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    Subject[PATCH v3 08/19] mm: memcg/slab: save obj_cgroup for non-root slab objects
    Date
    Store the obj_cgroup pointer in the corresponding place of
    page->obj_cgroups for each allocated non-root slab object.
    Make sure that each allocated object holds a reference to obj_cgroup.

    Objcg pointer is obtained from the memcg->objcg dereferencing
    in memcg_kmem_get_cache() and passed from pre_alloc_hook to
    post_alloc_hook. Then in case of successful allocation(s) it's
    getting stored in the page->obj_cgroups vector.

    The objcg obtaining part look a bit bulky now, but it will be simplified
    by next commits in the series.

    Signed-off-by: Roman Gushchin <guro@fb.com>
    ---
    include/linux/memcontrol.h | 3 +-
    mm/memcontrol.c | 14 +++++++--
    mm/slab.c | 18 +++++++-----
    mm/slab.h | 60 ++++++++++++++++++++++++++++++++++----
    mm/slub.c | 14 +++++----
    5 files changed, 88 insertions(+), 21 deletions(-)

    diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
    index bf1be842fd27..44b7d1244620 100644
    --- a/include/linux/memcontrol.h
    +++ b/include/linux/memcontrol.h
    @@ -1426,7 +1426,8 @@ static inline void memcg_set_shrinker_bit(struct mem_cgroup *memcg,
    }
    #endif

    -struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
    +struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
    + struct obj_cgroup **objcgp);
    void memcg_kmem_put_cache(struct kmem_cache *cachep);

    #ifdef CONFIG_MEMCG_KMEM
    diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    index 63826e460b3f..deb6ceae7577 100644
    --- a/mm/memcontrol.c
    +++ b/mm/memcontrol.c
    @@ -2964,7 +2964,8 @@ static inline bool memcg_kmem_bypass(void)
    * done with it, memcg_kmem_put_cache() must be called to release the
    * reference.
    */
    -struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
    +struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep,
    + struct obj_cgroup **objcgp)
    {
    struct mem_cgroup *memcg;
    struct kmem_cache *memcg_cachep;
    @@ -3020,8 +3021,17 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
    */
    if (unlikely(!memcg_cachep))
    memcg_schedule_kmem_cache_create(memcg, cachep);
    - else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt))
    + else if (percpu_ref_tryget(&memcg_cachep->memcg_params.refcnt)) {
    + struct obj_cgroup *objcg = rcu_dereference(memcg->objcg);
    +
    + if (!objcg || !obj_cgroup_tryget(objcg)) {
    + percpu_ref_put(&memcg_cachep->memcg_params.refcnt);
    + goto out_unlock;
    + }
    +
    + *objcgp = objcg;
    cachep = memcg_cachep;
    + }
    out_unlock:
    rcu_read_unlock();
    return cachep;
    diff --git a/mm/slab.c b/mm/slab.c
    index f2d67984595b..ad38fbae4042 100644
    --- a/mm/slab.c
    +++ b/mm/slab.c
    @@ -3223,9 +3223,10 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
    unsigned long save_flags;
    void *ptr;
    int slab_node = numa_mem_id();
    + struct obj_cgroup *objcg = NULL;

    flags &= gfp_allowed_mask;
    - cachep = slab_pre_alloc_hook(cachep, flags);
    + cachep = slab_pre_alloc_hook(cachep, &objcg, 1, flags);
    if (unlikely(!cachep))
    return NULL;

    @@ -3261,7 +3262,7 @@ slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
    if (unlikely(slab_want_init_on_alloc(flags, cachep)) && ptr)
    memset(ptr, 0, cachep->object_size);

    - slab_post_alloc_hook(cachep, flags, 1, &ptr);
    + slab_post_alloc_hook(cachep, objcg, flags, 1, &ptr);
    return ptr;
    }

    @@ -3302,9 +3303,10 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
    {
    unsigned long save_flags;
    void *objp;
    + struct obj_cgroup *objcg = NULL;

    flags &= gfp_allowed_mask;
    - cachep = slab_pre_alloc_hook(cachep, flags);
    + cachep = slab_pre_alloc_hook(cachep, &objcg, 1, flags);
    if (unlikely(!cachep))
    return NULL;

    @@ -3318,7 +3320,7 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
    if (unlikely(slab_want_init_on_alloc(flags, cachep)) && objp)
    memset(objp, 0, cachep->object_size);

    - slab_post_alloc_hook(cachep, flags, 1, &objp);
    + slab_post_alloc_hook(cachep, objcg, flags, 1, &objp);
    return objp;
    }

    @@ -3440,6 +3442,7 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
    memset(objp, 0, cachep->object_size);
    kmemleak_free_recursive(objp, cachep->flags);
    objp = cache_free_debugcheck(cachep, objp, caller);
    + memcg_slab_free_hook(cachep, virt_to_head_page(objp), objp);

    /*
    * Skip calling cache_free_alien() when the platform is not numa.
    @@ -3505,8 +3508,9 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
    void **p)
    {
    size_t i;
    + struct obj_cgroup *objcg = NULL;

    - s = slab_pre_alloc_hook(s, flags);
    + s = slab_pre_alloc_hook(s, &objcg, size, flags);
    if (!s)
    return 0;

    @@ -3529,13 +3533,13 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
    for (i = 0; i < size; i++)
    memset(p[i], 0, s->object_size);

