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 AC16451EDEE for ; Wed, 30 Sep 2026 18:40:14 +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=1790793616; cv=none; b=M675dAAIyOQvthVfR+xtbtRDXjQv4Ts34WH7X9VqC4U9eoaSbCNNbwmm+dwrx7XhJpJQS177yPghXekx+EaV+Fx43not3/nJrkdDeZ1pxNjDo9X9bQBSl2uc5H679x1yxskrFgS7fu3eDRaFcAVjjARXZ8nYe+1KSLRBnB9qI2w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793616; c=relaxed/simple; bh=ip08ZaLAZXF+9W+Bnw4c/HozVvNW7WkD1EndOO8G0GY=; h=Date:To:From:Subject:Message-Id; b=ZC8X2CWNyo4y9/18UTLOKQd7/LeheQ4PbqkiqXUv9ANp/jkMIJIKQIfAYDvlB4Q+ARc8VPlIYSO91KWu7yfYh4s3Wzvji+PAi6XH31SJX4aSyBi+76m14hv5LFwnrSKBKQd0/k9NIIIuDRsJj1GlaZNku1BAsD56dOAdEuEz+As= 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=qX5eK3l/; 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="qX5eK3l/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 607351F00899; Wed, 30 Sep 2026 18:40:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790793614; bh=h7mvrxOa2FKOHvMNypnbJ9rBxr86ELUYccdXi3yGTEA=; h=Date:To:From:Subject; b=qX5eK3l/RQ75qAZ2Mryd7cwGqYB33U9Zg/RVf5ED6AaffL8GBPA21NQS68OGyN/3e bNUcdTkoh0lTFNgzRRefxUIdYC6rKBmJblHW1t5NmeU5qUo9F9eeEwlx/GIlzjp6f8 1T12TLuLehwr7Xg+tS7kpVEZXX89euG91GaWqWFQ= Date: Wed, 30 Sep 2026 11:40:14 -0700 To: mm-commits@vger.kernel.org,muchun.song@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages.patch removed from -mm tree Message-Id: <20260930184014.607351F00899@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/sparse-vmemmap: switch device DAX to shared tail vmemmap pages has been removed from the -mm tree. Its filename was mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Muchun Song Subject: mm/sparse-vmemmap: switch device DAX to shared tail vmemmap pages Date: Sun, 27 Sep 2026 10:54:36 +0800 HugeTLB vmemmap optimization now uses per-zone shared tail vmemmap pages. Device DAX has not been switched to that mechanism yet. Switch device DAX to vmemmap_shared_tail_page() as well. This aligns DAX with HugeTLB by using the common per-zone shared tail vmemmap page. The optimization is enabled only for DEV-DAX through pgmap->vmemmap_shift, which supplies the compound page order recorded in section metadata before vmemmap population. Unlike FS-DAX, DEV-DAX does not modify tail struct pages, so sharing them is safe. Since the shared tail page can now back ZONE_DEVICE vmemmap mappings, initialize its entries with PG_reserved for device zones. Also skip poisoning vmemmap-optimizable sections while their struct pages may be shared. Link: https://lore.kernel.org/20260927025441.741633-8-songmuchun@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Acked-by: Qi Zheng Cc: David Hildenbrand Cc: Oscar Salvador Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Jonathan Corbet Cc: Lorenzo Stoakes Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Randy Dunlap Cc: Lance Yang --- include/linux/mmzone.h | 10 ++++++++ mm/memory_hotplug.c | 6 +++- mm/sparse-vmemmap.c | 47 ++++++++++++--------------------------- 3 files changed, 29 insertions(+), 34 deletions(-) --- a/include/linux/mmzone.h~mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/include/linux/mmzone.h @@ -2143,11 +2143,21 @@ static inline int online_device_section( return section && ((section->section_mem_map & flags) == flags); } + +static inline struct zone *device_zone(int nid) +{ + return &NODE_DATA(nid)->node_zones[ZONE_DEVICE]; +} #else static inline int online_device_section(const struct mem_section *section) { return 0; } + +static inline struct zone *device_zone(int nid) +{ + return NULL; +} #endif static inline int online_section_nr(unsigned long nr) --- a/mm/memory_hotplug.c~mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/mm/memory_hotplug.c @@ -43,6 +43,7 @@ #include "mm_init.h" #include "page_alloc.h" #include "shuffle.h" +#include "sparse.h" enum { MEMMAP_ON_MEMORY_DISABLE = 0, @@ -554,8 +555,9 @@ void remove_pfn_range_from_zone(struct z /* Select all remaining pages up to the next section boundary */ cur_nr_pages = min(end_pfn - pfn, SECTION_ALIGN_UP(pfn + 1) - pfn); - page_init_poison(pfn_to_page(pfn), - sizeof(struct page) * cur_nr_pages); + if (!section_vmemmap_optimizable(__pfn_to_section(pfn))) + page_init_poison(pfn_to_page(pfn), + sizeof(struct page) * cur_nr_pages); } /* --- a/mm/sparse-vmemmap.c~mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/mm/sparse-vmemmap.c @@ -221,6 +221,8 @@ struct page __ref *vmemmap_shared_tail_p set_page_node(page, zone_to_nid(zone)); set_page_zone(page, zone_idx(zone)); prep_compound_tail(page, NULL, order); + if (zone_is_zone_device(zone)) + __SetPageReserved(page); } page = virt_to_page(addr); @@ -525,23 +527,6 @@ static bool __meminit reuse_compound_sec return !IS_ALIGNED(offset, nr_pages) && nr_pages > PAGES_PER_SUBSECTION; } -static pte_t * __meminit compound_section_tail_page(unsigned long addr) -{ - pte_t *pte; - - addr -= PAGE_SIZE; - - /* - * Assuming sections are populated sequentially, the previous section's - * page data can be reused. - */ - pte = pte_offset_kernel(pmd_off_k(addr), addr); - if (!pte) - return NULL; - - return pte; -} - static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, unsigned long start, unsigned long end, int node, @@ -551,21 +536,18 @@ static int __meminit vmemmap_populate_co pte_t *pte; int rc; unsigned long flags = VMEMMAP_POPULATE_DAX; + struct page *page; + unsigned int order = pfn_to_section_compound_order(start_pfn); - if (reuse_compound_section(start_pfn, pgmap)) { - pte = compound_section_tail_page(start); - if (!pte) - return -ENOMEM; + page = vmemmap_shared_tail_page(order, device_zone(node)); + if (!page) + return -ENOMEM; - /* - * Reuse the page that was populated in the prior iteration - * with just tail struct pages. - */ + if (reuse_compound_section(start_pfn, pgmap)) return vmemmap_populate_range(start, end, node, NULL, - pte_pfn(ptep_get(pte)), flags); - } + page_to_pfn(page), flags); - size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page)); + size = min(end - start, (1UL << order) * sizeof(struct page)); for (addr = start; addr < end; addr += size) { unsigned long next, last = addr + size; @@ -581,12 +563,12 @@ static int __meminit vmemmap_populate_co return -ENOMEM; /* - * Reuse the previous page for the rest of tail pages + * Reuse the shared page for the rest of tail pages * See layout diagram in Documentation/mm/vmemmap_dedup.rst */ next += PAGE_SIZE; rc = vmemmap_populate_range(next, last, node, NULL, - pte_pfn(ptep_get(pte)), flags); + page_to_pfn(page), flags); if (rc) return -ENOMEM; } @@ -918,13 +900,14 @@ int __meminit sparse_add_section(int nid if (IS_ERR(memmap)) return PTR_ERR(memmap); + ms = __nr_to_section(section_nr); /* * Poison uninitialized struct pages in order to catch invalid flags * combinations. */ - page_init_poison(memmap, sizeof(struct page) * nr_pages); + if (!section_vmemmap_optimizable(ms)) + page_init_poison(memmap, sizeof(struct page) * nr_pages); - ms = __nr_to_section(section_nr); __section_mark_present(ms, section_nr); /* Align memmap to section boundary in the subsection case */ _ Patches currently in -mm which might be from muchun.song@linux.dev are mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages-fix.patch mm-sparse-vmemmap-move-vmemmap-optimization-helpers-to-a-public-header.patch powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch mm-sparse-vmemmap-drop-the-extra-tail-page-from-device-dax-reservation.patch mm-sparse-vmemmap-drop-unused-section_nr_vmemmap_pages-arguments.patch documentation-mm-update-dax-vmemmap-deduplication-docs.patch 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