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 07F99402426; Wed, 13 May 2026 12:11:54 +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=1778674315; cv=none; b=C2KkvPybuFBqZp8d2b/cohscS0ywNgxXUVoLnrvBpf+0lvBE10BgDkUK5ZHCYHoFoZz81EwXWkjHsQ/ffLgFKYmqrfjrUTJLkwuGQyK39cUlI4UX7378NtyQLo47uT+LVWbSSSvc1JaewiIUW7G5ZcUTfpGuXb3P1AM/APUH8Z4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778674315; c=relaxed/simple; bh=od6uJlEUQP53Npilyw45Kr3y1pnzvEmpItakHhsQSIQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=E6M+IvHRzqqTu6u2zeJ5j8Um1TQvrCKRId+04TVyXDkFszR5zN1Mt+9Z/T3c6L5LA1XCDij6T31wIv5Jd3Gf1YhBwO2HWB5CKIJ8IPWRBABWaUajK9cZERt4YChlhVANqau31nFPRhTX/G9Tkdey36xLACZpfHllNix8qTOoQYM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=izVWhTpY; 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="izVWhTpY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47ABFC2BCB7; Wed, 13 May 2026 12:11:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778674314; bh=od6uJlEUQP53Npilyw45Kr3y1pnzvEmpItakHhsQSIQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=izVWhTpYPaOzCTITlr/RwH4ln3A/k6VQ8lcK9+9ChdErK39p/svQXKaW8NpVC2tm3 3WARQE87vzjQD0XKFt3D3mOBgBbVVxb65z1w8U9DI49/cd30ILfp9t4Wf973Hma9Ax HfwhUPdZc7UnXG8rPZMxwmfVF+PeduJUkq4uHT4KZu2bB7MSigRvmonJlzcPpjD4mq JKu50ze+mZTY0GDjMIu7CigSffnIzj+k8PJhy/+FUGf3kSLCD7dw/mDZVYGTInbXhK ORXjDbNlHFU9CG6HMC/hjju9EmP1E1xAG4AlgHU/sNR2EbywMmR9NmCbdSQjNF4Ds9 C1prioD/2pBeg== Message-ID: <593851a5-2659-4996-b0f1-7cb8581a9fae@kernel.org> Date: Wed, 13 May 2026 14:11:40 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm: introduce a new page type for page pool in page type To: Dragos Tatulea , Pedro Falcato , "Vlastimil Babka (SUSE)" Cc: Byungchul Park , linux-mm@kvack.org, akpm@linux-foundation.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, kuba@kernel.org, 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, 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 References: <20260224051347.19621-1-byungchul@sk.com> <982b9bc1-0a0a-4fc5-8e3a-3672db2b29a1@nvidia.com> <4af19eda-c29c-4302-92d5-c0915267fc0c@kernel.org> <1817a749-8232-43ab-a0f5-350e5aade235@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/13/26 14:06, Dragos Tatulea wrote: > > > On 13.05.26 11:36, David Hildenbrand (Arm) wrote: >> On 5/13/26 11:26, Pedro Falcato wrote: >>> >>> Yep, you fundamentally can't map a page with a type as page type aliases with >>> mapcount. Even with the given diff, just mapping it will increment the mapcount >>> and wreak havoc. I think we need to revert this patch for now. >>> >>> I'm not sure what the long term plan for this would be. If page types are moved >>> to memdesc types, then the two stop colliding and that could work. I don't know >>> if that's Willy's plan, however. >>> >>> (then there's the other question: are page pool pages really folios? not really. >>> they are mappable, but they aren't part of the page cache, or anon, nor are >>> they in the LRU or have rmap capabilities. perhaps we need a different memdesc >>> for those. we're one step away from reinventing class polymorphism from first >>> principles ;) >> >> Zi Yan is working on this: non-folio pages would no longer mess with >> rmap/mapcounts, and page table walking code will identify them to be non-folio >> things to skip them. >> >> It will take a while, though ... >> > So do I get it right that the path forward here is to revert this commit [1] > and wait until the work from Zi Yan is ready? If there is a requirement that these things will get mapped to user space, then, yes, it currently doesn't work. One could remap_pfn_range() and friends instead, but I assume we don't want to go down that path ... -- Cheers, David