg, nr_pages); + css_put(&memcg->css); +} + +static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, + unsigned int nr_pages) +{ + struct mem_cgroup *memcg; + int ret; + + memcg = get_mem_cgroup_from_objcg(objcg); + ret = __memcg_kmem_charge(memcg, gfp, nr_pages); + css_put(&memcg->css); + + return ret; +} + /** * __memcg_kmem_charge: charge a number of kernel pages to a memcg * @memcg: memory cgroup to charge @@ -3156,19 +3193,8 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock) unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT; unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);

- if (nr_pages) { - struct mem_cgroup *memcg; - - rcu_read_lock(); -retry: - memcg = obj_cgroup_memcg(old); - if (unlikely(!css_tryget(&memcg->css))) - goto retry; - rcu_read_unlock(); - - __memcg_kmem_uncharge(memcg, nr_pages); - css_put(&memcg->css); - } + if (nr_pages) + obj_cgroup_uncharge_pages(old, nr_pages);

/* * The leftover is flushed to the centralized per-memcg value. @@ -3226,7 +3252,6 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)

int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size) { - struct mem_cgroup *memcg; unsigned int nr_pages, nr_bytes; int ret;

@@ -3243,24 +3268,16 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size) * refill_obj_stock(), called from this function or * independently later. */ - rcu_read_lock(); -retry: - memcg = obj_cgroup_memcg(objcg); - if (unlikely(!css_tryget(&memcg->css))) - goto retry; - rcu_read_unlock(); - nr_pages = size >> PAGE_SHIFT; nr_bytes = size & (PAGE_SIZE - 1);

if (nr_bytes) nr_pages += 1;

- ret = __memcg_kmem_charge(memcg, gfp, nr_pages); + ret = obj_cgroup_charge_pages(objcg, gfp, nr_pages); if (!ret && nr_bytes) refill_obj_stock(objcg, PAGE_SIZE - nr_bytes);

- css_put(&memcg->css); return ret; }

From: Muchun Song songmuchun@bytedance.com

Just like assignment to ug->memcg, we only need to update ug->dummy_page if memcg changed. So move it to there. This is a very small optimization.

Link: https://lkml.kernel.org/r/20210319163821.20704-5-songmuchun@bytedance.com Signed-off-by: Muchun Song songmuchun@bytedance.com Acked-by: Johannes Weiner hannes@cmpxchg.org Reviewed-by: Shakeel Butt shakeelb@google.com Cc: Michal Hocko mhocko@kernel.org Cc: Roman Gushchin guro@fb.com Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Xiongchun Duan duanxiongchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Chen Huang chenhuang5@huawei.com --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d45c2c97d9b8..73418413958c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6907,6 +6907,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) uncharge_gather_clear(ug); } ug->memcg = page_memcg(page); + ug->dummy_page = page;

/* pairs with css_put in uncharge_batch */ css_get(&ug->memcg->css); @@ -6920,7 +6921,6 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) else ug->pgpgout++;

- ug->dummy_page = page; page->memcg_data = 0; css_put(&ug->memcg->css); }

From: Muchun Song songmuchun@bytedance.com

There is only one user of __memcg_kmem_charge(), so manually inline __memcg_kmem_charge() to obj_cgroup_charge_pages(). Similarly manually inline __memcg_kmem_uncharge() into obj_cgroup_uncharge_pages() and call obj_cgroup_uncharge_pages() in obj_cgroup_release().

This is just code cleanup without any functionality changes.

Link: https://lkml.kernel.org/r/20210319163821.20704-7-songmuchun@bytedance.com Signed-off-by: Muchun Song songmuchun@bytedance.com Reviewed-by: Shakeel Butt shakeelb@google.com Acked-by: Roman Gushchin guro@fb.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Xiongchun Duan duanxiongchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

Conflicts: mm/memcontrol.c Signed-off-by: Chen Huang chenhuang5@huawei.com --- mm/memcontrol.c | 60 +++++++++++++++++++++---------------------------- 1 file changed, 26 insertions(+), 34 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 738051c79cdd..8932f986bf2e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -252,6 +252,9 @@ struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr) #ifdef CONFIG_MEMCG_KMEM extern spinlock_t css_set_lock;

+static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg, + unsigned int nr_pages); + static void obj_cgroup_release(struct percpu_ref *ref) { struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt); @@ -287,7 +290,7 @@ static void obj_cgroup_release(struct percpu_ref *ref) spin_lock_irqsave(&css_set_lock, flags); memcg = obj_cgroup_memcg(objcg); if (nr_pages) - __memcg_kmem_uncharge(memcg, nr_pages); + obj_cgroup_uncharge_pages(objcg, nr_pages); list_del(&objcg->list); mem_cgroup_put(memcg); spin_unlock_irqrestore(&css_set_lock, flags); @@ -3018,46 +3021,45 @@ static void memcg_free_cache_id(int id) ida_simple_remove(&memcg_cache_ida, id); }