    - slab_post_alloc_hook(s, flags, size, p);
    + slab_post_alloc_hook(s, objcg, flags, size, p);
    /* FIXME: Trace call missing. Christoph would like a bulk variant */
    return size;
    error:
    local_irq_enable();
    cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_);
    - slab_post_alloc_hook(s, flags, i, p);
    + slab_post_alloc_hook(s, objcg, flags, i, p);
    __kmem_cache_free_bulk(s, i, p);
    return 0;
    }
    diff --git a/mm/slab.h b/mm/slab.h
    index 44def57f050e..525e09e05743 100644
    --- a/mm/slab.h
    +++ b/mm/slab.h
    @@ -437,6 +437,41 @@ static inline void memcg_free_page_obj_cgroups(struct page *page)
    page->obj_cgroups = NULL;
    }

    +static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
    + struct obj_cgroup *objcg,
    + size_t size, void **p)
    +{
    + struct page *page;
    + unsigned long off;
    + size_t i;
    +
    + for (i = 0; i < size; i++) {
    + if (likely(p[i])) {
    + page = virt_to_head_page(p[i]);
    + off = obj_to_index(s, page, p[i]);
    + obj_cgroup_get(objcg);
    + page_obj_cgroups(page)[off] = objcg;
    + }
    + }
    + obj_cgroup_put(objcg);
    + memcg_kmem_put_cache(s);
    +}
    +
    +static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
    + void *p)
    +{
    + struct obj_cgroup *objcg;
    + unsigned int off;
    +
    + if (!memcg_kmem_enabled() || is_root_cache(s))
    + return;
    +
    + off = obj_to_index(s, page, p);
    + objcg = page_obj_cgroups(page)[off];
    + page_obj_cgroups(page)[off] = NULL;
    + obj_cgroup_put(objcg);
    +}
    +
    extern void slab_init_memcg_params(struct kmem_cache *);
    extern void memcg_link_cache(struct kmem_cache *s, struct mem_cgroup *memcg);

    @@ -496,6 +531,17 @@ static inline void memcg_free_page_obj_cgroups(struct page *page)
    {
    }

    +static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
    + struct obj_cgroup *objcg,
    + size_t size, void **p)
    +{
    +}
    +
    +static inline void memcg_slab_free_hook(struct kmem_cache *s, struct page *page,
    + void *p)
    +{
    +}
    +
    static inline void slab_init_memcg_params(struct kmem_cache *s)
    {
    }
    @@ -604,7 +650,8 @@ static inline size_t slab_ksize(const struct kmem_cache *s)
    }

    static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
    - gfp_t flags)
    + struct obj_cgroup **objcgp,
    + size_t size, gfp_t flags)
    {
    flags &= gfp_allowed_mask;

    @@ -618,13 +665,14 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,

    if (memcg_kmem_enabled() &&
    ((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT)))
    - return memcg_kmem_get_cache(s);
    + return memcg_kmem_get_cache(s, objcgp);

    return s;
    }

    -static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
    - size_t size, void **p)
    +static inline void slab_post_alloc_hook(struct kmem_cache *s,
    + struct obj_cgroup *objcg,
    + gfp_t flags, size_t size, void **p)
    {
    size_t i;

    @@ -636,8 +684,8 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
    s->flags, flags);
    }

    - if (memcg_kmem_enabled())
    - memcg_kmem_put_cache(s);
    + if (!is_root_cache(s))
    + memcg_slab_post_alloc_hook(s, objcg, size, p);
    }

    #ifndef CONFIG_SLOB
    diff --git a/mm/slub.c b/mm/slub.c
    index 68c2c45dfac1..67ae40fcfcda 100644
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -2734,8 +2734,9 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
    struct kmem_cache_cpu *c;
    struct page *page;
    unsigned long tid;
    + struct obj_cgroup *objcg = NULL;

    - s = slab_pre_alloc_hook(s, gfpflags);
    + s = slab_pre_alloc_hook(s, &objcg, 1, gfpflags);
    if (!s)
    return NULL;
    redo:
    @@ -2811,7 +2812,7 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
    if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object)
    memset(object, 0, s->object_size);

    - slab_post_alloc_hook(s, gfpflags, 1, &object);
    + slab_post_alloc_hook(s, objcg, gfpflags, 1, &object);

    return object;
    }
    @@ -3016,6 +3017,8 @@ static __always_inline void do_slab_free(struct kmem_cache *s,
    void *tail_obj = tail ? : head;
    struct kmem_cache_cpu *c;
    unsigned long tid;
    +
    + memcg_slab_free_hook(s, page, head);
    redo:
    /*
    * Determine the currently cpus per cpu slab.
    @@ -3195,9 +3198,10 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
    {
    struct kmem_cache_cpu *c;
    int i;
    + struct obj_cgroup *objcg = NULL;

    /* memcg and kmem_cache debug support */
    - s = slab_pre_alloc_hook(s, flags);
    + s = slab_pre_alloc_hook(s, &objcg, size, flags);
    if (unlikely(!s))
    return false;
    /*
    @@ -3251,11 +3255,11 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
    }

    /* memcg and kmem_cache debug support */
    - slab_post_alloc_hook(s, flags, size, p);
    + slab_post_alloc_hook(s, objcg, flags, size, p);
    return i;
    error:
    local_irq_enable();
    - slab_post_alloc_hook(s, flags, i, p);
    + slab_post_alloc_hook(s, objcg, flags, i, p);
    __kmem_cache_free_bulk(s, i, p);
    return 0;
    }
    --
    2.25.3
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