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 1B36D396D36; Sun, 27 Sep 2026 21:46:24 +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=1790545586; cv=none; b=ebTxX1ayGvoUCgQy470/ZwCult80wLVSqOmcBOmVPJ11375PrfGbgR5HVOQBm3qa2g3YpLNaEh4Xberf4RQQIoLo8BdaVZ5hDKFiAoKGQJs3+NvlYMM34VHtSsxJE4ZZn5GniMLsFoOKvbGGZ9Zg/RiVmlmXP//tyKj76QfxlVQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790545586; c=relaxed/simple; bh=g7AvGueYQjO/zSrOBZzi2jw5X0mdhN7wIQ8d/x//kvU=; h=Date:To:From:Subject:Message-Id; b=eavkZjDIoNxhOE7V62d3PlNANi98FoVAWyToeywPaajF4nky/xTwcNYIoHqDC8M5AD0rjRC+MLS4qknTm7uG7qye5kg52lSIXQE2XeYDrm8h8BlBDSn61M8OIPz+e7XCSOfs3vQuBmFEcPos+FT5+G1Z9ELipBEFus7zcbbteas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=s+S4aryL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="s+S4aryL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7F51A1F000FF; Sun, 27 Sep 2026 21:46:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790545584; bh=Mf1GXidq3/SfTJi6BrIvuQ6kcmAZ3OrU3RC6c6NjTfY=; h=Date:To:From:Subject; b=s+S4aryL/GyMp7zM/RJwsnRVtG2wQq7TgjZPhwNNS92g40s/fL0XiA7dtnmUA12bF 6BtYBp28DN8CezSQCk+tegS9N7M78J8FGbNZM4Q6+bD8uonbMd603ZKwQrWeJWhFI+ fnisRcDWx2ERTCGbPDbTlWVptyMSfWqITCQ0QtpQ= Date: Sun, 27 Sep 2026 14:46:24 -0700 To: mm-commits@vger.kernel.org,ziy@nvidia.com,ying.huang@linux.alibaba.com,vbabka@kernel.org,stable@vger.kernel.org,sashiko-bot@kernel.org,rakie.kim@sk.com,peterx@redhat.com,ljs@kernel.org,liam@infradead.org,joshua.hahnjy@gmail.com,jgg@ziepe.ca,jannh@google.com,david@kernel.org,gourry@gourry.net,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd.patch added to mm-unstable branch Message-Id: <20260927214624.7F51A1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/mempolicy: use vm_normal_folio_pmd() in queue_folios_pmd() has been added to the -mm mm-unstable branch. Its filename is mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Gregory Price Subject: mm/mempolicy: use vm_normal_folio_pmd() in queue_folios_pmd() Date: Sat, 26 Sep 2026 06:51:09 -0400 Patch series "mm: stop calling pmd_folio() on special PMDs", v3. Two page table walkers resolve the folio behind a PMD with pmd_folio(), which is only valid for a PMD mapping a refcounted struct page: madvise_cold_or_pageout_pte_range() mm/madvise.c queue_folios_pmd() mm/mempolicy.c vmf_insert_pfn_pmd() installs special PMDs holding a raw pfn that need not have a memmap entry at all. Both walkers can reach one and fault on the first folio field read. The PTE halves of both already use vm_normal_folio(); these two patches make the PMD halves match. The four callers of vmf_insert_pfn_pmd(), and which walker each reaches: drivers/vfio/pci/vfio_pci_core.c VM_PFNMAP mempolicy drivers/gpu/drm/drm_gem_shmem_helper.c VM_PFNMAP mempolicy drivers/gpu/drm/panthor/panthor_gem.c VM_PFNMAP mempolicy drivers/hv/mshv_vtl_main.c VM_MIXEDMAP both can_madv_lru_vma() rejects VM_PFNMAP, so only mshv_vtl_low reaches the madvise walker, and that needs CAP_SYS_ADMIN. queue_pages_walk_ops supplies its own ->test_walk, so walk_page_test()'s generic VM_PFNMAP skip never runs and vfio-pci is reachable by any process holding the device fd. Hence the different stable tags. One behaviour change: mbind(MPOL_MF_STRICT) over a PMD mapped VM_PFNMAP region now returns 0 rather than -EIO. The PTE loop already returned 0 there. drm_gem_shmem and panthor are where this is observable, since they PMD map pages that do have a memmap entry and so never faulted. Reproducer ========== No hardware needed. An out of tree module stands in for the drivers above: three misc devices, each with a ->huge_fault calling vmf_insert_pfn_pmd(), plus VM_HUGEPAGE so the fault path takes the PMD branch. /dev/pmdspec_mixed VM_MIXEDMAP, pfn at the 1 TiB mark, no memmap /dev/pmdspec_pfnmap VM_PFNMAP, pfn at the 1 TiB mark, no memmap /dev/pmdspec_real VM_PFNMAP, real alloc_pages(PMD_ORDER) on node 0 Userspace maps the device