From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E69E2C43334 for ; Sat, 25 Jun 2022 13:54:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4940B8E0030; Sat, 25 Jun 2022 09:54:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4441D8E0009; Sat, 25 Jun 2022 09:54:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30C348E0030; Sat, 25 Jun 2022 09:54:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 2152B8E0009 for ; Sat, 25 Jun 2022 09:54:56 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id E8A49BDA for ; Sat, 25 Jun 2022 13:54:55 +0000 (UTC) X-FDA: 79616904150.28.463080B Received: from mail-vk1-f173.google.com (mail-vk1-f173.google.com [209.85.221.173]) by imf06.hostedemail.com (Postfix) with ESMTP id 92103180007 for ; Sat, 25 Jun 2022 13:54:55 +0000 (UTC) Received: by mail-vk1-f173.google.com with SMTP id b4so2460789vkh.6 for ; Sat, 25 Jun 2022 06:54:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=+DzUTh7oPyYwfjy5rFYKtBOpCrN54eQl+KjUU0VIh5M=; b=C4eCcZabKFsj4hQcQKh7cvv/ikD1fLep7IDkjj0qOpKHWFvWkiSVGrtoCF8WmD2xlX +iBvzDP0SRHu+U/Nczulb41AG/gqJfdt+rFVY27oAuPcQSWB6qpckJbqki5su87EoKgh l/BhWT6JG7B9TDv/ek35oARiUjMULhZaii1LnWeEK0kmm1mX8YmsJBIvA9AfG05hmvJk VMHyuEkt+gYFz4WvIBQQkq+gP8BuEw0snTuJDywL7MC9FrcTbrIeKRtGtN6TstWZgSNm JJfn1X9JjLXvmOen4DlJJb+vIKfNIViBG9ICXcy4xUe4tEx61/Ox9gvdVyrcJeL2np4w 3i4g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+DzUTh7oPyYwfjy5rFYKtBOpCrN54eQl+KjUU0VIh5M=; b=az4PoUPP6TSOy+o3vJhNvu5vvcXvoywWsyM3Aln3mwS07o92ToYG2Fe757FvQOI9Rd yQfJL36Z7qAfUqYnHoQvnqUKAe/WHXaCiTtDJdkK8FL9Hh8zyOBdqEYADpPBFVlgQrpY rLyJE7AGLroHv/ftVEcJ0m2I1qt0PW9igWnPWhnWwqPl4363maOd0vGGo9+GunaLRdnl 8lFyFLmdkCYPZWMK5t/6A1x0T1jk4+XKAdPB8S1VeKZ5DiAnD5etNXG+QRX6mC9tW3XE Dadb9n5udVlO5QxNb0ZHIQaWDiQmnv1yFzGyqiTxs8pbwjdwf39oZDeuxWqFVvIyzuXA 8F3A== X-Gm-Message-State: AJIora/GlVIzWY9O1T1ofy0osB0SqQK8Ue5CcISXv8zdfe94aHGuxg1t GRci3AG9EtPg9TKRZ+Hb2IwSPB3HW1RVGbl6ruA= X-Google-Smtp-Source: AGRyM1vrRDfBHEkvghDMs3K9uonUUXqSV9b0f2DOGVI5iaL7QxKbYHFGCllywnwrOQU/Hs7NLl+LfK+3shinxuYlZ1k= X-Received: by 2002:a1f:a348:0:b0:36f:be56:9381 with SMTP id m69-20020a1fa348000000b0036fbe569381mr437176vke.8.1656165294893; Sat, 25 Jun 2022 06:54:54 -0700 (PDT) MIME-Version: 1.0 References: <20220619155032.32515-1-laoar.shao@gmail.com> <20220619155032.32515-4-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Sat, 25 Jun 2022 21:54:17 +0800 Message-ID: Subject: Re: [RFC PATCH bpf-next 03/10] mm, memcg: Add new helper obj_cgroup_from_current() To: Roman Gushchin Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin Lau , Song Liu , Yonghong Song , john fastabend , KP Singh , Quentin Monnet , Johannes Weiner , Michal Hocko , Shakeel Butt , songmuchun@bytedance.com, Andrew Morton , Christoph Lameter , penberg@kernel.org, David Rientjes , iamjoonsoo.kim@lge.com, Vlastimil Babka , Linux MM , bpf Content-Type: text/plain; charset="UTF-8" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656165295; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=+DzUTh7oPyYwfjy5rFYKtBOpCrN54eQl+KjUU0VIh5M=; b=P2ifBvtTLUDuOl9ROGzkRwKSr4KeL+L2HnZ0Wvi85aTGdnUc1D4TAPk0BIrvP3nxVFzqaM J6IVw1+20/u9TLlyILgU5v8amPHLA4EShZ4K74SRIFh/re2iQCG2+h7eY57Caq7lFF9CcP iM5+0YjRJYM2kYkUqR4s5iwSVK+Z03I= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=C4eCcZab; spf=pass (imf06.