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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 559C2C5AE59 for ; Wed, 28 May 2025 08:14:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E6FF36B0093; Wed, 28 May 2025 04:14:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E477D6B0095; Wed, 28 May 2025 04:14:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D842A6B0096; Wed, 28 May 2025 04:14:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B9B556B0093 for ; Wed, 28 May 2025 04:14:14 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by 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Tk4L90eHE/44xS0ola4ckyUUqLiHqhT/A8E4ktcgM50ToxF5yv1K3FvF+E/Sqt7wxXhFLU 6qe3/v7/lO9ldVs8uS6fXYlXUNa8/Hg= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1748420052; a=rsa-sha256; cv=none; b=V9iZs36msTwtQuQDFsCztf23rCMi8tedl/LrF88Z1IYHOLM9CNtrEH7hN7Si/WXOFrq3XS BpomegWipSK4k1NnL1ANmY3cqnUAGQl7bd7erwNU7sWc16BsQrk6L7+fy9rXa9t7Ar8SX7 cQ0H64CIaWNc6VaFAorfmWs5lTl0VqY= X-AuditID: a67dfc5b-681ff7000002311f-e5-6836c5d07935 Date: Wed, 28 May 2025 17:14:03 +0900 From: Byungchul Park To: Pavel Begunkov Cc: Mina Almasry , willy@infradead.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, ilias.apalodimas@linaro.org, harry.yoo@oracle.com, hawk@kernel.org, akpm@linux-foundation.org, davem@davemloft.net, john.fastabend@gmail.com, andrew+netdev@lunn.ch, toke@redhat.com, tariqt@nvidia.com, edumazet@google.com, pabeni@redhat.com, saeedm@nvidia.com, leon@kernel.org, ast@kernel.org, daniel@iogearbox.net, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, vishal.moola@gmail.com Subject: Re: [PATCH 12/18] page_pool: use netmem APIs to access page->pp_magic in page_pool_page_is_pp() Message-ID: <20250528081403.GA28116@system.software.com> References: <20250523032609.16334-1-byungchul@sk.com> <20250523032609.16334-13-byungchul@sk.com> <20250526022307.GA27145@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Se0hTcRTH+e3+7t3daHFbr58JRgsTjJ70ONDDHkQ/iCgQIkqwkZe2mmZb 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 UV1t63c/ aA38aqoAvsaNqv5LAPmX3rcVUAwmy4ThOJ/5T1m8sy8Z+WFIwEJvCbspD5UvSORcAZo2iC/giy7PbkhOFSqB+WTj98Hotf3iZ9L6o5R6bjFuqU7Y1o2gCjsdMjFPvUSZgPLHeu8DD+idiomwQiFkGomU+uy96hIizRZdATmWcqClF1lwlLfRSp47BG57pjerBJ7oIKOIb/7+7OefR6RA0wUQrUIxkNe9P5W15od06DlZSFvI= 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: List-Subscribe: List-Unsubscribe: On Wed, May 28, 2025 at 08:51:47AM +0100, Pavel Begunkov wrote: > On 5/26/25 03:23, Byungchul Park wrote: > > On Fri, May 23, 2025 at 10:21:17AM -0700, Mina Almasry wrote: > > > On Thu, May 22, 2025 at 8:26 PM Byungchul Park wrote: > > > > > > > > To simplify struct page, the effort to seperate its own descriptor from > > > > struct page is required and the work for page pool is on going. > > > > > > > > To achieve that, all the code should avoid accessing page pool members > > > > of struct page directly, but use safe APIs for the purpose. > > > > > > > > Use netmem_is_pp() instead of directly accessing page->pp_magic in > > > > page_pool_page_is_pp(). > > > > > > > > Signed-off-by: Byungchul Park > > > > --- > > > > include/linux/mm.h | 5 +---- > > > > net/core/page_pool.c | 5 +++++ > > > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > > index 8dc012e84033..3f7c80fb73ce 100644 > > > > --- a/include/linux/mm.h > > > > +++ b/include/linux/mm.h > > > > @@ -4312,10 +4312,7 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status); > > > > #define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL) > > > > > > > > #ifdef CONFIG_PAGE_POOL > > > > -static inline bool page_pool_page_is_pp(struct page *page) > > > > -{ > > > > - return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE; > > > > -} > > > > > > I vote for keeping this function as-is (do not convert it to netmem), > > > and instead modify it to access page->netmem_desc->pp_magic. > > > > Once the page pool fields are removed from struct page, struct page will > > have neither struct netmem_desc nor the fields.. > > > > So it's unevitable to cast it to netmem_desc in order to refer to > > pp_magic. Again, pp_magic is no longer associated to struct page. > > > > Thoughts? > > Once the indirection / page shrinking is realized, the page is > supposed to have a type field, isn't it? And all pp_magic trickery > will be replaced with something like > > page_pool_page_is_pp() { return page->type == PAGE_TYPE_PP; } Agree, but we need a temporary solution until then. I will use the following way for now: https://lore.kernel.org/all/20250528051452.GB59539@system.software.com/ Byungchul > > > -- > Pavel Begunkov