mm: memcontrol: rename memcg_kmem_enabled()

Currently there are two kmem-related helper functions with a confusing
semantics: memcg_kmem_enabled() and mem_cgroup_kmem_disabled().

The problem is that an obvious expectation
memcg_kmem_enabled() == !mem_cgroup_kmem_disabled(),
can be false.

mem_cgroup_kmem_disabled() is similar to mem_cgroup_disabled(): it returns
true only if CONFIG_MEMCG_KMEM is not set or the kmem accounting is
disabled using a boot time kernel option "cgroup.memory=nokmem".  It never
changes the value dynamically.

memcg_kmem_enabled() is different: it always returns false until the first
non-root memory cgroup will get online (assuming the kernel memory
accounting is enabled).  It's goal is to improve the performance on
systems without the cgroupfs mounted/memory controller enabled or on the
systems with only the root memory cgroup.

To make things more obvious and avoid potential bugs, let's rename
memcg_kmem_enabled() to memcg_kmem_online().

Link: https://lkml.kernel.org/r/20230213192922.1146370-1-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 3547869..5567319 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1776,24 +1776,24 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page);
 int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size);
 void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size);
 
-extern struct static_key_false memcg_kmem_enabled_key;
+extern struct static_key_false memcg_kmem_online_key;
 
-static inline bool memcg_kmem_enabled(void)
+static inline bool memcg_kmem_online(void)
 {
-       return static_branch_likely(&memcg_kmem_enabled_key);
+       return static_branch_likely(&memcg_kmem_online_key);
 }
 
 static inline int memcg_kmem_charge_page(struct page *page, gfp_t gfp,
                                         int order)
 {
-       if (memcg_kmem_enabled())
+       if (memcg_kmem_online())
                return __memcg_kmem_charge_page(page, gfp, order);
        return 0;
 }
 
 static inline void memcg_kmem_uncharge_page(struct page *page, int order)
 {
-       if (memcg_kmem_enabled())
+       if (memcg_kmem_online())
                __memcg_kmem_uncharge_page(page, order);
 }
 
@@ -1814,7 +1814,7 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 {
        struct mem_cgroup *memcg;
 
-       if (!memcg_kmem_enabled())
+       if (!memcg_kmem_online())
                return;
 
        rcu_read_lock();
@@ -1854,7 +1854,7 @@ static inline struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
        return NULL;
 }
 
-static inline bool memcg_kmem_enabled(void)
+static inline bool memcg_kmem_online(void)
 {
        return false;
 }

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1733545..3e3cdb9 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -345,8 +345,8 @@ static void memcg_reparent_objcgs(struct mem_cgroup *memcg,
  * conditional to this static branch, we'll have to allow modules that does
  * kmem_cache_alloc and the such to see this symbol as well
  */
-DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
-EXPORT_SYMBOL(memcg_kmem_enabled_key);
+DEFINE_STATIC_KEY_FALSE(memcg_kmem_online_key);
+EXPORT_SYMBOL(memcg_kmem_online_key);
 #endif
 
 /**
@@ -3034,7 +3034,7 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
 {
        struct obj_cgroup *objcg;
 
-       if (!memcg_kmem_enabled())
+       if (!memcg_kmem_online())
                return NULL;
 
        if (PageMemcgKmem(page)) {
@@ -3746,7 +3746,7 @@ static int memcg_online_kmem(struct mem_cgroup *memcg)
        objcg->memcg = memcg;
        rcu_assign_pointer(memcg->objcg, objcg);
 
-       static_branch_enable(&memcg_kmem_enabled_key);
+       static_branch_enable(&memcg_kmem_online_key);
 
        memcg->kmemcg_id = memcg->id.id;
 

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4b6bcec..4c9ab8b 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1410,7 +1410,7 @@ 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() && PageMemcgKmem(page))
+               if (memcg_kmem_online() && PageMemcgKmem(page))
                        __memcg_kmem_uncharge_page(page, order);
                reset_page_owner(page, order);
                page_table_check_free(page, order);
@@ -1441,7 +1441,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
        }
        if (PageMappingFlags(page))
                page->mapping = NULL;
-       if (memcg_kmem_enabled() && PageMemcgKmem(page))
+       if (memcg_kmem_online() && PageMemcgKmem(page))
                __memcg_kmem_uncharge_page(page, order);
        if (check_free && free_page_is_bad(page))
                bad++;
@@ -5432,7 +5432,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
                goto out;
 
        /* Bulk allocator does not support memcg accounting. */
-       if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT))
+       if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT))
                goto failed;
 
        /* Use the single page allocator for one page. */
@@ -5604,7 +5604,7 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
        page = __alloc_pages_slowpath(alloc_gfp, order, &ac);
 
 out:
-       if (memcg_kmem_enabled() && (gfp & __GFP_ACCOUNT) && page &&
+       if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT) && page &&
            unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) {
                __free_pages(page, order);
                page = NULL;

diff --git a/mm/percpu.c b/mm/percpu.c
index acd78da..28e07ed 100644 (file)
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1625,7 +1625,7 @@ static bool pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
 {
        struct obj_cgroup *objcg;
 
-       if (!memcg_kmem_enabled() || !(gfp & __GFP_ACCOUNT))
+       if (!memcg_kmem_online() || !(gfp & __GFP_ACCOUNT))
                return true;
 
        objcg = get_obj_cgroup_from_current();

diff --git a/mm/slab.h b/mm/slab.h
index 63fb4c0..43966aa 100644 (file)
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -494,7 +494,7 @@ static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s,
 {
        struct obj_cgroup *objcg;
 
-       if (!memcg_kmem_enabled())
+       if (!memcg_kmem_online())
                return true;
 
        if (!(flags & __GFP_ACCOUNT) && !(s->flags & SLAB_ACCOUNT))
@@ -535,7 +535,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
        unsigned long off;
        size_t i;
 
-       if (!memcg_kmem_enabled() || !objcg)
+       if (!memcg_kmem_online() || !objcg)
                return;
 
        for (i = 0; i < size; i++) {
@@ -567,7 +567,7 @@ static inline void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
        struct obj_cgroup **objcgs;
        int i;
 
-       if (!memcg_kmem_enabled())
+       if (!memcg_kmem_online())
                return;
 
        objcgs = slab_objcgs(slab);
@@ -649,7 +649,7 @@ static inline struct kmem_cache *virt_to_cache(const void *obj)
 static __always_inline void account_slab(struct slab *slab, int order,
                                         struct kmem_cache *s, gfp_t gfp)
 {
-       if (memcg_kmem_enabled() && (s->flags & SLAB_ACCOUNT))
+       if (memcg_kmem_online() && (s->flags & SLAB_ACCOUNT))
                memcg_alloc_slab_cgroups(slab, s, gfp, true);
 
        mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),
@@ -659,7 +659,7 @@ static __always_inline void account_slab(struct slab *slab, int order,
 static __always_inline void unaccount_slab(struct slab *slab, int order,
                                           struct kmem_cache *s)
 {
-       if (memcg_kmem_enabled())
+       if (memcg_kmem_online())
                memcg_free_slab_cgroups(slab);
 
        mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 34535bb..098c791 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -915,7 +915,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
                }
 
                /* Call non-slab shrinkers even though kmem is disabled */
-               if (!memcg_kmem_enabled() &&
+               if (!memcg_kmem_online() &&
                    !(shrinker->flags & SHRINKER_NONSLAB))
                        continue;