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=-10.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 D64DCC433DF for ; Wed, 15 Jul 2020 15:28:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 917F420663 for ; Wed, 15 Jul 2020 15:28:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=bytedance-com.20150623.gappssmtp.com header.i=@bytedance-com.20150623.gappssmtp.com header.b="DwcwzyBk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 917F420663 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=bytedance.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1CA138D0001; Wed, 15 Jul 2020 11:28:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 17A906B000A; Wed, 15 Jul 2020 11:28:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 041038D0001; Wed, 15 Jul 2020 11:28:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id E068A6B0005 for ; Wed, 15 Jul 2020 11:28:49 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 45A2B8248D51 for ; Wed, 15 Jul 2020 15:28:49 +0000 (UTC) X-FDA: 77040692778.14.fear62_110389926efa Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin14.hostedemail.com (Postfix) with ESMTP id 1476918229835 for ; Wed, 15 Jul 2020 15:28:49 +0000 (UTC) X-HE-Tag: fear62_110389926efa X-Filterd-Recvd-Size: 7505 Received: from mail-pl1-f193.google.com (mail-pl1-f193.google.com [209.85.214.193]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Wed, 15 Jul 2020 15:28:48 +0000 (UTC) Received: by mail-pl1-f193.google.com with SMTP id k4so2518689pld.12 for ; Wed, 15 Jul 2020 08:28:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yg6NTbSkGtSEF4rrYCXrVAXjXqS7dlpNJawysR5Obt4=; b=DwcwzyBkeoGAVivAhQIX1ILJZAxzWHTRHzq3hDK4Qct5A+85N306PVgPU5TI6sH4p4 RtyGFzG2R6Be01CKNJYrfPZtNBBKBfm6m1ePOfDM2q2mcARomxu4KqDiPGvNu0NobTEQ q9TOOuTzjdJRVR/MQfHeyKMkIAT6m2R96v3Lb16YObODRKQq3nq8O2wL8bqaR0Nv6bN7 E4Ka3VtU4XiZSARo9NI77LC52iu5fIcCgwo9d/Qyw+vPSiRZnfS/iBwS9jXQwOXuvWj5 Ny3TWLMHxGi4WUokqI8hPmYhT1AwcTo52U8eNamM6+ZhdrKWBJhruGdBGa69NxabCMAP DlwQ== 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=yg6NTbSkGtSEF4rrYCXrVAXjXqS7dlpNJawysR5Obt4=; b=PPuF7n5BEyaCinrM0Bp0DkZ/1WRqL534xI3UPN2ex6OlFBJkvJV6D/XYqTr3OvIjqI yYmEKAtQNG9VS0FaGeBtYPmCPlosOPyFev3VLEZ/eUSAXCZwxAJBhp+OzCSX8h3PYLLI y7PqJnhmjJ9XHQzbMBG6PFooaIiI8DM1LEsmyNJNvqxsWKrZzBmLQi6kg9W+1awBmMDm xVxlXDj57kwLJ818uwS0QIaQglz4cmDo11y0X2dvwjZYYW/OybCUYqGwVMYVxZPNIEWr P1Nwn/oGZRjJoD8H1gpXhbvnV4AawVVCEyyA02DU8ydWHy4qwaI24EsJp+j66vmUxRmG 20Nw== X-Gm-Message-State: AOAM5337RVeS3ddYGlvhQ7nXTXchZ6u1WWWMUMBy5sxxkabNj+PZYXxg fip3MZc1YrhHYo2MUPeLmT6GJTkq32nRIMi0kE6UiQ== X-Google-Smtp-Source: ABdhPJzOId+r2GHh+iy3UX+vzodA8HqQiE7YfGpNGY3GDVnFlCAkVKSS1N/bVbhlDqE77Ph6vB/UW5Wxa6+kogN0LFk= X-Received: by 2002:a17:90a:20e9:: with SMTP id f96mr171461pjg.13.1594826927168; Wed, 15 Jul 2020 08:28:47 -0700 (PDT) MIME-Version: 1.0 References: <20200707062754.8383-1-songmuchun@bytedance.com> In-Reply-To: From: Muchun Song Date: Wed, 15 Jul 2020 23:28:11 +0800 Message-ID: Subject: Re: [External] Re: [PATCH v5.4.y, v4.19.y] mm: memcg/slab: fix memory leak at non-root kmem_cache destroy To: Shakeel Butt 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: 1476918229835 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 Wed, Jul 15, 2020 at 11:21 PM Shakeel Butt wrote: > > 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). Yeah, here is a typo. I will fix it in the next version patch. > > > 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 > > -- Yours, Muchun