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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27DECC433EF for ; Thu, 19 May 2022 11:10:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237276AbiESLKH (ORCPT ); Thu, 19 May 2022 07:10:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232763AbiESLKF (ORCPT ); Thu, 19 May 2022 07:10:05 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D5D2B042E for ; Thu, 19 May 2022 04:10:04 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4L3n7k23DmzCsmy; Thu, 19 May 2022 19:05:06 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 19 May 2022 19:10:01 +0800 Subject: Re: [PATCH 4/9] mm/z3fold: throw warning on failure of trylock_page in z3fold_alloc To: Vitaly Wool CC: Andrew Morton , Linux-MM , LKML References: <20220429064051.61552-1-linmiaohe@huawei.com> <20220429064051.61552-5-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <28ffb717-a9da-a85f-05a3-300376c3d036@huawei.com> Date: Thu, 19 May 2022 19:10:01 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/5/19 15:10, Vitaly Wool wrote: > On Fri, Apr 29, 2022 at 8:40 AM Miaohe Lin wrote: >> >> If trylock_page fails, the page won't be non-lru movable page. When this >> page is freed via free_z3fold_page, it will trigger bug on PageMovable >> check in __ClearPageMovable. Throw warning on failure of trylock_page to >> guard against such rare case just as what zsmalloc does. > > I don't see how this is better than what we currently have. We can > check if a page is movable before calling __ClearPageMovable instead. Currently the z3fold page (unless headless page) is assumed to be non-lru movable. We will always do __ClearPageMovable in free_z3fold_page which will trigger BUG_ON !PageMovable now. And do you mean we should do something like below ? diff --git a/mm/z3fold.c b/mm/z3fold.c index f41f8b0d9e9a..a244bb5dcb34 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -417,9 +417,10 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless, /* Resets the struct page fields and frees the page */ static void free_z3fold_page(struct page *page, bool headless) { - if (!headless) { + if (likely(__PageMovable(page))) { lock_page(page); - __ClearPageMovable(page); + if (PageMovable(page)) + __ClearPageMovable(page); unlock_page(page); } __free_page(page); Thanks! > > ~Vitaly > >> Signed-off-by: Miaohe Lin >> --- >> mm/z3fold.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/mm/z3fold.c b/mm/z3fold.c >> index 4e6814c5694f..b3b4e65c107f 100644 >> --- a/mm/z3fold.c >> +++ b/mm/z3fold.c >> @@ -1122,10 +1122,9 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, >> __SetPageMovable(page, pool->inode->i_mapping); >> unlock_page(page); >> } else { >> - if (trylock_page(page)) { >> - __SetPageMovable(page, pool->inode->i_mapping); >> - unlock_page(page); >> - } >> + WARN_ON(!trylock_page(page)); >> + __SetPageMovable(page, pool->inode->i_mapping); >> + unlock_page(page); >> } >> z3fold_page_lock(zhdr); >> >> -- >> 2.23.0 >> > . >