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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 87BDA1C000F X-Stat-Signature: zcybf8s4y76zj3rrhhfauj7xwb5gqe7u X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1757346625-662978 X-HE-Meta: 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 uY1b+Vv6 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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 08.09.25 17:46, David Hildenbrand wrote: > On 08.09.25 17:33, Jason Gunthorpe wrote: >> On Mon, Sep 08, 2025 at 05:24:23PM +0200, David Hildenbrand wrote: >>>> >>>>> I think we need to be cautious of scope here :) I don't want to >>>>> accidentally break things this way. >>>> >>>> IMHO it is worth doing when you get into more driver places it is far >>>> more obvious why the VM_SHARED is being checked. >>>> >>>>> OK I think a sensible way forward - How about I add desc_is_cowable() or >>>>> vma_desc_cowable() and only set this if I'm confident it's correct? >>>> >>>> I'm thinking to call it vma_desc_never_cowable() as that is much much >>>> clear what the purpose is. >>> >>> Secretmem wants no private mappings. So we should check exactly that, not >>> whether we might have a cow mapping. >> >> secretmem is checking shared for a different reason than many other places.. > > I think many cases just don't want any private mappings. > > After all, you need a R/O file (VM_MAYWRITE cleared) mapped MAP_PRIVATE > to make is_cow_mapping() == false. Sorry, was confused there. R/O file does not matter with MAP_PRIVATE. I think we default to VM_MAYWRITE with MAP_PRIVATE unless someone explicitly clears it. So in practice there is indeed not a big difference between a private and cow mapping. -- Cheers David / dhildenb