From bcfe06bf2622f7c4899468e427683aec49070687 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Tue, 1 Dec 2020 13:58:27 -0800 Subject: mm: memcontrol: Use helpers to read page's memcg data 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 Signed-off-by: Andrew Morton Signed-off-by: Alexei Starovoitov Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko 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 --- mm/debug.c | 4 +- mm/huge_memory.c | 4 +- mm/memcontrol.c | 121 +++++++++++++++++++++++++------------------------------ mm/page_alloc.c | 4 +- mm/page_io.c | 6 ++- mm/slab.h | 9 ++--- mm/workingset.c | 2 +- 7 files changed, 71 insertions(+), 79 deletions(-) (limited to 'mm') 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 @@ hex_only: 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 9474dbc150ed..cedfb3503411 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -470,7 +470,7 @@ 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) @@ -2765,7 +2765,7 @@ 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 3dcbf24d2227..3968d68503cb 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); @@ -1050,7 +1041,7 @@ 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; @@ -1349,7 +1340,7 @@ 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. @@ -2109,7 +2100,7 @@ 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 @@ -2141,7 +2132,7 @@ 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; @@ -2149,7 +2140,7 @@ again: 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; } @@ -2187,14 +2178,14 @@ 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); @@ -2884,7 +2875,7 @@ 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: * @@ -2893,7 +2884,7 @@ 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 @@ -2908,8 +2899,7 @@ 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); @@ -2920,6 +2910,12 @@ 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. */ @@ -2932,17 +2928,6 @@ 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 @@ -2960,8 +2945,14 @@ 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) @@ -3099,7 +3090,7 @@ 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; } @@ -3115,7 +3106,7 @@ 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) @@ -3123,7 +3114,7 @@ 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 */ @@ -3274,7 +3265,7 @@ void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size) */ void mem_cgroup_split_huge_fixup(struct page *head) { - struct mem_cgroup *memcg = head->mem_cgroup; + struct mem_cgroup *memcg = page_memcg(head); int i; if (mem_cgroup_disabled()) @@ -3282,7 +3273,7 @@ void mem_cgroup_split_huge_fixup(struct page *head) for (i = 1; i < HPAGE_PMD_NR; i++) { css_get(&memcg->css); - head[i].mem_cgroup = memcg; + head[i].memcg_data = (unsigned long)memcg; } } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ @@ -4664,7 +4655,7 @@ 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; @@ -5641,14 +5632,14 @@ 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); @@ -5703,13 +5694,13 @@ 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. */ @@ -5718,7 +5709,7 @@ 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); @@ -5784,7 +5775,7 @@ 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; @@ -5828,7 +5819,7 @@ 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); @@ -6774,12 +6765,12 @@ 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); @@ -6863,21 +6854,21 @@ 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); @@ -6894,7 +6885,7 @@ 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); } @@ -6937,7 +6928,7 @@ 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); @@ -6987,11 +6978,11 @@ 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; @@ -7186,7 +7177,7 @@ 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) @@ -7207,7 +7198,7 @@ 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); @@ -7250,7 +7241,7 @@ 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) @@ -7331,7 +7322,7 @@ 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 23f5066bd4a5..271133b8243b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1092,7 +1092,7 @@ 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; @@ -1117,7 +1117,7 @@ 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 433df1263349..9bca17ecc4df 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -291,12 +291,14 @@ 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 6d7c6a5056ba..e2535cee0d33 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -242,18 +242,17 @@ 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, @@ -262,7 +261,7 @@ 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); -- cgit v1.2.3 From 270c6a71460e12b07b1dcadf7457ff95b6c6e8f4 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Tue, 1 Dec 2020 13:58:28 -0800 Subject: mm: memcontrol/slab: Use helpers to access slab page's memcg_data To gather all direct accesses to struct page's memcg_data field in one place, let's introduce 3 new helpers to use in the slab accounting code: struct obj_cgroup **page_objcgs(struct page *page); struct obj_cgroup **page_objcgs_check(struct page *page); bool set_page_objcgs(struct page *page, struct obj_cgroup **objcgs); They are similar to the corresponding API for generic pages, except that the setter can return false, indicating that the value has been already set from a different thread. Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Alexei Starovoitov Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/20201027001657.3398190-3-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-3-guro@fb.com --- include/linux/memcontrol.h | 64 ++++++++++++++++++++++++++++++++++++++++++++++ mm/memcontrol.c | 6 ++--- mm/slab.h | 35 ++++++------------------- 3 files changed, 75 insertions(+), 30 deletions(-) (limited to 'mm') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index f95c1433461c..c7ac0a5b8989 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -416,6 +416,70 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) return (struct mem_cgroup *)memcg_data; } +#ifdef CONFIG_MEMCG_KMEM +/* + * page_objcgs - get the object cgroups vector associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the object cgroups vector associated with the page, + * or NULL. This function assumes that the page is known to have an + * associated object cgroups vector. It's not safe to call this function + * against pages, which might have an associated memory cgroup: e.g. + * kernel stack pages. + */ +static inline struct obj_cgroup **page_objcgs(struct page *page) +{ + return (struct obj_cgroup **)(READ_ONCE(page->memcg_data) & ~0x1UL); +} + +/* + * page_objcgs_check - get the object cgroups vector associated with a page + * @page: a pointer to the page struct + * + * Returns a pointer to the object cgroups vector associated with the page, + * or NULL. This function is safe to use if the page can be directly associated + * with a memory cgroup. + */ +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); + + return NULL; +} + +/* + * set_page_objcgs - associate a page with a object cgroups vector + * @page: a pointer to the page struct + * @objcgs: a pointer to the object cgroups vector + * + * Atomically associates a page with a vector of object cgroups. + */ +static inline bool set_page_objcgs(struct page *page, + struct obj_cgroup **objcgs) +{ + return !cmpxchg(&page->memcg_data, 0, (unsigned long)objcgs | 0x1UL); +} +#else +static inline struct obj_cgroup **page_objcgs(struct page *page) +{ + return NULL; +} + +static inline struct obj_cgroup **page_objcgs_check(struct page *page) +{ + return NULL; +} + +static inline bool set_page_objcgs(struct page *page, + struct obj_cgroup **objcgs) +{ + return true; +} +#endif + static __always_inline bool memcg_stat_item_in_bytes(int idx) { if (idx == MEMCG_PERCPU_B) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3968d68503cb..0054b4846770 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2899,7 +2899,7 @@ int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, if (!vec) return -ENOMEM; - if (cmpxchg(&page->memcg_data, 0, (unsigned long)vec | 0x1UL)) + if (!set_page_objcgs(page, vec)) kfree(vec); else kmemleak_not_leak(vec); @@ -2933,12 +2933,12 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p) * Memcg membership data for each individual object is saved in * the page->obj_cgroups. */ - if (page_has_obj_cgroups(page)) { + if (page_objcgs_check(page)) { struct obj_cgroup *objcg; unsigned int off; off = obj_to_index(page->slab_cache, page, p); - objcg = page_obj_cgroups(page)[off]; + objcg = page_objcgs(page)[off]; if (objcg) return obj_cgroup_memcg(objcg); diff --git a/mm/slab.h b/mm/slab.h index e2535cee0d33..9a54a0cb5cca 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -239,28 +239,12 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla } #ifdef CONFIG_MEMCG_KMEM -static inline struct obj_cgroup **page_obj_cgroups(struct page *page) -{ - /* - * 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 **)(page->memcg_data & ~0x1UL); -} - -static inline bool page_has_obj_cgroups(struct page *page) -{ - return page->memcg_data & 