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authorRoman Gushchin <roman.gushchin@linux.dev>2023-10-20 01:53:44 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-10-26 02:47:11 +0300
commite86828e5446d95676835679837d995dec188d2be (patch)
treed74a46f7cf5209fe29e3337b3b280e3c728932b7 /mm/slab.h
parent675d6c9b59e313ca2573c93e8fd87011a99bb8ce (diff)
downloadlinux-e86828e5446d95676835679837d995dec188d2be.tar.xz
mm: kmem: scoped objcg protection
Switch to a scope-based protection of the objcg pointer on slab/kmem allocation paths. Instead of using the get_() semantics in the pre-allocation hook and put the reference afterwards, let's rely on the fact that objcg is pinned by the scope. It's possible because: 1) if the objcg is received from the current task struct, the task is keeping a reference to the objcg. 2) if the objcg is received from an active memcg (remote charging), the memcg is pinned by the scope and has a reference to the corresponding objcg. Link: https://lkml.kernel.org/r/20231019225346.1822282-5-roman.gushchin@linux.dev Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev> Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org> Acked-by: Shakeel Butt <shakeelb@google.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: David Rientjes <rientjes@google.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/slab.h')
-rw-r--r--mm/slab.h15
1 files changed, 8 insertions, 7 deletions
diff --git a/mm/slab.h b/mm/slab.h
index 799a315695c6..3d07fb428393 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -484,7 +484,12 @@ static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s,
if (!(flags & __GFP_ACCOUNT) && !(s->flags & SLAB_ACCOUNT))
return true;
- objcg = get_obj_cgroup_from_current();
+ /*
+ * The obtained objcg pointer is safe to use within the current scope,
+ * defined by current task or set_active_memcg() pair.
+ * obj_cgroup_get() is used to get a permanent reference.
+ */
+ objcg = current_obj_cgroup();
if (!objcg)
return true;
@@ -497,17 +502,14 @@ static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s,
css_put(&memcg->css);
if (ret)
- goto out;
+ return false;
}
if (obj_cgroup_charge(objcg, flags, objects * obj_full_size(s)))
- goto out;
+ return false;
*objcgp = objcg;
return true;
-out:
- obj_cgroup_put(objcg);
- return false;
}
static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
@@ -542,7 +544,6 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
obj_cgroup_uncharge(objcg, obj_full_size(s));
}
}
- obj_cgroup_put(objcg);
}
static inline void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,