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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: D49D8C0013 X-Stat-Signature: wbsfhfdiinkxrb4kipps7dnrhf76q45q X-Rspam-User: X-HE-Tag: 1751038642-488596 X-HE-Meta: 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 JCl10Nuf 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 23.06.25 17:42, Zi Yan wrote: > On 23 Jun 2025, at 11:33, David Hildenbrand wrote: > >> On 18.06.25 20:48, Zi Yan wrote: >>> On 18 Jun 2025, at 14:39, Matthew Wilcox wrote: >>> >>>> On Wed, Jun 18, 2025 at 02:14:15PM -0400, Zi Yan wrote: >>>>> On 18 Jun 2025, at 13:39, David Hildenbrand wrote: >>>>> >>>>>> ... and start moving back to per-page things that will absolutely not be >>>>>> folio things in the future. Add documentation and a comment that the >>>>>> remaining folio stuff (lock, refcount) will have to be reworked as well. >>>>>> >>>>>> While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle >>>>>> it gracefully (relevant with further changes), and convert a >>>>>> WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE(). >>>>> >>>>> The reason is that there is no upstream code, which use movable_ops for >>>>> folios? Is there any fundamental reason preventing movable_ops from >>>>> being used on folios? >>>> >>>> folios either belong to a filesystem or they are anonymous memory, and >>>> so either the filesystem knows how to migrate them (through its a_ops) >>>> or the migration code knows how to handle anon folios directly. >> >> Right, migration of folios will be handled by migration core. >> >>> >>> for device private pages, to support migrating >0 order anon or fs folios >>> to device, how should we represent them for devices? if you think folio is >>> only for anon and fs. >> >> I assume they are proper folios, so yes. Just like they are handled today (-> folios) >> >> I was asking a related question at LSF/MM in Alistair's session: are we sure these things will be folios even before they are assigned to a filesystem? I recall the answer was "yes". >> >> So we don't (and will not) support movable_ops for folios. > > Got it. (I was abusing it to help develop alloc_contig_range() at pageblock > granularity, since it was easy to write a driver to allocate a compound page > at a specific PFN and claim the page is movable, then do page online/offline > the range containing the PFNs. :) ) > > For the patch, Reviewed-by: Zi Yan BTW, thinking about it, I think we could handle compound pages quite easily, we'd just have to lookup the head at some point -- but we wouldn't be using folios for that. BUT, I am note sure how compound pages without a memdesc would look like in a memdesc world, and if it would actually be "compound pages" in the traditional sense. So, I think there would be ways to handle that, once we get to it. -- Cheers, David / dhildenb