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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 89007C433EF for ; Fri, 24 Sep 2021 07:45:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7085A60E94 for ; Fri, 24 Sep 2021 07:45:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244489AbhIXHq7 (ORCPT ); Fri, 24 Sep 2021 03:46:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244473AbhIXHq4 (ORCPT ); Fri, 24 Sep 2021 03:46:56 -0400 Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 048ADC061756 for ; Fri, 24 Sep 2021 00:45:24 -0700 (PDT) Received: by mail-yb1-xb2d.google.com with SMTP id j195so3915332ybj.8 for ; Fri, 24 Sep 2021 00:45:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=VzEkKbf+8GOBCumwF0wyu+zgn/fR7q1MOGRVll1HpEE=; b=Y4P3G7O2QPVN5NTdV1SLpb3F6rsE77Q7DZp7bz5/ghgXpm1L8BiISMMeszO9RShG29 k+a7Wd4hRf1OuhxIIdG26DoE1veD+Tpmd20jFu68xmkzC+xgexUn1QSEf2lAJpxEi+Dm 0OaTyuACM1HcEmaLo3jc/eeWvSbKLl5TmOZ0gRVBi9gjAW/8CwQQ0oUuTXmBsib0P4Ib pDrm3nvOUHgF0HttyvGzrwuncLxJR3ZX9FcfgqOG1/J1umDFy2aKgKxjNBRpFucPoTFI xqnJqgE6uGvgvNZ4VPyHT8dXteYjvgFFZ/N+Uh8Gma01qEs/6b79FsP+3yuBagHr31B4 FQgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=VzEkKbf+8GOBCumwF0wyu+zgn/fR7q1MOGRVll1HpEE=; b=1F3x0Z2etFmNQFY1FCs90Wzygbi3e9IX/uGSHWL0NuH8g2ah1d0JnoXL8X2SGkL/zD jI5PQqqiOHgqcMY3E5X9LT4MHOYxMiCH4h3mTuP5NhPOVR9CQj3K1FIjVQTCX9/WAGwj npRVDD+sFb9VwrdKf7RKEeCKRDNFPXsrOEcNvTxjRsLyDnYos2lewvm+R3PxWUjmd6yF 2kQH/1Pg/HXrPpSGQu/82z5w971qd20aCXeet2I1MuqI7HdtETZp1jt3r7zDQ2CA8rpF 9lQOq8YcrUdHXl0nFBr/39Yw4c3FgYKQ8ftms6OoofAkLITEY/Rg94eNrwcH/dMV/eJu PIfw== X-Gm-Message-State: AOAM531LxwgZ+POGOLvUouQ9psVAJBtFMqIdUjdLIThXGtEa81pOUoFa DE+s7VYfSVK7GQDXZyWkdaPvFWVSvFxjp+MAPtBf6g== X-Google-Smtp-Source: ABdhPJzS21gGDa1XBNNlPYyGIxrKBMF97rw5pxVDQdnj0H1xCXPrLQGbc4IMIgQBPmOHfOa0VImDVu73XqtR/pCZr4g= X-Received: by 2002:a25:2f48:: with SMTP id v69mr10662491ybv.339.1632469523150; Fri, 24 Sep 2021 00:45:23 -0700 (PDT) MIME-Version: 1.0 References: <20210922094131.15625-1-linyunsheng@huawei.com> <20210922094131.15625-4-linyunsheng@huawei.com> <39e62727-6d9f-a0db-39b2-296ebd6972b3@huawei.com> In-Reply-To: <39e62727-6d9f-a0db-39b2-296ebd6972b3@huawei.com> From: Ilias Apalodimas Date: Fri, 24 Sep 2021 10:44:47 +0300 Message-ID: Subject: Re: [PATCH net-next 3/7] pool_pool: avoid calling compound_head() for skb frag page To: Yunsheng Lin Cc: "David S. Miller" , Jakub Kicinski , Networking , open list , linuxarm@openeuler.org, Jesper Dangaard Brouer , Jonathan Lemon , Alexander Lobakin , Willem de Bruijn , Cong Wang , Paolo Abeni , Kevin Hao , Aleksandr Nogikh , Marco Elver , memxor@gmail.com, Eric Dumazet , Alexander Duyck , David Ahern Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 24 Sept 2021 at 10:33, Yunsheng Lin wrote: > > On 2021/9/23 19:47, Ilias Apalodimas wrote: > > On Thu, 23 Sept 2021 at 14:24, Yunsheng Lin wrote: > >> > >> 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(). > > > > Yea that's exactly the assumption I was afraid of. > > Sure not passing the head page might seem weird atm and the assumption > > stands, but the point is we shouldn't blow up the entire network stack > > if someone does that eventually. > > > >> > >> 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. > > > > Yea that's true, although we removed the checking for coalescing > > recyclable and non-recyclable SKBs, the next patch first checks the > > signature before trying to do anything with the skb. > > > >> > >> Or should we play safe here, and do the trick as skb_free_head() does in > >> patch 6? > > > > I don't think the &1 will even be measurable, so I'd suggest just > > dropping this and play safe? > > I am not sure what does '&1' mean above. I meant the check compound_head() is doing before deciding on the head page. > > The one thing I am not sure about the trick done in patch 6 is that > if __page_frag_cache_drain() is right API to use here, I used it because > it is the only API that is expecting a head page. Yea seemed a bit funny to me in the first place, until I figured out what exactly it was doing. Regards /Ilias > > > > > Cheers > > /Ilias > >> > >>> > >>> 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 > >>>> > >>> . > >>> > > . > >