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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/memcontrol.c
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/memcontrol.c')
-rw-r--r--mm/memcontrol.c47
1 files changed, 45 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ff036d5d339d..a6457c8b5e16 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3170,6 +3170,49 @@ from_memcg:
return objcg;
}
+__always_inline struct obj_cgroup *current_obj_cgroup(void)
+{
+ struct mem_cgroup *memcg;
+ struct obj_cgroup *objcg;
+
+ if (in_task()) {
+ memcg = current->active_memcg;
+ if (unlikely(memcg))
+ goto from_memcg;
+
+ objcg = READ_ONCE(current->objcg);
+ if (unlikely((unsigned long)objcg & CURRENT_OBJCG_UPDATE_FLAG))
+ objcg = current_objcg_update();
+ /*
+ * Objcg reference is kept by the task, so it's safe
+ * to use the objcg by the current task.
+ */
+ return objcg;
+ }
+
+ memcg = this_cpu_read(int_active_memcg);
+ if (unlikely(memcg))
+ goto from_memcg;
+
+ return NULL;
+
+from_memcg:
+ for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
+ /*
+ * Memcg pointer is protected by scope (see set_active_memcg())
+ * and is pinning the corresponding objcg, so objcg can't go
+ * away and can be used within the scope without any additional
+ * protection.
+ */
+ objcg = rcu_dereference_check(memcg->objcg, 1);
+ if (likely(objcg))
+ break;
+ objcg = NULL;
+ }
+
+ return objcg;
+}
+
struct obj_cgroup *get_obj_cgroup_from_folio(struct folio *folio)
{
struct obj_cgroup *objcg;
@@ -3264,15 +3307,15 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
struct obj_cgroup *objcg;
int ret = 0;
- objcg = get_obj_cgroup_from_current();
+ objcg = current_obj_cgroup();
if (objcg) {
ret = obj_cgroup_charge_pages(objcg, gfp, 1 << order);
if (!ret) {
+ obj_cgroup_get(objcg);
page->memcg_data = (unsigned long)objcg |
MEMCG_DATA_KMEM;
return 0;
}
- obj_cgroup_put(objcg);
}
return ret;
}