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 061F83C98BA for ; Sat, 10 Oct 2026 20:43:13 +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=1791664995; cv=none; b=SKr8Mo9X6ieQRMH5Y4vupuYBX5k04Azj3UWbR8ULWyReTfLgRFH0KoATw4py4qZFzOpf5wwvaoqmi61S8jl8Nm44+rdTQuktL3zqHFpoBB2aHU3XzFiWhYTyruKsfGOtBYNKFGBDJUU4vW2MO9u0g83aa57rbJOeJWsg+deiTW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791664995; c=relaxed/simple; bh=ZuHpAUhRdRjTZvr8+VGoGbRttg4l6bewAsoGtqxvu6c=; h=Date:To:From:Subject:Message-Id; b=Kdk8W1uCkJt2MHGLBsbaQNSuHdl38jzCXa1dD/UZy2EqaxUzijTR4GlgoDnMUFyUxgsPv4Ef6JbUB/lumfP5NVvXaEqI3GL6tdX+kyRYy14zpzqCya/2e91wg7Swusyl13tE4oHpBozXMgyXAesXBPtUI2FC2xd26KjCWGsMN80= 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=YO8dAMSy; 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="YO8dAMSy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B4511F000FF; Sat, 10 Oct 2026 20:43:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791664993; bh=pOd2qCxudnvkMDZzq45WvGHesIlZOq1jwCTxyJ+5QWE=; h=Date:To:From:Subject; b=YO8dAMSyrtcseUwxCEGI7UNjid0DkoJ47X5vth69Q8H3XzURvn9+b7VlRHorDr9h7 C3JnWzRcfu8BYKptunsGB8K7waMsUBzAhpLgRsagdzJyR80N947ulV98msiQR6Z3z/ ndv7Bn0raLlCu5aXKkySNI0+SfuTH/iv5CA50gyI= Date: Sat, 10 Oct 2026 13:43:12 -0700 To: mm-commits@vger.kernel.org,muchun.song@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-sparse-vmemmap-drop-device-dax-specific-population-path.patch added to mm-unstable branch Message-Id: <20261010204313.5B4511F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/sparse-vmemmap: drop Device DAX-specific population path has been added to the -mm mm-unstable branch. Its filename is mm-sparse-vmemmap-drop-device-dax-specific-population-path.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-sparse-vmemmap-drop-device-dax-specific-population-path.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: Muchun Song Subject: mm/sparse-vmemmap: drop Device DAX-specific population path Date: Sat, 10 Oct 2026 15:57:52 +0800 The common vmemmap path selects the shared page for optimized mappings itself, so Device DAX no longer needs vmemmap_populate_compound_pages() to find a shared tail page and pass its backing PFN through the generic population helpers. Remove the Device DAX-specific population path and let section memmap population always use vmemmap_populate(). The powerpc retains an architecture-specific compound-page implementation, so select it directly from radix__vmemmap_populate() for optimizable sections. Link: https://lore.kernel.org/20261010075755.83339-4-songmuchun@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Reviewed-by: Lance Yang Acked-by: Qi Zheng Cc: Madhavan Srinivasan Cc: Mike Rapoport Cc: David Hildenbrand Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Ritesh Harjani (IBM) Cc: Shrikanth Hegde Cc: Lorenzo Stoakes Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Suren Baghdasaryan Cc: Michal Hocko --- arch/powerpc/mm/book3s64/radix_pgtable.c | 3 mm/mm_init.c | 2 mm/sparse-vmemmap.c | 71 --------------------- 3 files changed, 5 insertions(+), 71 deletions(-) --- a/arch/powerpc/mm/book3s64/radix_pgtable.c~mm-sparse-vmemmap-drop-device-dax-specific-population-path +++ a/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -1126,7 +1126,10 @@ int __meminit radix__vmemmap_populate(un pud_t *pud; pmd_t *pmd; pte_t *pte; + unsigned long pfn = page_to_pfn((struct page *)start); + if (vmemmap_optimizable_order(pfn_to_section_compound_order(pfn))) + return vmemmap_populate_compound_pages(pfn, start, end, node, NULL); /* * If altmap is present, Make sure we align the start vmemmap addr * to PAGE_SIZE so that we calculate the correct start_pfn in --- a/mm/mm_init.c~mm-sparse-vmemmap-drop-device-dax-specific-population-path +++ a/mm/mm_init.c @@ -1046,7 +1046,7 @@ static void zone_device_page_init_from_t * initialize is a lot smaller that the total amount of struct pages being * mapped. This is a paired / mild layering violation with explicit knowledge * of how the sparse_vmemmap internals handle compound pages in the lack - * of an altmap. See vmemmap_populate_compound_pages(). + * of an altmap. */ static inline unsigned long compound_nr_pages(unsigned long pfn, struct dev_pagemap *pgmap) --- a/mm/sparse-vmemmap.c~mm-sparse-vmemmap-drop-device-dax-specific-population-path +++ a/mm/sparse-vmemmap.c @@ -503,71 +503,6 @@ int __meminit vmemmap_populate_hugepages return 0; } -#ifndef vmemmap_populate_compound_pages -/* - * For compound pages bigger than section size (e.g. x86 1G compound - * pages with 2M subsection size) fill the rest of sections as tail - * pages. - * - * Note that memremap_pages() resets @nr_range value and will increment - * it after each range successful onlining. Thus the value or @nr_range - * at section memmap populate corresponds to the in-progress range - * being onlined here. - */ -static bool __meminit reuse_compound_section(unsigned long start_pfn, - struct dev_pagemap *pgmap) -{ - unsigned long nr_pages = pgmap_vmemmap_nr(pgmap); - unsigned long offset = start_pfn - - PHYS_PFN(pgmap->ranges[pgmap->nr_range].start); - - return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION; -} - -static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, - unsigned long start, - unsigned long end, int node, - struct dev_pagemap *pgmap) -{ - const unsigned int order = pfn_to_section_compound_order(start_pfn); - unsigned long size, addr; - pte_t *pte; - struct page *page; - int rc; - - page = vmemmap_shared_tail_page(order, device_zone(node)); - if (!page) - return -ENOMEM; - - if (reuse_compound_section(start_pfn, pgmap)) - return vmemmap_populate_range(start, end, node, NULL, - page_to_pfn(page)); - - size = min(end - start, (1UL << order) * sizeof(struct page)); - for (addr = start; addr < end; addr += size) { - unsigned long next, last = addr + size; - - /* Populate the head page vmemmap page */ - pte = vmemmap_populate_address(addr, node, NULL, -1); - if (!pte) - return -ENOMEM; - - /* - * Reuse the shared page for the rest of tail pages - * See layout diagram in Documentation/mm/vmemmap_dedup.rst - */ - next = addr + PAGE_SIZE; - rc = vmemmap_populate_range(next, last, node, NULL, - page_to_pfn(page)); - if (rc) - return -ENOMEM; - } - - return 0; -} - -#endif - struct page * __meminit __populate_section_memmap(unsigned long pfn, unsigned long nr_pages, int nid, struct vmem_altmap *altmap, struct dev_pagemap *pgmap) @@ -580,11 +515,7 @@ struct page * __meminit __populate_secti !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) return NULL; - if (pgmap && section_vmemmap_optimizable(__pfn_to_section(pfn))) - r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); - else - r = vmemmap_populate(start, end, nid, altmap); - + r = vmemmap_populate(start, end, nid, altmap); if (r < 0) return NULL; _ Patches currently in -mm which might be from muchun.song@linux.dev are mm-sparse-vmemmap-drop-vmemmap_populate_dax.patch mm-sparse-vmemmap-support-device-dax-in-common-vmemmap-path.patch mm-sparse-vmemmap-drop-device-dax-specific-population-path.patch mm-sparse-vmemmap-remove-the-unused-ptpfn-argument.patch mm-sparse-vmemmap-open-code-vmemmap_populate_address.patch mm-mm_init-add-zone-mismatch-warning-during-page-init.patch mm-mm_init-add-zone-mismatch-warning-during-page-init-fix.patch mm-fix-missing-page-table-destructor-in-pagetable_free.patch riscv-mm-fix-hotplug-page-table-destructor-handling.patch riscv-mm-fix-missing-destructor-for-hotplug-pud-tables.patch arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch