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 X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2498BC433E6 for ; Wed, 15 Jul 2020 15:21:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D85562065E for ; Wed, 15 Jul 2020 15:21:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="i+pwuqbj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D85562065E Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5001E6B0006; Wed, 15 Jul 2020 11:21:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B0D46B0008; Wed, 15 Jul 2020 11:21:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3C68B6B000A; Wed, 15 Jul 2020 11:21:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0111.hostedemail.com [216.40.44.111]) by kanga.kvack.org (Postfix) with ESMTP id 2793A6B0006 for ; Wed, 15 Jul 2020 11:21:04 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id A13E3181AC9BF for ; Wed, 15 Jul 2020 15:21:03 +0000 (UTC) X-FDA: 77040673206.17.brick74_1c1156426efa Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 70ABF180D0197 for ; Wed, 15 Jul 2020 15:21:03 +0000 (UTC) X-HE-Tag: brick74_1c1156426efa X-Filterd-Recvd-Size: 6948 Received: from mail-lf1-f66.google.com (mail-lf1-f66.google.com [209.85.167.66]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Jul 2020 15:21:02 +0000 (UTC) Received: by mail-lf1-f66.google.com with SMTP id y18so1262499lfh.11 for ; Wed, 15 Jul 2020 08:21:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=vci3IiDcus1RRvUL7DqGs3W5cYFn2DMJGL0yOJaDB2k=; b=i+pwuqbjNy6F6mKzI9aZ/iLrDZ8/ASlBJbGUJl2J22TqFRyEV6tj789yH8T4+HeTOI 5qT/teD0u5tBybu4UG3wSLStTBjk9CXnUor4e6KvOxlpr9fruuL7+rLlYEq+JT8C2G59 8Oey4IfF9j2v3GzDCWPL6e0oUM7uNEmW0KbIB2pppfOhNKLnCaLpvoVjF2hLzFQhMa5j ICU5bLJ+rC7cX28viLeoN+hQFxT4foIyDY9jre1a2xOmHGZ8m+GzbC9T6rJk8G5kUzz6 vYVHeLl9ydpWAnAeUzN5ktKTpFOEBc/H4iwKk28D1ELTDNXNX70N/UKnNzku3K1Xy6Oc eapw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=vci3IiDcus1RRvUL7DqGs3W5cYFn2DMJGL0yOJaDB2k=; b=hOivRGgi05unhtkFuya+r/A2dFZKR/nSIwnFoZB8J2XBPW9bfPLGT0aqEkY1j9RBpE 2PoOgCDrmuclrQtmdP+h1O6tJsjk5j/msLEhSBjge5FICjEoX0LDOI3XdTRyMOqHvAfz ZoIxdQGlqcJAKgmsKlayI1eAQ0BOxboFTXJr/Ow0JScAYTuzuXQztgi/aT8t1laBxT9d EkihRAcCcme2FOTBVlL0+99qF9Yq9z1YVvB0kBQO0PtfyfKK6IgKtjb2o791QTleyU8N jkHm8VGtLO9KsgnCj45mBG/LzLTIIoXcHVWcwExBjLqHXjPTcVbAh2ob8ifq+sh0AJzC kLMA== X-Gm-Message-State: AOAM533gmdsian4FxT5bko/cY5EwRSY1UEmKVqEZbhdE/DleKEu/iPW2 BWElKig9eAGU7nEW0deY3DU3vwupBEmcv/AXTdHdMw== X-Google-Smtp-Source: ABdhPJyHpoLsO0QSFy1u9f3M4Z3AxeoWw12ULRW827C+AuECOOtHfXtEPxIw1DOxBPhrckD3XlBV+y7fFCLbhqOObHM= X-Received: by 2002:a19:e61a:: with SMTP id d26mr5055884lfh.96.1594826461049; Wed, 15 Jul 2020 08:21:01 -0700 (PDT) MIME-Version: 1.0 References: <20200707062754.8383-1-songmuchun@bytedance.com> In-Reply-To: <20200707062754.8383-1-songmuchun@bytedance.com> From: Shakeel Butt Date: Wed, 15 Jul 2020 08:20:49 -0700 Message-ID: Subject: Re: [PATCH v5.4.y, v4.19.y] mm: memcg/slab: fix memory leak at non-root kmem_cache destroy To: Muchun Song Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Linux MM , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 70ABF180D0197 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: Sorry I missed this email. On Mon, Jul 6, 2020 at 11:28 PM Muchun Song wrote: > > If the kmem_cache refcount is greater than one, we should not > mark the root kmem_cache as dying. If we mark the root kmem_cache > dying incorrectly, the non-root kmem_cache can never be destroyed. > It resulted in memory leak when memcg was destroyed. We can use the > following steps to reproduce. > > 1) Use kmem_cache_create() to create a new kmem_cache named A. > 2) Coincidentally, the kmem_cache A is an alias for kmem_cache B, > so the refcount of B is just increased. I definitely missed the alias kmem cache case. > 3) Use kmem_cache_destroy() to destroy the kmem_cache A, just > decrease the B's refcount but mark the B as dying. > 4) Create a new memory cgroup and alloc memory from the kmem_cache > A. It leads to create a non-root kmem_cache for allocating. I think in (4) you meant alloc memory from kmem_cache B instead of A. There should not be any allocation from A after kmem_cache_destroy() in (3). > 5) When destroy the memory cgroup created in the step 4), the > non-root kmem_cache can never be destroyed. > > If we repeat steps 4) and 5), this will cause a lot of memory leak. > So only when refcount reach zero, we mark the root kmem_cache as dying. > > Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate") > Signed-off-by: Muchun Song The patch looks fine. Reviewed-by: Shakeel Butt > --- > mm/slab_common.c | 43 +++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 41 insertions(+), 2 deletions(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 8c1ffbf7de45..83ee6211aec7 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -258,6 +258,11 @@ static void memcg_unlink_cache(struct kmem_cache *s) > list_del(&s->memcg_params.kmem_caches_node); > } > } > + > +static inline bool memcg_kmem_cache_dying(struct kmem_cache *s) > +{ > + return is_root_cache(s) && s->memcg_params.dying; > +} > #else > static inline int init_memcg_params(struct kmem_cache *s, > struct kmem_cache *root_cache) > @@ -272,6 +277,11 @@ static inline void destroy_memcg_params(struct kmem_cache *s) > static inline void memcg_unlink_cache(struct kmem_cache *s) > { > } > + > +static inline bool memcg_kmem_cache_dying(struct kmem_cache *s) > +{ > + return false; > +} > #endif /* CONFIG_MEMCG_KMEM */ > > /* > @@ -326,6 +336,13 @@ int slab_unmergeable(struct kmem_cache *s) > if (s->refcount < 0) > return 1; > > + /* > + * If the kmem_cache is dying. We should also skip this > + * kmem_cache. > + */ > + if (memcg_kmem_cache_dying(s)) > + return 1; > + > return 0; > } > > @@ -944,8 +961,6 @@ void kmem_cache_destroy(struct kmem_cache *s) > if (unlikely(!s)) > return; > > - flush_memcg_workqueue(s); > - > get_online_cpus(); > get_online_mems(); > > @@ -955,6 +970,30 @@ void kmem_cache_destroy(struct kmem_cache *s) > if (s->refcount) > goto out_unlock; > > +#ifdef CONFIG_MEMCG_KMEM > + mutex_unlock(&slab_mutex); > + > + put_online_mems(); > + put_online_cpus(); > + > + flush_memcg_workqueue(s); > + > + get_online_cpus(); > + get_online_mems(); > + > + mutex_lock(&slab_mutex); > + > + if (WARN(s->refcount, > + "kmem_cache_destroy %s: Slab cache is still referenced\n", > + s->name)) { > + /* > + * Reset the dying flag setted by flush_memcg_workqueue(). > + */ > + s->memcg_params.dying = false; > + goto out_unlock; > + } > +#endif > + > err = shutdown_memcg_caches(s); > if (!err) > err = shutdown_cache(s); > -- > 2.11.0 >