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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 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 X-Rspam-User: X-Rspamd-Queue-Id: BAC59120002 X-Rspamd-Server: rspam04 X-Stat-Signature: bxct9zexw757k9m8btizinxwq3t3qbip X-HE-Tag: 1778674315-605910 X-HE-Meta: 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 XHIdmzBp HZZEHK/oAfSZbqqTFzX4K8NcW9raAOD+jLco2Y4rKv4cHOikQ49NIsVU4D9cxPkWjzC+UCcShmpckU+igzwx6Wepkd8gmvA7DPnXW/tSbZeJh31hV8jo0XzBi9CSNjdqE1MM8jt+k3jUxbmhkIX/9SqoudjjpIux05RpcSJrLGEGuYuLkocnRdVO+3XtVmfTSliCNPxvNeSe5hfaN8Xc/QdiOJ61G5Uj1DOdbdVNHQPct8K21cen3UPLK67FYpS+I1WTTQNauZpR08B0MPM1plZUBPovgOHOaaNxD+Qk3IRxkJgysW/xMEKlvclSpnBkXffimrhEZQJ1e1Z5/aY00e1gfz2s7mR6Z+BMt6/62DqkmKMucG3/5vSUGgQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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