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.221.173 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656165295; a=rsa-sha256; cv=none; b=RGyUTYwTbUABWqMWctdyUBqEYycfj6AERAu2Jst0YYSsr/OG3avgg3aOwAnfvleg54VMu6 lKQgSy9XGf+xDL7CtVLfmspuKG+COUPjMVkX0apLQL0gibvSgQWOD/UEp3kci5qgxLwzfn NCyZFuXkXXecByjxn00O7ek+e05T7LY= Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=C4eCcZab; spf=pass (imf06.hostedemail.com: domain of laoar.shao@gmail.com designates 209.85.221.173 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: f7kae1ycwndxdyeck3sk7i4mceorstsy X-Rspamd-Queue-Id: 92103180007 X-HE-Tag: 1656165295-736271 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 23, 2022 at 11:01 AM Roman Gushchin wrote: > > On Sun, Jun 19, 2022 at 03:50:25PM +0000, Yafang Shao wrote: > > The difference between get_obj_cgroup_from_current() and obj_cgroup_from_current() > > is that the later one doesn't add objcg's refcnt. > > > > Signed-off-by: Yafang Shao > > --- > > include/linux/memcontrol.h | 1 + > > mm/memcontrol.c | 24 ++++++++++++++++++++++++ > > 2 files changed, 25 insertions(+) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index cf074156c6ac..402b42670bcd 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -1703,6 +1703,7 @@ bool mem_cgroup_kmem_disabled(void); > > int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order); > > void __memcg_kmem_uncharge_page(struct page *page, int order); > > > > +struct obj_cgroup *obj_cgroup_from_current(void); > > struct obj_cgroup *get_obj_cgroup_from_current(void); > > struct obj_cgroup *get_obj_cgroup_from_page(struct page *page); > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index abec50f31fe6..350a7849dac3 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2950,6 +2950,30 @@ struct obj_cgroup *get_obj_cgroup_from_page(struct page *page) > > return objcg; > > } > > > > +__always_inline struct obj_cgroup *obj_cgroup_from_current(void) > > +{ > > + struct obj_cgroup *objcg = NULL; > > + struct mem_cgroup *memcg; > > + > > + if (memcg_kmem_bypass()) > > + return NULL; > > + > > + rcu_read_lock(); > > + if (unlikely(active_memcg())) > > + memcg = active_memcg(); > > + else > > + memcg = mem_cgroup_from_task(current); > > + > > + for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) { > > + objcg = rcu_dereference(memcg->objcg); > > + if (objcg) > > + break; > > + } > > + rcu_read_unlock(); > > Hm, what prevents the objcg from being released here? Under which conditions > it's safe to call it? obj_cgroup_from_current() is used when we know the objcg's refcnt has already been incremented. For example in my case, it is called after we have already call get_ parent_mem_cgroup(). I should add a comment or a WARN_ON() in this function. -- Regards Yafang