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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 5D244C11F68 for ; Mon, 12 Jul 2021 16:02:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4ABB360238 for ; Mon, 12 Jul 2021 16:02:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229996AbhGLQFe (ORCPT ); Mon, 12 Jul 2021 12:05:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229465AbhGLQFd (ORCPT ); Mon, 12 Jul 2021 12:05:33 -0400 Received: from mail-ej1-x62b.google.com (mail-ej1-x62b.google.com [IPv6:2a00:1450:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42034C0613DD; Mon, 12 Jul 2021 09:02:44 -0700 (PDT) Received: by mail-ej1-x62b.google.com with SMTP id i20so35573319ejw.4; Mon, 12 Jul 2021 09:02:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yASdFe7xYmlRxSElpuTuPr8cxfmHnIT8PrgFH3o60h4=; b=e+zZayXoNQo9VWz+tZHnI2zHtRNCMfp3pIfi5Sgk53DDp5lpwyHgpSi0jqC/RNPTFV IGXUf+zE54xTsCFnGeZcsN+ShhKmzA3pO76wJIMAuG6qmL9kIQrmrf0grmBREpZMLJjg To09hSnWDZ8uP7RTQKAI9i/847y5ZNK78mm1ojK2ddadyE6kUbTAnewvDPIHdKtGCplQ yJXDbBMti4v30fR0LbhxLXOrEVd7DEaZxzRpzlYeeS+4Ef5SpD00g0DzYMLOlJjKK7kP Uggn265kEF1/Qn4fUdaBGf/yuSww1wD1JjalrwdjXNlQc3kBjyCXLODkS8ToFO7D4Ire k2QA== 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=yASdFe7xYmlRxSElpuTuPr8cxfmHnIT8PrgFH3o60h4=; b=GqI2yNzoLsGF0bg+xTup9TT7urXHv6McH8SUKI5SexXCg80Qs6DmiZKPa74lIcVJWf YluOQLGcVVgCUVVchEoOtATgFZbp432dpf6AgTkRL4spR5VZujrkd/RfzavVqsQ+ap0E dYpgNH/lsgNnNzgVBqR4l3DKq9EXq1gLHuV06AFDbqZ60xs9Q3NEdIr/wV4tVh6mumYZ 1kOqClMxVGWCvhglyo8DyhRBtIKWyrAYotM8WewoPNUdqaDymYQ4R1xIk577lcF+RhQW YoZ0e/2nEpyCF4VWuW+IYMDY+Hi9L+qXNnHbTmKrKlZIolRvza0iagfHLIhBY4wW9CVK Fy2A== X-Gm-Message-State: AOAM531XGVQg4YtlH5u2YUVTzYXNjsJUYP4NIRH5DlYMreL991lkebJ3 ZI+1N9C19937iwoKo5/M0synGXL8f92Jwg2XQ9w= X-Google-Smtp-Source: ABdhPJwzXOENkXmBa4UTeOnWv/u0+TRdQjmXj/CeSutFRfag8CJJciAOdp8+UV+3fzTJqvGysro8BTXgYbLS5P5YDp0= X-Received: by 2002:a17:906:bc2:: with SMTP id y2mr53431206ejg.489.1626105762727; Mon, 12 Jul 2021 09:02:42 -0700 (PDT) MIME-Version: 1.0 References: <1626092196-44697-1-git-send-email-linyunsheng@huawei.com> <1626092196-44697-3-git-send-email-linyunsheng@huawei.com> In-Reply-To: <1626092196-44697-3-git-send-email-linyunsheng@huawei.com> From: Alexander Duyck Date: Mon, 12 Jul 2021 09:02:31 -0700 Message-ID: Subject: Re: [PATCH rfc v3 2/4] page_pool: add interface for getting and setting pagecnt_bias To: Yunsheng Lin Cc: David Miller , Jakub Kicinski , Russell King - ARM Linux , Marcin Wojtas , linuxarm@openeuler.org, yisen.zhuang@huawei.com, Salil Mehta , thomas.petazzoni@bootlin.com, hawk@kernel.org, Ilias Apalodimas , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrew Morton , Peter Zijlstra , Will Deacon , Matthew Wilcox , Vlastimil Babka , fenghua.yu@intel.com, guro@fb.com, Peter Xu , Feng Tang , Jason Gunthorpe , Matteo Croce , Hugh Dickins , Jonathan Lemon , Alexander Lobakin , Willem de Bruijn , wenxu@ucloud.cn, Cong Wang , Kevin Hao , nogikh@google.com, Marco Elver , Yonghong Song , kpsingh@kernel.org, andrii@kernel.org, Martin KaFai Lau , songliubraving@fb.com, Netdev , LKML , bpf Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 12, 2021 at 5:17 AM Yunsheng Lin wrote: > > As suggested by Alexander, "A DMA mapping should be page > aligned anyway so the lower 12 bits would be reserved 0", > so it might make more sense to repurpose the lower 12 bits > of the dma address to store the pagecnt_bias for frag page > support