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 1844F37DAA2; Thu, 27 Aug 2026 17:05:27 +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=1787850329; cv=none; b=Fycigui5ZGXHA31lSgJFezbXPBERu2FZ1j/NSVXYJYsAOCecM2dxXeuIeShlSfMJW79miC30YY1n9NhWaWaGDtcLylgu3fZBTkAgaGxHjvWlPqJXv1OpiCtThqlGsrnoB1A6vrt5cb2k0gHov0yFB/HWdHg9DOunGIOuRhy2jLk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787850329; c=relaxed/simple; bh=+T3fC1Z2Qq5LFKz9ewfhbuQrC7L3AbjxbqO8cXfLHbk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uVJtE9PCNTJ5t8pMIHojjYdrePaDRTas+ugkSbWUVVU2uctN2Eeg6QJZ+uP/Zrn4rOKuPrp3sHpijEBKd4w8G8K3HqLFbNlcIkbT0jm2nQECxOHxQbGeujl7jLb0fsZEYwsVl+RWLbqRucXSeEfxZgPZaxQXGPGVoQQFLCTecQM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TACTRK+I; 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="TACTRK+I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D953C1F000E9; Thu, 27 Aug 2026 17:05:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787850327; bh=I1lufsy6Im7NFt6gh/akpxHBSyR/Rxm6eWceVNKlW2g=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=TACTRK+IOCMglSMFUPOyndXcTKYnKOgh5FybKkMq9h/FnqoOsf9eibohXzbUoE6kI U+Wk5sA6pKUcf/AmHtw8iWWcCDMPMSjPfikBDWpYsUEFq9xru871uaWIyNMdyfqLxL nku5/C9TzWJM+SzPhRFKwtMfhiOZcK1YDPftnwG6+LxoCw6qRPCkoGAFSuWVSteog3 z+C0wenTac1qFktXGT5JHIBRsbhkgCl8tDM/UVsbmEKyMY+rCQOuzfkKdrQd4fPSsq 8+0U27G5Mt66hdxlP/t/3pk/MWFCTkUOJNnPZ4QVW+qXaY6FpMnmvrVSkAtyFZE5EM 61Sr2IH44g4ug== Message-ID: <6d855beb-1d24-4a6e-ae62-ac9e05e358e5@kernel.org> Date: Thu, 27 Aug 2026 19:05:21 +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 1/2] mm/mempolicy: use vm_normal_folio_pmd() in queue_folios_pmd() 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: <20260821144947.167382-1-gourry@gourry.net> <20260821144947.167382-2-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260821144947.167382-2-gourry@gourry.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/21/26 16:49, Gregory Price wrote: > mmap a VM_PFNMAP region whose ->huge_fault installs a PMD through > vmf_insert_pfn_pmd() - a vfio-pci MMIO BAR does this - then > > mbind(p, len, MPOL_BIND, &mask, maxnode, MPOL_MF_STRICT); > > With a stand-in module for the driver: > > BUG: unable to handle page fault for address: fffff96dc0000008 > RIP: 0010:queue_folios_pte_range+0xaf/0x440 > walk_pgd_range+0x52b/0xaf0 > __walk_page_range+0x6a/0x1d0 > walk_page_range_mm_unsafe+0x193/0x230 > queue_pages_range+0x64/0xa0 > do_mbind+0x25e/0x640 > > queue_folios_pmd(), inlined above, calls pmd_folio() on that PMD. The pfn > is raw MMIO with no memmap entry, so the folio lands in unpopulated > vmemmap. Neither guard stops the walk: > > walk_page_test() skips VM_PFNMAP, but queue_pages_walk_ops > supplies ->test_walk, so it never runs > queue_pages_test_walk() honours vma_migratable(), but only while > MPOL_MF_STRICT is clear > > A VM_MIXEDMAP vma needs neither flag, being vma_migratable(), so plain > mbind(MPOL_MF_MOVE) reaches this too - and there the bad folio carries on > into migrate_folio_add() and folio_isolate_lru(). mshv_vtl_low is such a > mapping. > > Use vm_normal_folio_pmd() and skip on NULL, as the PTE loop in > queue_folios_pte_range() already does with vm_normal_folio(). The huge > zero PMD moves ahead of the lookup, since vm_normal_folio_pmd() returns > NULL for it and its ACTION_CONTINUE would be lost. > > mbind(MPOL_MF_STRICT) over a PMD mapped VM_PFNMAP region now returns 0 > rather than -EIO. The PTE loop already returned 0 there. > > 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 > Assisted-by: Claude:claude-opus-5 > Signed-off-by: Gregory Price (Meta) > --- > mm/mempolicy.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index f1aba551f9f1..85803c845965 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -650,7 +650,8 @@ static inline bool queue_folio_required(struct folio *folio, > return node_isset(nid, *qp->nmask) == !(flags & MPOL_MF_INVERT); > } > > -static void queue_folios_pmd(pmd_t *pmd, struct mm_walk *walk) > +static void queue_folios_pmd(pmd_t *pmd, unsigned long addr, > + struct mm_walk *walk) > { > struct folio *folio; > struct queue_pages *qp = walk->private; > @@ -661,13 +662,15 @@ static void queue_folios_pmd(pmd_t *pmd, struct mm_walk *walk) > qp->nr_failed++; > return; > } > - folio = pmd_folio(pmdval); > - if (folio_is_zone_device(folio)) > - return; > - if (is_huge_zero_folio(folio)) { > + if (is_huge_zero_pmd(pmdval)) { > walk->action = ACTION_CONTINUE; > return; > } > + folio = vm_normal_folio_pmd(walk->vma, addr, pmdval); > + if (!folio) > + return I think this is best written as: folio = vm_normal_folio_pmd(walk->vma, addr, pmdval); if (!folio) { if (is_huge_zero_pmd(pmdval)) { walk->action = ACTION_CONTINUE; return; } return; } That way we minimize checks on the expected path. Acked-by: David Hildenbrand (Arm) -- Cheers, David