into a PMD aligned window, reads one byte to fault the PMD in, checks a module parameter to confirm it went in, then issues the operation. vng --run --user root --memory 4G --verbose \ --append "numa=fake=2" \ --exec "insmod pmdspec.ko && ./pmdspec_test " numa=fake=2 gives a node 1 to bind to; the module allocates its real page on node 0, which is what makes queue_folio_required() true. subtest operation parent series -------------------------------------------------------------------- madv_cold madvise(MADV_COLD) oops ret=0 madv_pageout madvise(MADV_PAGEOUT) oops ret=0 mbind_mixed mbind(MPOL_BIND, n1, MPOL_MF_MOVE) oops ret=0 mbind_pfnmap mbind(MPOL_BIND, n1, MPOL_MF_STRICT) oops ret=0 mbind_real mbind(MPOL_BIND, n1, MPOL_MF_STRICT) -EIO ret=0 Two things the table shows that are easy to miss in the code: - mbind_mixed passes only MPOL_MF_MOVE. MPOL_MF_STRICT is not needed for a VM_MIXEDMAP vma: walk_page_test() only skips VM_PFNMAP, and vma_migratable() is true for VM_MIXEDMAP. - mbind_real demonstrates the user visible change (-EIO -> 0) This patch (of 2): 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(). This also filters the huge zero PMD, so its separate check is no longer needed. mbind(MPOL_MF_STRICT) over a PMD mapped VM_PFNMAP region now returns 0 rather than -EIO. The PTE loop already returned 0 there. Link: https://lore.kernel.org/20260926105110.2156652-1-gourry@gourry.net Link: https://lore.kernel.org/20260926105110.2156652-2-gourry@gourry.net Fixes: 3c8e44c9b369 ("mm: mark special bits for huge pfn mappings when inject") Signed-off-by: Gregory Price (Meta) Signed-off-by: Andrew Morton Reported-by: sashiko-bot Closes: https://sashiko.dev/#/patchset/20260817220810.1175596-1-gourry%40gourry.net Acked-by: David Hildenbrand (Arm) Reviewed-by: Zi Yan Assisted-by: LLM Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Vlastimil Babka Cc: Jann Horn Cc: Joshua Hahn Cc: Rakie Kim Cc: Ying Huang Cc: Peter Xu Cc: Jason Gunthorpe Cc: --- mm/mempolicy.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) --- a/mm/mempolicy.c~mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd +++ a/mm/mempolicy.c @@ -667,7 +667,8 @@ static inline bool queue_folio_required( 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; @@ -678,13 +679,9 @@ static void queue_folios_pmd(pmd_t *pmd, qp->nr_failed++; return; } - folio = pmd_folio(pmdval); - if (folio_is_zone_device(folio)) + folio = vm_normal_folio_pmd(walk->vma, addr, pmdval); + if (!folio || folio_is_zone_device(folio)) return; - if (is_huge_zero_folio(folio)) { - walk->action = ACTION_CONTINUE; - return; - } if (!queue_folio_required(folio, qp)) return; if (!(qp->flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) || @@ -717,7 +714,7 @@ static int queue_folios_pte_range(pmd_t ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { - queue_folios_pmd(pmd, walk); + queue_folios_pmd(pmd, addr, walk); spin_unlock(ptl); goto out; } _ Patches currently in -mm which might be from gourry@gourry.net are mm-mempolicy-take-a-cpuset-cookie-for-the-interleave-node-count.patch mm-mempolicy-use-srcu-for-the-weighted-interleave-state.patch mm-mempolicy-stop-copying-the-nodemask-in-the-interleave-paths.patch mm-huge_memory-skip-zone-device-folios-in-madvise_free_huge_pmd.patch mm-madvise-skip-zone-device-folios-in-cold-pageout-pmd-range.patch mm-mempolicy-skip-zone-device-folios-when-queueing-folios.patch mm-memory_hotplug-factor-out-node_is_memoryless.patch mm-mempolicy-use-vm_normal_folio_pmd-in-queue_folios_pmd.patch mm-madvise-use-vm_normal_folio_pmd-in-cold-pageout-pmd-range.patch mm-refactor-find_next_best_node-to-find_next_best_node_in.patch mm-page_alloc-refactor-build_node_zonelist-out-of-build_zonelists.patch proc-task_mmu-handle-special-pmds-in-clear_refs-and-pagemap.patch mm-madvise-reclaim-isolated-folios-if-pte-restart-fails.patch mm-madvise-use-folio_trylock-in-the-cold-pageout-pmd-split.patch