From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.skhynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EB8D233993; Fri, 7 Nov 2025 01:59:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762480763; cv=none; b=js5SdOC4AiJJ/U1KLJS4EE88TTriKPktADLg2XZdS1o52LzKQcZnYsU+JbpACKIF8uPpNLGozTRuMKjG8eCmVhKBy9i6/qIUfrs9L5t1iwDDOTSgPvborLcw6FVK+xO9c0RUImOiWRPXw1sChZE+y4knlXnBVLEjcFuCtkSUO1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762480763; c=relaxed/simple; bh=7DAjkr9cSxRS0fZbyexesbeKd4d8lXU4RfB66rg63DY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fVhEPUdk1/VkP86IzN3nZN8rSyIaxeVS8L91qEZtsKMekNTi3nSH4cQXRd8fiLKpIs7BWvq/aPFhSkJTvIR0eJVvBs6D+AxxY3ii0GTBxXAl2TXAF6XxPTn9JCJryj16irXKOftCfdYdiuYdH7hA3KB+IIBEtGHddSSncip8N3c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-c45ff70000001609-41-690d526b4ee5 Date: Fri, 7 Nov 2025 10:59:02 +0900 From: Byungchul Park To: Jakub Kicinski Cc: linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, hawk@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, akpm@linux-foundation.org, 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 Subject: Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as page pool for net_iov not page-backed Message-ID: <20251107015902.GA3021@system.software.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> <20251106173320.2f8e683a@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251106173320.2f8e683a@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0iTYRTHefZeHY5eV+ZT9mkFkZXaKjpBFwmKByKQpA9dqEZ70eFctZlp EGw1yCLNlZLOBbPwbhmzdFqW6dQsupnF201tVlIts1XiUrI5k/r2439+/M/5cHhKeZ+Zy+sM 6aLRoNGrWDkt/xJesjR1q0IX3z6wBBy1NSxUj2ZCeb+bgUDNoAwcVfUIfgRecTDR3IHgu6eT hc9tfgSXSkYocDyy0vCz9hcFjU2DCD4VXmbhfYeXg2rXFugr+0DDzRMNFHjP3GUhxzpGQXNg iINj7opgcZ2Zg8f1uQzk/yqloMHcz8HTJgcLvTUTDHxozaGhy15Jw3CBh4K+3ATocM6Gkfs+ BJ7aBhmMnL7AwrOiJhlcb37GwbluJwsD1j4E3W1eGgrGs1kotuQiGBsNVg7l/WCguL2XS4gl FkliSZvvK0WuVb6QkeeFNppIt+7JSKP9DUecrkOkriKGnJK6KeKqOskSl/8sR14/v8mSu4Vj NGl8u5o0ur/LSM7xITYxcod8jVbU6zJEY9y6vfKUHlsBe8DGZeaP25AZ3WNOoTAeCyuwK2dC Ns21Te30JNPCAux5UB5yWGEhlqQANcmzgrm1rijoyHlKGOZwodQbkmYK6Xj4qzkkKYRV2Ho+ LyQphWyEzdceMlODCNxV9C60gRJisPT7Y3AzH+RoXP6bn4zDhGX4ZbGDneRIYT5uqe/8e5yP x/mWGVM8B9+pkOg8JNj/a7X/12r/1+pEVBVS6gwZaRqdfkVsSpZBlxm7b3+aCwVfrOzo+E43 8j9OakUCj1ThitFb4Tolo8kwZaW1IsxTqlmKlYZgpNBqso6Ixv17jIf0oqkVRfO0KkqhHjms VQrJmnQxVRQPiMbpqYwPm2tGmgfmnuNnH+0+mKdUETG6M/lKbkJWqbp90TxjprZgV+CqN25V Mlg4v9q9zdG1vqpF/T4+sNvmWxvYbsIZzVe615c7xMhPzprEj6hoMEq/9kZSqSsqgvHoTu7t SWiJ3vBtw4zhMt/yJ/HC6ZLs253ezUcXL9940Q91WvVLQJtUtClFsyyGMpo0fwAGlwewXgMA AA== X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTYRjHe8/lPcfh4qRWh4KIGUiCWVD0RFFSVC/dCUGoD7Xy1MZ05bZE g2DmoJI0V4pzrrKrl6zBNJ2SEc57mKVmxywty6Iys1ymadpcRH378/tfni8PTwfdYefxWr1J MujVcSqsYBQ7VqdG6HYrtUsbh4PB4SzBcGs0CQpeuVkYK3lPgaO4HIF3rJuDqep6BMO1DRg+ eb4huHZlhAZHq4WB786fNFRWvUfw0XYbQ399Hwe3XNuh9+Y7Bu6dqqCh71wjhnTLOA3VY4Mc nHQX+oZLzRx4Ljax8Lg8g4WsnzdoqDC/4qC9yoGhp2SKhXc16Qw02YsYGMqupaE3Iwrq8+fA yMMBBLXOCgpGzl7E8DS3ioK71U85uNCWj+GNpRdBm6ePgeyJ0xjyUjIQjI/6JgczvSzk1fVw UZEkRZYx8Qx8oUlZURdFOm1Whsj3mylSaX/JkXzXMVJaGE7S5DaauIrPYOL6dp4jLzrvYdJo G2dI5etVpNI9TJH01EG8a84exZpYKU6bKBki1+5XaDqs2fiolUvKmrAiM2pm01AALwrLRWdV HTOtGWGRWNtS4OdYCBNleYye1iE+binN9WUUPC0McaJN7vGHggWTOPTF7A8phZWiJSfTHwoS TiPRXPaI/WPMEpty3/ov0EK4KE9+oNIQ79PzxYJJfhoHCMvE53kOPK1nC6Hig/IGKhMp7f+1 7f+17f/a+YguRiFafWK8Whu3YolRp0nWa5OWHDwS70K+L7p5YsLqRt72zTVI4JEqUDl6P1Ab xKoTjcnxNUjkaVWIcoXeh5Sx6uTjkuHIPsOxOMlYg+bzjGquckuMtD9IOKw2STpJOioZ/roU HzDPjCIWShFXTZrV/S11V36sD5W6Cp1FXMZXnRT941JMk+34rkMm3PU46xfbfHiGl3q9lcR0 5CRulDXrLjNbyg3DmxIGPd0fo9PDnsxMeNbxxjip++wZMMd+bd0bvKAl8nNdf1H71uvRoTsD E8qiFk+JYQeuP8nZcMZeuC0l1W2n12CvijFq1MvCaYNR/RuahmFKQQMAAA== X-CFilter-Loop: Reflected On Thu, Nov 06, 2025 at 05:33:20PM -0800, Jakub Kicinski wrote: > On Mon, 3 Nov 2025 16:51:07 +0900 Byungchul Park wrote: > > However, for net_iov not ^ *not* page-backed > > page-backed, the identification cannot be based on the page_type. > > Instead, nmdesc->pp can be used to see if it belongs to a page pool, by > > making sure nmdesc->pp is NULL otherwise. > > Please explain why. Isn't the type just a value in a field? > Which net_iov could also set accordingly.. ? page_type field is in 'struct page', so 'struct page' can check the type. However, the field is not in 'struct net_iov', so 'struct net_iov' that is not backed by page, cannot use the type checking to see if it's page pool'ed instance. I'm afraid I didn't get your questions. I will try to explain again properly if you give me more detail and example about your questions or requirement. Byungchul