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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 4605EC433EF for ; Thu, 23 Sep 2021 11:24:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 132AA611C6 for ; Thu, 23 Sep 2021 11:24:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240611AbhIWLZ7 (ORCPT ); Thu, 23 Sep 2021 07:25:59 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:16378 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240493AbhIWLZ6 (ORCPT ); Thu, 23 Sep 2021 07:25:58 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4HFXl05xFCzRQqh; Thu, 23 Sep 2021 19:20:12 +0800 (CST) Received: from dggpemm500005.china.huawei.com (7.185.36.74) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Thu, 23 Sep 2021 19:24:25 +0800 Received: from [10.69.30.204] (10.69.30.204) by dggpemm500005.china.huawei.com (7.185.36.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.8; Thu, 23 Sep 2021 19:24:25 +0800 Subject: Re: [PATCH net-next 3/7] pool_pool: avoid calling compound_head() for skb frag page To: Ilias Apalodimas CC: , , , , , , , , , , , , , , , , , References: <20210922094131.15625-1-linyunsheng@huawei.com> <20210922094131.15625-4-linyunsheng@huawei.com> From: Yunsheng Lin Message-ID: Date: Thu, 23 Sep 2021 19:24:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 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: [10.69.30.204] X-ClientProxiedBy: dggeme718-chm.china.huawei.com (10.1.199.114) To dggpemm500005.china.huawei.com (7.185.36.74) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2021/9/23 16:33, Ilias Apalodimas wrote: > On Wed, Sep 22, 2021 at 05:41:27PM +0800, Yunsheng Lin wrote: >> As the pp page for a skb frag is always a head page, so make >> sure skb_pp_recycle() passes a head page to avoid calling >> compound_head() for skb frag page case. > > Doesn't that rely on the driver mostly (i.e what's passed in skb_frag_set_page() ? > None of the current netstack code assumes bv_page is the head page of a > compound page. Since our page_pool allocator can will allocate compound > pages for order > 0, why should we rely on it ? As the page pool alloc function return 'struct page *' to the caller, which is the head page of a compound pages for order > 0, so I assume the caller will pass that to skb_frag_set_page(). For non-pp page, I assume it is ok whether the page is a head page or tail page, as the pp_magic for both of them are not set with PP_SIGNATURE. Or should we play safe here, and do the trick as skb_free_head() does in patch 6? > > Thanks > /Ilias >> >> Signed-off-by: Yunsheng Lin >> --- >> include/linux/skbuff.h | 2 +- >> net/core/page_pool.c | 2 -- >> 2 files changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h >> index 6bdb0db3e825..35eebc2310a5 100644 >> --- a/include/linux/skbuff.h >> +++ b/include/linux/skbuff.h >> @@ -4722,7 +4722,7 @@ static inline bool skb_pp_recycle(struct sk_buff *skb, void *data) >> { >> if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle) >> return false; >> - return page_pool_return_skb_page(virt_to_page(data)); >> + return page_pool_return_skb_page(virt_to_head_page(data)); >> } >> >> #endif /* __KERNEL__ */ >> diff --git a/net/core/page_pool.c b/net/core/page_pool.c >> index f7e71dcb6a2e..357fb53343a0 100644 >> --- a/net/core/page_pool.c >> +++ b/net/core/page_pool.c >> @@ -742,8 +742,6 @@ bool page_pool_return_skb_page(struct page *page) >> { >> struct page_pool *pp; >> >> - page = compound_head(page); >> - >> /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation >> * in order to preserve any existing bits, such as bit 0 for the >> * head page of compound page and bit 1 for pfmemalloc page, so >> -- >> 2.33.0 >> > . >