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[209.85.220.65]) by mx.google.com with SMTPS id x26sor45770984qvh.63.2019.07.26.16.20.22 for (Google Transport Security); Fri, 26 Jul 2019 16:20:22 -0700 (PDT) Received-SPF: pass (google.com: domain of jwadams@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=kEGHfnb+; spf=pass (google.com: domain of jwadams@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jwadams@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com 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=WuNOArHZs/CiCRyKyjlclGYC7Ncl5iJJmT+ESUl6jAA=; b=kEGHfnb+ky7mAtpgS94T1BlDhXrjAF9XMpWdm7fL5wWt0lI7aJD3/bimEU3aictx5/ /FVoxvjWSJOsaau/ArFWCvjl3UvCYt0UKuqbV3FAYijG3r3NaxbYAKdIv1U91mIBuOWl kovT+dhR3I24/oGuwK8rnhXVMwHQc2af+OjHNTY8E16Znr5UlJcLtWNs1/2WObenCUL6 0XF23LaWT12L30puEcM9OgpjsfeZcqTR9sQGgi8O0ELN4Rr38CxkxB+JwiB78TG4CrBN 8pld23xKRXm20Xxzwcz/LE4LBTuO3cSd5KZ05jAqnl4jlavcMrtBsfAUmwQu1m8TlvJn qLYg== X-Google-Smtp-Source: APXvYqz0xh0QBYyY/zS/kJUsfUUaNRgWxOlmqjlpIVRroO/0xl0eD/u8MIKEBwL+baTN5sYIunTa2DIgnA074DTtHAM= X-Received: by 2002:a0c:b12b:: with SMTP id q40mr71961348qvc.0.1564183221451; Fri, 26 Jul 2019 16:20:21 -0700 (PDT) MIME-Version: 1.0 References: <20190726224810.79660-1-henryburns@google.com> In-Reply-To: <20190726224810.79660-1-henryburns@google.com> From: Jonathan Adams Date: Fri, 26 Jul 2019 16:19:45 -0700 Message-ID: Subject: Re: [PATCH] mm/z3fold.c: Fix z3fold_destroy_pool() ordering To: Henry Burns Cc: Vitaly Vul , Andrew Morton , Shakeel Butt , David Howells , Thomas Gleixner , Al Viro , Linux-MM , LKML , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" 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 Fri, Jul 26, 2019 at 3:48 PM Henry Burns wrote: > > The constraint from the zpool use of z3fold_destroy_pool() is there are no > outstanding handles to memory (so no active allocations), but it is possible > for there to be outstanding work on either of the two wqs in the pool. > > If there is work queued on pool->compact_workqueue when it is called, > z3fold_destroy_pool() will do: > > z3fold_destroy_pool() > destroy_workqueue(pool->release_wq) > destroy_workqueue(pool->compact_wq) > drain_workqueue(pool->compact_wq) > do_compact_page(zhdr) > kref_put(&zhdr->refcount) > __release_z3fold_page(zhdr, ...) > queue_work_on(pool->release_wq, &pool->work) *BOOM* > > So compact_wq needs to be destroyed before release_wq. > > Fixes: 5d03a6613957 ("mm/z3fold.c: use kref to prevent page free/compact race") > > Signed-off-by: Henry Burns Reviewed-by: Jonathan Adams > Cc: > --- > mm/z3fold.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 1a029a7432ee..43de92f52961 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -818,8 +818,15 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool) > { > kmem_cache_destroy(pool->c_handle); > z3fold_unregister_migration(pool); > - destroy_workqueue(pool->release_wq); > + > + /* > + * We need to destroy pool->compact_wq before pool->release_wq, > + * as any pending work on pool->compact_wq will call > + * queue_work(pool->release_wq, &pool->work). > + */ > + > destroy_workqueue(pool->compact_wq); > + destroy_workqueue(pool->release_wq); > kfree(pool); > } > > -- > 2.22.0.709.g102302147b-goog >