0x1UL; -} - int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s, gfp_t gfp); static inline void memcg_free_page_obj_cgroups(struct page *page) { - kfree(page_obj_cgroups(page)); + kfree(page_objcgs(page)); page->memcg_data = 0; } @@ -322,7 +306,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s, if (likely(p[i])) { page = virt_to_head_page(p[i]); - if (!page_has_obj_cgroups(page) && + if (!page_objcgs(page) && memcg_alloc_page_obj_cgroups(page, s, flags)) { obj_cgroup_uncharge(objcg, obj_full_size(s)); continue; @@ -330,7 +314,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s, off = obj_to_index(s, page, p[i]); obj_cgroup_get(objcg); - page_obj_cgroups(page)[off] = objcg; + page_objcgs(page)[off] = objcg; mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s), obj_full_size(s)); } else { @@ -344,6 +328,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, void **p, int objects) { struct kmem_cache *s; + struct obj_cgroup **objcgs; struct obj_cgroup *objcg; struct page *page; unsigned int off; @@ -357,7 +342,8 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, continue; page = virt_to_head_page(p[i]); - if (!page_has_obj_cgroups(page)) + objcgs = page_objcgs(page); + if (!objcgs) continue; if (!s_orig) @@ -366,11 +352,11 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, s = s_orig; off = obj_to_index(s, page, p[i]); - objcg = page_obj_cgroups(page)[off]; + objcg = objcgs[off]; if (!objcg) continue; - page_obj_cgroups(page)[off] = NULL; + objcgs[off] = NULL; obj_cgroup_uncharge(objcg, obj_full_size(s)); mod_objcg_state(objcg, page_pgdat(page), cache_vmstat_idx(s), -obj_full_size(s)); @@ -379,11 +365,6 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s_orig, } #else /* CONFIG_MEMCG_KMEM */ -static inline bool page_has_obj_cgroups(struct page *page) -{ - return false; -} - static inline struct mem_cgroup *memcg_from_slab_obj(void *ptr) { return NULL; -- cgit v1.2.3 From 18b2db3b0385226b71cb3288474fa5a6e4a45474 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Tue, 1 Dec 2020 13:58:30 -0800 Subject: mm: Convert page kmemcg type to a page memcg flag PageKmemcg flag is currently defined as a page type (like buddy, offline, table and guard). Semantically it means that the page was accounted as a kernel memory by the page allocator and has to be uncharged on the release. As a side effect of defining the flag as a page type, the accounted page can't be mapped to userspace (look at page_has_type() and comments above). In particular, this blocks the accounting of vmalloc-backed memory used by some bpf maps, because these maps do map the memory to userspace. One option is to fix it by complicating the access to page->mapcount, which provides some free bits for page->page_type. But it's way better to move this flag into page->memcg_data flags. Indeed, the flag makes no sense without enabled memory cgroups and memory cgroup pointer set in particular. This commit replaces PageKmemcg() and __SetPageKmemcg() with PageMemcgKmem() and an open-coded OR operation setting the memcg pointer with the MEMCG_DATA_KMEM bit. __ClearPageKmemcg() can be simple deleted, as the whole memcg_data is zeroed at once. As a bonus, on !CONFIG_MEMCG build the PageMemcgKmem() check will be compiled out. Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Alexei Starovoitov Reviewed-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko Link: https://lkml.kernel.org/r/20201027001657.3398190-5-guro@fb.com Link: https://lore.kernel.org/bpf/20201201215900.3569844-5-guro@fb.com --- include/linux/memcontrol.h | 37 +++++++++++++++++++++++++++++++++---- include/linux/page-flags.h | 11 ++--------- mm/memcontrol.c | 16 +++++----------- mm/page_alloc.c | 4 ++-- 4 files changed, 42 insertions(+), 26 deletions(-) (limited to 'mm') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 99a4841d658b..7c9d43476166 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -346,8 +346,10 @@ 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), + /* page has been accounted as a non-slab kernel page */ + MEMCG_DATA_KMEM = (1UL << 1), /* the next bit after the last actual flag */ - __NR_MEMCG_DATA_FLAGS = (1UL << 1), + __NR_MEMCG_DATA_FLAGS = (1UL << 2), }; #define MEMCG_DATA_FLAGS_MASK (__NR_MEMCG_DATA_FLAGS - 1) @@ -369,8 +371,12 @@ enum page_memcg_data_flags { */ static inline struct mem_cgroup *page_memcg(struct page *page) { + unsigned long memcg_data = page->memcg_data; + VM_BUG_ON_PAGE(PageSlab(page), page); - return (struct mem_cgroup *)page->memcg_data; + VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_OBJCGS, page); + + return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } /* @@ -387,7 +393,8 @@ 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); + return (struct mem_cgroup *)(READ_ONCE(page->memcg_data) & + ~MEMCG_DATA_FLAGS_MASK); } /* @@ -416,7 +423,21 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) if (memcg_data & MEMCG_DATA_OBJCGS) return NULL; - return (struct mem_cgroup *)memcg_data; + return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); +} + +/* + * PageMemcgKmem - check if the page has MemcgKmem flag set + * @page: a pointer to the page struct + * + * Checks if the page has MemcgKmem flag set. The caller must ensure that + * the page has an associated memory cgroup. It's not safe to call this function + * against some types of pages, e.g. slab pages. + */ +static inline bool PageMemcgKmem(struct page *page) +{ + VM_BUG_ON_PAGE(page->memcg_data & MEMCG_DATA_OBJCGS, page); + return page->memcg_data & MEMCG_DATA_KMEM; } #ifdef CONFIG_MEMCG_KMEM @@ -435,6 +456,7 @@ static inline struct obj_cgroup **page_objcgs(struct page *page) unsigned long memcg_data = READ_ONCE(page->memcg_data); VM_BUG_ON_PAGE(memcg_data && !(memcg_data & MEMCG_DATA_OBJCGS), page); + VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_KMEM, page); return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } @@ -454,6 +476,8 @@ static inline struct obj_cgroup **page_objcgs_check(struct page *page) if (!memcg_data || !(memcg_data & MEMCG_DATA_OBJCGS)) return NULL; + VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_KMEM, page); + return (struct obj_cgroup **)(memcg_data & ~MEMCG_DATA_FLAGS_MASK); } @@ -1109,6 +1133,11 @@ static inline struct mem_cgroup *page_memcg_check(struct page *page) return NULL; } +static inline bool PageMemcgKmem(struct page *page) +{ + return false; +} + static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg) { return true; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 4f6ba9379112..fc0e1bd48e73 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -715,9 +715,8 @@ PAGEFLAG_FALSE(DoubleMap) #define PAGE_MAPCOUNT_RESERVE -128 #define PG_buddy 0x00000080 #define PG_offline 0x00000100 -#define PG_kmemcg 0x00000200 -#define PG_table 0x00000400 -#define PG_guard 0x00000800 +#define PG_table 0x00000200 +#define PG_guard 0x00000400 #define PageType(page, flag) \ ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) @@ -768,12 +767,6 @@ PAGE_TYPE_OPS(Buddy, buddy) */ PAGE_TYPE_OPS(Offline, offline) -/* - * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on - * pages allocated with __GFP_ACCOUNT. It gets cleared on page free. - */ -PAGE_TYPE_OPS(Kmemcg, kmemcg) - /* * Marks pages in use as page tables. */ diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0054b4846770..e0366e306221 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3090,8 +3090,8 @@ 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->memcg_data = (unsigned long)memcg; - __SetPageKmemcg(page); + page->memcg_data = (unsigned long)memcg | + MEMCG_DATA_KMEM; return 0; } css_put(&memcg->css); @@ -3116,10 +3116,6 @@ void __memcg_kmem_uncharge_page(struct page *page, int order) __memcg_kmem_uncharge(memcg, nr_pages); page->memcg_data = 0; css_put(&memcg->css); - - /* slab pages do not have PageKmemcg flag set */ - if (PageKmemcg(page)) - __ClearPageKmemcg(page); } static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes) @@ -6877,12 +6873,10 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug) nr_pages = compound_nr(page); ug->nr_pages += nr_pages; - if (!PageKmemcg(page)) { - ug->pgpgout++; - } else { + if (PageMemcgKmem(page)) ug->nr_kmem += nr_pages; - __ClearPageKmemcg(page); - } + else + ug->pgpgout++; ug->dummy_page = page; page->memcg_data = 0; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 271133b8243b..3c53018c9c61 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1214,7 +1214,7 @@ static __always_inline bool free_pages_prepare(struct page *page, * Do not let hwpoison pages hit pcplists/buddy * Untie memcg state and reset page's owner */ - if (memcg_kmem_enabled() && PageKmemcg(page)) + if (memcg_kmem_enabled() && PageMemcgKmem(page)) __memcg_kmem_uncharge_page(page, order); reset_page_owner(page, order); return false; @@ -1244,7 +1244,7 @@ static __always_inline bool free_pages_prepare(struct page *page, } if (PageMappingFlags(page)) page->mapping = NULL; - if (memcg_kmem_enabled() && PageKmemcg(page)) + if (memcg_kmem_enabled() && PageMemcgKmem(page)) __memcg_kmem_uncharge_page(page, order); if (check_free) bad += check_free_page(page); -- cgit v1.2.3