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 AC2DD33030F; Thu, 6 Aug 2026 13:26:02 +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=1786022770; cv=none; b=Qmud6E2fImh35VRi7Q0r5xm5Jm2dqZniRkfFRTRloMY7PV8qv9LVEDSQLRDVSrf4bD51MykFM8GLMZ95pCZegtSZcC7GOya+Bcmhp+DVWupEPMVWNhwdlLZzHxAGQb3/hmDf1jT7DDfulX3tcBbyEFEkDOHnBs9INss2yZLMj48= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786022770; c=relaxed/simple; bh=GpefSc9nAXVeBJnxc9A3kPi/U8ZZGT7MC55eB6f/jWQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SgcIkjXhtofiHYdKAgjtvncSXgLwlbaYdisUBtKRFlqoZEU5vzjdtI2Tgp/8Ib6GwqQJigzWN/APjji9ROPmKzSfTJBQerlW3Gy63RbTzwTraP8iEBRhisTPec7FICYZ4j6xHRh2QOxQUp7bMKBRTcsf629rArk+8u3JS3j8TDE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ITCw7sbp; 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="ITCw7sbp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D45F91F00A3A; Thu, 6 Aug 2026 13:25:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786022760; bh=ExN7aW1e4/LM/S0DFXynYmziaG42HPd3YEBb4sTiQKI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ITCw7sbpr90J19cMvruOSywf8EepUGUHbl0bOFeh30yQ7XpnqbF99F0vPeJk0lJY0 L9imioaC3YRILYr/nVAXmeUm1+TpOnM12Q2SFexH+NawPaY6CMNqE/dGEg9xTVMICw UwUjf63GkTlb+sv38Itzkxn0vF1JvRpj4zSkELroTji9QZJDfr8Uwn63YQ3tA5eNXl KixuXMa2BzFJYAAqCoEwoU8PJtdoTPTin6nPcDEJzsL+TYPtpU3m30pXGK112Oo5rX rkHxPNK7GncJfhIj0qXTe1wkSQNF0Y/ip0JsU3n1HEKx/wTq0SrE+iXfXZfHsj0cpD 7VvHvdJ81mLqg== Message-ID: <82f6afba-756c-4ffd-bd5d-c3432179af28@kernel.org> Date: Thu, 6 Aug 2026 15:25:50 +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 4/4] mm/mempolicy: skip zone device folios when queueing folios To: Gregory Price , linux-mm@kvack.org Cc: damon@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, sj@kernel.org, akpm@linux-foundation.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, vbabka@kernel.org, jannh@google.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com References: <20260728194714.3713735-1-gourry@gourry.net> <20260728194714.3713735-5-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 7/28/26 21:47, Gregory Price wrote: > queue_folios_pte_range() already pairs vm_normal_folio() with an > explicit folio_is_zone_device() check before adding folios to the > migration pagelist. > > vm_normal_folio() alone does not reject zone device memory (a present > device-coherent page in a normal VMA is returned as "normal"). > > Mirror the explicit check in the two other walkers. > > queue_folios_pmd() uses pmd_folio() directly and can encounter a present > zone device PMD - e.g. a device-coherent THP. > > This is not filtered by existing checks: > !pmd_present() - only rejects non-present device-private and > migration entries > > vma_migratable() - excludes DAX and VM_PFNMAP. > > The early return also means such a folio is no longer counted in > qp->nr_failed under MPOL_MF_STRICT. This is the same pattern used > by queue_folios_pte_range() (skipping zone device without failing). > > queue_folios_hugetlb() cannot see zone device memory - hugetlb folios > are never ZONE_DEVICE - so the check there is purely defensive and keeps > all three walkers consistent. > No fixes tag? > Signed-off-by: Gregory Price (Meta) > --- > mm/mempolicy.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 5720f7f54d94..bd79e61a40d1 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -668,6 +668,8 @@ static void queue_folios_pmd(pmd_t *pmd, struct mm_walk *walk) > } > if (!queue_folio_required(folio, qp)) > return; > + if (folio_is_zone_device(folio)) > + return; Why not before the queue_folio_required() check like the PMD case does? > if (!(qp->flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) || > !vma_migratable(walk->vma) || > !migrate_folio_add(folio, qp->pagelist, qp->flags)) > @@ -797,6 +799,8 @@ static int queue_folios_hugetlb(pte_t *pte, unsigned long hmask, > folio = pfn_folio(pte_pfn(ptep)); > if (!queue_folio_required(folio, qp)) > goto unlock; > + if (folio_is_zone_device(folio)) > + goto unlock; Leave the hugetlb part alone. hugetlb folios will never be ZONE_DEVICE. -- Cheers, David