From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E20BB448B8E; Wed, 16 Sep 2026 07:26:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789543588; cv=none; b=Mdvt6TnitcEFJq79Asiq2lPgsQpGkZ+2acMLIJWyDDuCKp2vhxlqDi0PIWA0v+sUP3wsYVxR2M0p+O91cdugWjqEuuLGM+CTZeXy/9zkD0Tn+WzzSBoH8QoTgdwSBMKyJKn7y2HUq47eIAGpOYWSNcOKUJrRaxifpgdprV+uZyw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789543588; c=relaxed/simple; bh=mmdctsfZB8t3ksJTl9790uriRiS9Sn9eRPJmsnyT+lE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rwf9+3o6ermHECOsrG0xDcb/j+ZeSURCCSwnNjF6e4N6hRt973ECTz57sBdgqBxYD+omkOMkZtYW4nfmxW8rLPPE3SYoy+UVQ9L0pT6X5tij/kOR4wrujYq03MzDAzrva1DodZBvg2VaLbk3lXvBZRPS1HN8GdK+LSwp3LSycpI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oJMnzF5C; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oJMnzF5C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF07B1F00893; Wed, 16 Sep 2026 07:26:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789543571; bh=uiduZlpOSzqWe+j41tpJG7GtdSaFaqUdX9h65p2QPhU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=oJMnzF5C7Ev3Dp3N/bV4RJunca3jlNa4TqP6Tj6wD/sqhaf1CRL+n1udXp+dqT4WV eFwQbg8CoIfWO2+GGOfrhngEwutzN69U/TRLUtq6rcLi3SUIlNtU8ZF5YdjTw7ZOob vs7u+mjt807w0erMTUVqxlTY1i1HBswBBh+r0uYT85FpfeFcw3ZdYCFC3vOptMKJaM jlW6tBfOeNLhMb7tU38QVTUhvk4NTCc10iK13orqu2ElcuJ5XW2RGAaMfiG7Ln0yHG ocTNsYde7HHddUhAp2JRBNVWCLB+xGV1aMmukXbGwcBogIQzk/XLcwYOP3uvMGHkhC mreQEkfBjRSkA== Message-ID: <4efdbc78-308f-46cd-ba3d-ae59b53c7ee2@kernel.org> Date: Wed, 16 Sep 2026 09:26:05 +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 v2 2/2] mm/madvise: use vm_normal_folio_pmd() in cold/pageout PMD range To: Gregory Price , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, liam@infradead.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, peterx@redhat.com, jgg@ziepe.ca, sashiko-bot , stable@vger.kernel.org References: <20260912034833.2952750-1-gourry@gourry.net> <20260912034833.2952750-3-gourry@gourry.net> 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 9/12/26 05:48, Gregory Price wrote: > mmap a VM_MIXEDMAP region whose ->huge_fault installs a PMD through > vmf_insert_pfn_pmd() - mshv_vtl_low does this, and needs CAP_SYS_ADMIN > to open - then: > > madvise(p, PMD_SIZE, MADV_PAGEOUT); > > With a stand-in module for the driver: > > BUG: unable to handle page fault for address: fffff587c0000008 > RIP: 0010:madvise_cold_or_pageout_pte_range+0x410/0x9b0 > walk_pgd_range+0x52b/0xaf0 > __walk_page_range+0x6a/0x1d0 > walk_page_range_vma_unsafe+0x8e/0x120 > madvise_pageout+0xb2/0x180 > madvise_vma_behavior+0x46b/0xa90 > do_madvise+0x108/0x190 > __x64_sys_madvise+0x26/0x30 > > Nothing validates the pfn on the way in: > > can_madv_lru_vma() rejects VM_PFNMAP, but not VM_MIXEDMAP > can_fault() *pfn = vmf->pgoff & ~(mask >> PAGE_SHIFT); > vmf_insert_pfn_pmd() no pfn_valid() check > pmd_folio() pfn_to_page() -> unpopulated vmemmap > > Even with a valid pfn the path is wrong. The mapping carries no rmap, so > folio_maybe_mapped_shared() sees mapcount 0, and the walker goes on to > folio_deactivate(), or folio_isolate_lru() plus reclaim_pages(), against a > folio this mapping does not own. > > Use vm_normal_folio_pmd() and skip on NULL, as the PTE half of this same > walker already does with vm_normal_folio(). This also filters the huge > zero PMD, so its separate check is no longer needed. > > Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") > Reported-by: sashiko-bot > Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net > Cc: stable@vger.kernel.org # v6.19+ > Assisted-by: LLM > Signed-off-by: Gregory Price (Meta) > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David