From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7AD52355F47; Tue, 17 Mar 2026 09:20:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773739221; cv=none; b=Ddbd9q5PbtBkB/ysZoih+Kq+cG0wKNHPQc2tiImppd7fy4F1dR33LP/CoEhPLE1tdNrx2mnZe2l6eWx36+QePcSZr258lomPIDZ+UfhcTdJWtfHMWujMzPBWXZLf7TFo7tv7LOKoWEsbtqn+54Ilwt/WMkCSwUvWQvk0p7niZRw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773739221; c=relaxed/simple; bh=xP5eeh+0a9lPEEEUwZteoXw337RUHoxL4t15/sE4OyQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=k5bz8A1mUAXNsjcaUJmYP6jjsm/T6HFL+MhKNhIE9TTT5Um9Mo4z0cPzPGh0NF/+ixJEFfwxnV7ttbGPiREmFhPDAu6BgcobvjJ2fDuHfyctOJbrdNssfpFkctCMnxbC9Xlar+rc1OomdisyBIlPG2S95pLfJFxR6hfNtzbnPQY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q3mMbdgS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q3mMbdgS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F197EC4CEF7; Tue, 17 Mar 2026 09:20:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773739220; bh=xP5eeh+0a9lPEEEUwZteoXw337RUHoxL4t15/sE4OyQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Q3mMbdgSSCoLb+Sp3+NLMDtSmduFKJ1HwBvWTNYqaZZrhOMgjV3NLCz+1Mo80CqlV mA2/HTSJXUeM6c/hGvrXdQO3BlsuYbjvXvPYPFXZB81glWCytcEIHBWi58Dk1yXGux wvBrH3ZVkhAo9fxbiWu7TKPHrUaPHgz5VRNHuNoESIhN5sBk4/itodd6tiWozDEb3f sJBxbSQ3etYNS/ptv4SVDIsmTKRDWs6MfUTieQcQVvLcWI71Fa/BZwrrzOJKTbqXhY XUbs8zOP7T+vpbfLLu/MbQ7V61SISUqGtsTc9IFXJKnoFMX+7YRldqFTvi5ou2J/Zm pON1rcXFZLIhA== Message-ID: Date: Tue, 17 Mar 2026 10:20:08 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] mm: introduce a new page type for page pool in page type To: Byungchul Park , linux-mm@kvack.org, akpm@linux-foundation.org, netdev@vger.kernel.org, Jakub Kicinski , Mina Almasry , Toke Hoiland Jorgensen Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, 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, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, almasrymina@google.com, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, sfr@canb.auug.org.au, dw@davidwei.uk, ap420073@gmail.com, dtatulea@nvidia.com References: <20260316222901.GA59948@system.software.com> <20260316223113.20097-1-byungchul@sk.com> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: <20260316223113.20097-1-byungchul@sk.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 16/03/2026 23.31, Byungchul Park wrote: > Currently, the condition 'page->pp_magic == PP_SIGNATURE' is used to > determine if a page belongs to a page pool. However, with the planned > removal of @pp_magic, we should instead leverage the page_type in struct > page, such as PGTY_netpp, for this purpose. > > Introduce and use the page type APIs e.g. PageNetpp(), __SetPageNetpp(), > and __ClearPageNetpp() instead, and remove the existing APIs accessing > @pp_magic e.g. page_pool_page_is_pp(), netmem_or_pp_magic(), and > netmem_clear_pp_magic(). > > Plus, add @page_type to struct net_iov at the same offset as struct page > so as to use the page_type APIs for struct net_iov as well. While at it, > reorder @type and @owner in struct net_iov to avoid a hole and > increasing the struct size. > > This work was inspired by the following link: > > https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com/ > > While at it, move the sanity check for page pool to on the free path. > [...] see below > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 9f2fe46ff69a1..ee81f5c67c18f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1044,7 +1044,6 @@ static inline bool page_expected_state(struct page *page, > #ifdef CONFIG_MEMCG > page->memcg_data | > #endif > - page_pool_page_is_pp(page) | > (page->flags.f & check_flags))) > return false; > > @@ -1071,8 +1070,6 @@ static const char *page_bad_reason(struct page *page, unsigned long flags) > if (unlikely(page->memcg_data)) > bad_reason = "page still charged to cgroup"; > #endif > - if (unlikely(page_pool_page_is_pp(page))) > - bad_reason = "page_pool leak"; > return bad_reason; > } > > @@ -1381,9 +1378,17 @@ __always_inline bool __free_pages_prepare(struct page *page, > mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); > folio->mapping = NULL; > } > - if (unlikely(page_has_type(page))) > + if (unlikely(page_has_type(page))) { > + /* networking expects to clear its page type before releasing */ > + if (is_check_pages_enabled()) { > + if (unlikely(PageNetpp(page))) { > + bad_page(page, "page_pool leak"); > + return false; > + } > + } > /* Reset the page_type (which overlays _mapcount) */ > page->page_type = UINT_MAX; > + } I need some opinions here. When CONFIG_DEBUG_VM is enabled we get help finding (hard to find) page_pool leaks and mark the page as bad. When CONFIG_DEBUG_VM is disabled we silently "allow" leaking. Should we handle this more gracefully here? (release pp resources) Allowing the page to be reused at this point, when a page_pool instance is known to track life-time and (likely) have the page DMA mapped, seems problematic to me. Code only clears page->page_type, but IIRC Toke added DMA tracking in other fields (plus xarray internally). I was going to suggest to simply re-export page_pool_release_page() that was hidden by 535b9c61bdef ("net: page_pool: hide page_pool_release_page()"), but that functionality was lost in 07e0c7d3179d ("net: page_pool: merge page_pool_release_page() with page_pool_return_page()"). (Cc Jakub/Kuba for that choice). Simply page_pool_release_page(page->pp, page). Opinions? --Jesper