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[211.76.176.103]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f0c30ee4bsm15916663b3a.2.2026.04.14.08.14.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Apr 2026 08:14:52 -0700 (PDT) Message-ID: <6125defb-3aa4-494c-abed-982be684f839@gmail.com> Date: Tue, 14 Apr 2026 23:14:39 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 13/13] mm/huge_memory: add and use has_deposited_pgtable() To: "David Hildenbrand (Arm)" , Lorenzo Stoakes Cc: Andrew Morton , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kiryl Shutsemau , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <41b1ff54-c120-42ae-8b74-54767abf3554@gmail.com> <2f29f66b-46db-4925-b922-4add61b633bf@gmail.com> <53d748d3-4150-4e7b-8c1f-4c58587e9183@kernel.org> Content-Language: en-US From: Yin Tirui In-Reply-To: <53d748d3-4150-4e7b-8c1f-4c58587e9183@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9501E100007 X-Stat-Signature: 6nopoge4nn74j9j4s5swptc7x3xgtqpj X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1776179694-841564 X-HE-Meta: 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 KPS1tXFq 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/14/26 17:44, David Hildenbrand (Arm) wrote: > > I mean, we need some indication to know also during folio splitting > whether we can just discard the PMD, as we can refault it later, or > whether we really have to install a PTE table. > > What if someone used remap_pfn_range() on some part of the VMA, and > faults on another part? > > Doesn't really work. > > Do we have users of remap_pfn_range() that have ->fault set? If not, we > should probably just disallow this combination. I did a quick tree-wide grep: $ git grep -l "remap_pfn_range" | xargs grep -l "\.fault\s*=" arch/powerpc/platforms/book3s/vas-api.c drivers/infiniband/hw/hfi1/file_ops.c drivers/uio/uio.c drivers/vfio/pci/vfio_pci_core.c fs/proc/vmcore.c security/selinux/selinuxfs.c It turns out there are two users of this "hybrid" approach in the kernel: 1. fs/proc/vmcore.c: It pre-maps via remap_pfn_range() but registers mmap_vmcore_fault(). 2. arch/powerpc/platforms/book3s/vas-api.c: It pre-maps via remap_pfn_range(), but registers vas_mmap_fault(). > > Then we know for sure whether something was installed through > remap_pfn_range() or through a fault handler. > How would you suggest we proceed here? -- Yin Tirui