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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 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 X-Rspamd-Queue-Id: F0FDE40009 X-Stat-Signature: qshggeds56rt1b88bdhncobz9e5cbncs X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1786022760-238673 X-HE-Meta: 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 5NfA9mQk YnOS+uHeTTqeEwuoS9TRhLkkdUgrCqJEjImjvOsuDltrQIgPMizPIFIjK3pp/r6ESe6Y+c/hQ7etpK45feI7zO347BnEyL+dk14q0DJ2hkCIvuTCbDxnWxvlZ15O7bTbo/hMtxoZwSjRv2jH/UyRY/JNRxZCwWF3yveTIroHla3Gms120GF1SKad+A9MNju6IDSH6OqacaHZj68BQixi+pu1Nq28hmyvPS7WoImJhvRTHledr9dkanrqThQWAEYYFySfKbxQkwzooH7M6E63JLYomaJ8MRfMAFeDOvZgPd1ePDCK6T5ZEqePC1r5PqojjPtVQB3+sq2QJ56zaSDTQo5EbeC/uqqL9W7SGiYNVoyFonypVJaf0FJT+nltoJRtndv2IuUpFis8mCtQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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