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 8EF3734D382; Sat, 8 Nov 2025 01:41:32 +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=1762566092; cv=none; b=In6h+OaaSPuJWJV19fE+fZVYDO7xXXn+PouWwF0r+tcu0JK23Fg81sLjoBobgZ+O5viZPZkWiTKCIVT/ByOg4Q4SnYx7h6/UnE4Q6hXlGhaz2S7TEPj4izTwJcLawKbv+AELOVYoUhtc2wpzpnZ6JCxiya/I/bLNbQb1RQVtY+8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762566092; c=relaxed/simple; bh=bZZGPo2E0msSloBOkeFeACpuzgCC3k9FCP1TtsatxaI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ZpMny9JIwi9mB21/lSlLSVqDUiM1J4g/95dCR11aKuhwrCt4lO/f3ovTEDbNg3zIxXFJDKXRELOWjhvnO600hOJgaCU6fI7cgT8Bn2shwD0xKZ2vdnG7CGlH7T3d6yTz3KKj2TAlA6wfFjxSaOXlZLyjcX3u/+RibP4QPbRfQHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=I4EA2HN1; 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="I4EA2HN1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43EEBC113D0; Sat, 8 Nov 2025 01:41:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762566092; bh=bZZGPo2E0msSloBOkeFeACpuzgCC3k9FCP1TtsatxaI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=I4EA2HN1xggEwDDY+EXXjeuTilUUVALnglQLg5zXBbhd1yvhPoCdwFWeQubJDPAfD y3NuOuh15eivOqBrC5NW9R/erOX2PrG5kdAphHgZAJKLP+tlz7mdlRksYtvMzMJu2X MgvuHswuuxhuknZuovUsvwbX1K0ZS1iaIdOTGnknf0YLeig+4uroSN5muMwksb5JF2 A2f094CKNKnI0a1QHYkgu0hGk7MzhAhRLaFd/TYCSkMsvVcUy7kFVeqROi1LFqezJl M+ZgXQoAm7PEINoyJGzndzB3iHFArwOaWzWRQE/94FXzdWhJ3zwanQ1y/k1CeEVzeu Cc9MjX6Hk5dww== Date: Fri, 7 Nov 2025 17:41:29 -0800 From: Jakub Kicinski To: Byungchul Park 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: <20251107174129.62a3f39c@kernel.org> In-Reply-To: <20251107044708.GA54407@system.software.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> <20251106173320.2f8e683a@kernel.org> <20251107015902.GA3021@system.software.com> <20251106180810.6b06f71a@kernel.org> <20251107044708.GA54407@system.software.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 7 Nov 2025 13:47:08 +0900 Byungchul Park wrote: > The offset of page_type in struct page cannot be used in struct net_iov > for the same purpose, since the offset in struct net_iov is for storing > (struct net_iov_area *)owner. owner does not have to be at a fixed offset. Can we not move owner to _pp_mapping_pad ? Or reorder it with type, enum net_iov_type only has 2 values we can smoosh it with page_type easily. > Yeah, you can tell 'why don't we add the field, page_type, to struct > net_iov (or struct netmem_desc)' so as to be like: > > struct net_iov { > union { > struct netmem_desc desc; > struct > { > unsigned long _flags; > unsigned long pp_magic; > struct page_pool *pp; > unsigned long _pp_mapping_pad; > unsigned long dma_addr; > atomic_long_t pp_ref_count; > + unsigned int page_type; // add this field newly > }; > }; > struct net_iov_area *owner; // the same offet of page_type > enum net_iov_type type; > }; > > I think we can make it anyway but it makes less sense to add page_type > to struct net_iov, only for PGTY_netpp. > > It'd be better to use netmem_desc->pp for that purpose, IMO.