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Miller" , Jakub Kicinski , Paolo Abeni References: <46c1c59e-1368-620d-e57a-f35c2c82084d@linux.dev> <55605876-d05a-8be3-a6ae-ec26de9ee178@openvz.org> From: Vasily Averin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/21/22 18:56, Shakeel Butt wrote: > On Sat, Apr 16, 2022 at 11:39 PM Vasily Averin wrote: >> @@ -1147,7 +1148,13 @@ static int __register_pernet_operations(struct list_head *list, >> * setup_net() and cleanup_net() are not possible. >> */ >> for_each_net(net) { >> + struct mem_cgroup *old, *memcg = NULL; >> +#ifdef CONFIG_MEMCG >> + memcg = (net == &init_net) ? root_mem_cgroup : mem_cgroup_from_obj(net); > > memcg from obj is unstable, so you need a reference on memcg. You can > introduce get_mem_cgroup_from_kmem() which works for both > MEMCG_DATA_OBJCGS and MEMCG_DATA_KMEM. For uncharged objects (like > init_net) it should return NULL. Could you please elaborate with more details? It seems to me mem_cgroup_from_obj() does everything exactly as you say: - for slab objects it returns memcg taken from according slab->memcg_data - for ex-slab objects (i.e. page->memcg_data & MEMCG_DATA_OBJCGS) page_memcg_check() returns NULL - for kmem objects (i.e. page->memcg_data & MEMCG_DATA_KMEM) page_memcg_check() returns objcg->memcg - in another cases page_memcg_check() returns page->memcg_data, so for uncharged objects like init_net NULL should be returned. I can introduce exported get_mem_cgroup_from_kmem(), however it should only call mem_cgroup_from_obj(), perhaps under read_rcu_lock/unlock. Do you mean something like this? --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1768,4 +1768,14 @@ static inline struct mem_cgroup *mem_cgroup_from_obj(void *p) #endif /* CONFIG_MEMCG_KMEM */ +static inline struct mem_cgroup *get_mem_cgroup_from_kmem(void *p) +{ + struct mem_cgroup *memcg; + + rcu_read_lock(); + memcg = mem_cgroup_from_obj(p); + rcu_read_unlock(); + + return memcg; +} #endif /* _LINUX_MEMCONTROL_H */ diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index a5b5bb99c644..4003c47965c9 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -26,6 +26,7 @@ #include #include +#include /* * Our network namespace constructor/destructor lists */ @@ -1147,7 +1148,14 @@ static int __register_pernet_operations(struct list_head *list, * setup_net() and cleanup_net() are not possible. */ for_each_net(net) { + struct mem_cgroup *old, *memcg; + + memcg = get_mem_cgroup_from_kmem(net); + if (memcg == NULL) + memcg = root_mem_cgroup; + old = set_active_memcg(memcg); error = ops_init(ops, net); + set_active_memcg(old); if (error) goto out_undo; list_add_tail(&net->exit_list, &net_exit_list);