in page pool. > > As newly added page_pool_get_pagecnt_bias() may be called > outside of the softirq context, so annotate the access to > page->dma_addr[0] with READ_ONCE() and WRITE_ONCE(). > > And page_pool_get_pagecnt_bias_ptr() is added to implement > the pagecnt_bias atomic updating when a page is passsed to > the user. > > Other three interfaces using page->dma_addr[0] is only called > in the softirq context during normal rx processing, hopefully > the barrier in the rx processing will ensure the correct order > between getting and setting pagecnt_bias. > > Signed-off-by: Yunsheng Lin > --- > include/net/page_pool.h | 29 +++++++++++++++++++++++++++-- > net/core/page_pool.c | 8 +++++++- > 2 files changed, 34 insertions(+), 3 deletions(-) > > diff --git a/include/net/page_pool.h b/include/net/page_pool.h > index 8d7744d..84cd972 100644 > --- a/include/net/page_pool.h > +++ b/include/net/page_pool.h > @@ -200,17 +200,42 @@ static inline void page_pool_recycle_direct(struct page_pool *pool, > > static inline dma_addr_t page_pool_get_dma_addr(struct page *page) > { > - dma_addr_t ret = page->dma_addr[0]; > + dma_addr_t ret = READ_ONCE(page->dma_addr[0]) & PAGE_MASK; > if (sizeof(dma_addr_t) > sizeof(unsigned long)) > ret |= (dma_addr_t)page->dma_addr[1] << 16 << 16; > return ret; > } > > -static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr) > +static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr) > { > + if (WARN_ON(addr & ~PAGE_MASK)) > + return false; > + > page->dma_addr[0] = addr; > if (sizeof(dma_addr_t) > sizeof(unsigned long)) > page->dma_addr[1] = upper_32_bits(addr); > + > + return true; > +} > + Rather than making this a part of the check here it might make more sense to pull this out and perform the WARN_ON after the check for dma_mapping_error. Also it occurs to me that we only really have to do this in the case where dma_addr_t is larger than the size of a long. Otherwise we could just have the code split things so that dma_addr[0] is the dma_addr and dma_addr[1] is our pagecnt_bias value in which case we could probably just skip the check. > +static inline int page_pool_get_pagecnt_bias(struct page *page) > +{ > + return READ_ONCE(page->dma_addr[0]) & ~PAGE_MASK; > +} > + > +static inline unsigned long *page_pool_pagecnt_bias_ptr(struct page *page) > +{ > + return page->dma_addr; > +} > + > +static inline void page_pool_set_pagecnt_bias(struct page *page, int bias) > +{ > + unsigned long dma_addr_0 = READ_ONCE(page->dma_addr[0]); > + > + dma_addr_0 &= PAGE_MASK; > + dma_addr_0 |= bias; > + > + WRITE_ONCE(page->dma_addr[0], dma_addr_0); > } > > static inline bool is_page_pool_compiled_in(void) > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 78838c6..1abefc6 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -198,7 +198,13 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page) > if (dma_mapping_error(pool->p.dev, dma)) > return false; > So instead of adding to the function below you could just add your WARN_ON check here with the unmapping call. > - page_pool_set_dma_addr(page, dma); > + if (unlikely(!page_pool_set_dma_addr(page, dma))) { > + dma_unmap_page_attrs(pool->p.dev, dma, > + PAGE_SIZE << pool->p.order, > + pool->p.dma_dir, > + DMA_ATTR_SKIP_CPU_SYNC); > + return false; > + } > > if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) > page_pool_dma_sync_for_device(pool, page, pool->p.max_len); > -- > 2.7.4 >