+/* + * obj_cgroup_uncharge_pages: uncharge a number of kernel pages from a objcg + * @objcg: object cgroup to uncharge + * @nr_pages: number of pages to uncharge + */ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg, unsigned int nr_pages) { struct mem_cgroup *memcg;

memcg = get_mem_cgroup_from_objcg(objcg); - __memcg_kmem_uncharge(memcg, nr_pages); - css_put(&memcg->css); -}

-static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, - unsigned int nr_pages) -{ - struct mem_cgroup *memcg; - int ret; + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) + page_counter_uncharge(&memcg->kmem, nr_pages); + refill_stock(memcg, nr_pages);

- memcg = get_mem_cgroup_from_objcg(objcg); - ret = __memcg_kmem_charge(memcg, gfp, nr_pages); css_put(&memcg->css); - - return ret; }

-/** - * __memcg_kmem_charge: charge a number of kernel pages to a memcg - * @memcg: memory cgroup to charge +/* + * obj_cgroup_charge_pages: charge a number of kernel pages to a objcg + * @objcg: object cgroup to charge * @gfp: reclaim mode * @nr_pages: number of pages to charge * * Returns 0 on success, an error code on failure. */ -int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp, - unsigned int nr_pages) +static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, + unsigned int nr_pages) { struct page_counter *counter; + struct mem_cgroup *memcg; int ret;

+ memcg = get_mem_cgroup_from_objcg(objcg); + ret = try_charge(memcg, gfp, nr_pages); if (ret) - return ret; + goto out;

if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) { @@ -3069,25 +3071,15 @@ int __memcg_kmem_charge(struct mem_cgroup *memcg, gfp_t gfp, */ if (gfp & __GFP_NOFAIL) { page_counter_charge(&memcg->kmem, nr_pages); - return 0; + goto out; } cancel_charge(memcg, nr_pages); - return -ENOMEM; + ret = -ENOMEM; } - return 0; -} - -/** - * __memcg_kmem_uncharge: uncharge a number of kernel pages from a memcg - * @memcg: memcg to uncharge - * @nr_pages: number of pages to uncharge - */ -void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages) -{ - if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) - page_counter_uncharge(&memcg->kmem, nr_pages); +out: + css_put(&memcg->css);

- refill_stock(memcg, nr_pages); + return ret; }

/**

From: Wang Hai wanghai38@huawei.com

When I use kfree_rcu() to free a large memory allocated by kmalloc_node(), the following dump occurs.

BUG: kernel NULL pointer dereference, address: 0000000000000020 [...] Oops: 0000 [#1] SMP [...] Workqueue: events kfree_rcu_work RIP: 0010:__obj_to_index include/linux/slub_def.h:182 [inline] RIP: 0010:obj_to_index include/linux/slub_def.h:191 [inline] RIP: 0010:memcg_slab_free_hook+0x120/0x260 mm/slab.h:363 [...] Call Trace: kmem_cache_free_bulk+0x58/0x630 mm/slub.c:3293 kfree_bulk include/linux/slab.h:413 [inline] kfree_rcu_work+0x1ab/0x200 kernel/rcu/tree.c:3300 process_one_work+0x207/0x530 kernel/workqueue.c:2276 worker_thread+0x320/0x610 kernel/workqueue.c:2422 kthread+0x13d/0x160 kernel/kthread.c:313 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

When kmalloc_node() a large memory, page is allocated, not slab, so when freeing memory via kfree_rcu(), this large memory should not be used by memcg_slab_free_hook(), because memcg_slab_free_hook() is is used for slab.

Using page_objcgs_check() instead of page_objcgs() in memcg_slab_free_hook() to fix this bug.

Link: https://lkml.kernel.org/r/20210728145655.274476-1-wanghai38@huawei.com Fixes: 270c6a71460e ("mm: memcontrol/slab: Use helpers to access slab page's memcg_data") Signed-off-by: Wang Hai wanghai38@huawei.com Reviewed-by: Shakeel Butt shakeelb@google.com Acked-by: Michal Hocko mhocko@suse.com Acked-by: Roman Gushchin guro@fb.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Reviewed-by: Muchun Song songmuchun@bytedance.com Cc: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Johannes Weiner hannes@cmpxchg.org Cc: Alexei Starovoitov ast@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Chen Huang chenhuang5@huawei.com --- mm/slab.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab.h b/mm/slab.h index 571757eb4a8f..9759992c720c 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -349,7 +349,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, continue;

page = virt_to_head_page(p[i]); - objcgs = page_objcgs(page); + objcgs = page_objcgs_check(page); if (!objcgs) continue;