[to-be-updated] mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization.patch removed from -mm tree

[to-be-updated] mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/sparse-vmemmap: introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
has been removed from the -mm tree.  Its filename was
     mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm/sparse-vmemmap: introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
Date: Tue, 8 Sep 2026 11:03:25 +0800

Patch series "mm: Switch device DAX to section-based vmemmap
optimization", v2.

This series is split out from the earlier, larger series "mm: Generalize
HVO for HugeTLB and device DAX" [1].  While the parent series generalizes
vmemmap optimization across HugeTLB and device DAX, this subset addresses
a single, self-contained step: switching device DAX to the section-based
sparse-vmemmap optimization infrastructure introduced for HugeTLB.

After the HugeTLB conversion, optimized vmemmap state is described by the
memory section and the sparse-vmemmap population path can allocate or
reuse shared tail vmemmap pages based on that metadata.  Device DAX still
uses the older DAX-specific population model, including a separate tail
vmemmap page reservation and architecture-specific logic to locate or
populate reusable tail pages.

This series makes device DAX use the same section-based model.  Device DAX
sets the section order from pgmap->vmemmap_shift before vmemmap
population, uses the common per-zone shared tail vmemmap page, and drops
the extra reserved tail page.  The powerpc radix path is updated to use
the same shared tail-page helper, so the generic and powerpc DAX paths
follow the same reservation model.

The first patches prepare the shared infrastructure by introducing a
generic CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION symbol, factoring out shared
tail-page allocation, and keeping the special shared-tail struct page
initialization local to sparse-vmemmap.

The middle patches move device DAX onto that infrastructure by recording
the device DAX compound page order in the memory section, using that
section metadata to back generic device DAX mappings with the common
per-zone shared tail page, exposing the shared helpers so the powerpc
radix path can use the same model, and dropping the extra DAX-only tail
page reservation and the now-unused section accounting arguments.

The final patch updates the documentation for the new DAX layout.

This is intended to be the third smaller step toward the broader HVO
generalization. The wider HVO consolidation between HugeTLB and device
DAX is left for follow-up series.


This patch (of 11):

The section-based vmemmap optimization infrastructure is still guarded by
CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP, but it also can be used by device
DAX.  Introduce CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION as a common config
for the shared infrastructure.

Select the new option from HUGETLB_PAGE_OPTIMIZE_VMEMMAP and from DEV_DAX
when the architecture opts in to DAX vmemmap optimization, and use it to
guard the generic sparse-vmemmap state and helpers.

Link: https://lore.kernel.org/20260908030335.96549-1-songmuchun@bytedance.com
Link: https://lore.kernel.org/20260908030335.96549-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/entry/vdso/vdso32/fake_32bit_build.h |    2 +-
 drivers/dax/Kconfig                           |    2 ++
 fs/Kconfig                                    |    1 +
 include/linux/mm.h                            |    3 +++
 include/linux/mmzone.h                        |   13 +++++++------
 include/linux/page-flags.h                    |    5 ++---
 mm/Kconfig                                    |    4 ++++
 mm/sparse.h                                   |    4 ++--
 8 files changed, 22 insertions(+), 12 deletions(-)

--- a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
@@ -11,7 +11,7 @@
 #undef CONFIG_PGTABLE_LEVELS
 #undef CONFIG_ILLEGAL_POINTER_VALUE
 #undef CONFIG_SPARSEMEM_VMEMMAP
-#undef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#undef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
 #undef CONFIG_NR_CPUS
 #undef CONFIG_PARAVIRT_XXL
 
--- a/drivers/dax/Kconfig~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/drivers/dax/Kconfig
@@ -8,6 +8,8 @@ if DAX
 config DEV_DAX
 	tristate "Device DAX: direct access mapping device"
 	depends on TRANSPARENT_HUGEPAGE
+	depends on ZONE_DEVICE
+	select SPARSEMEM_VMEMMAP_OPTIMIZATION if ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
 	help
 	  Support raw access to differentiated (persistence, bandwidth,
 	  latency...) memory via an mmap(2) capable character
--- a/fs/Kconfig~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/fs/Kconfig
@@ -278,6 +278,7 @@ config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	def_bool HUGETLB_PAGE
 	depends on ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
 	depends on SPARSEMEM_VMEMMAP
+	select SPARSEMEM_VMEMMAP_OPTIMIZATION
 
 config HUGETLB_PMD_PAGE_TABLE_SHARING
 	def_bool HUGETLB_PAGE
--- a/include/linux/mm.h~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/include/linux/mm.h
@@ -5175,6 +5175,9 @@ static inline bool __vmemmap_can_optimiz
 	unsigned long nr_pages;
 	unsigned long nr_vmemmap_pages;
 
+	if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION))
+		return false;
+
 	if (!pgmap || !is_power_of_2(sizeof(struct page)))
 		return false;
 
--- a/include/linux/mmzone.h~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/include/linux/mmzone.h
@@ -102,9 +102,9 @@
  *
  * HVO which is only active if the size of struct page is a power of 2.
  */
-#define MAX_FOLIO_VMEMMAP_ALIGN \
-	(IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP) && \
-	 is_power_of_2(sizeof(struct page)) ? \
+#define MAX_FOLIO_VMEMMAP_ALIGN					\
+	(IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION) &&	\
+	 is_power_of_2(sizeof(struct page)) ?			\
 	 MAX_FOLIO_NR_PAGES * sizeof(struct page) : 0)
 
 /* The number of retained vmemmap pages with HVO enabled. */
@@ -116,7 +116,8 @@
 #define __VMEMMAP_OPTIMIZATION_NR_ORDERS	\
 	(MAX_FOLIO_ORDER - VMEMMAP_OPTIMIZATION_MIN_ORDER + 1)
 #define VMEMMAP_OPTIMIZATION_NR_ORDERS		\
-	(__VMEMMAP_OPTIMIZATION_NR_ORDERS > 0 ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0)
+	((__VMEMMAP_OPTIMIZATION_NR_ORDERS > 0 &&	\
+	  IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION)) ? __VMEMMAP_OPTIMIZATION_NR_ORDERS : 0)
 
 enum migratetype {
 	MIGRATE_UNMOVABLE,
@@ -1155,7 +1156,7 @@ struct zone {
 	/* Zone statistics */
 	atomic_long_t		vm_stat[NR_VM_ZONE_STAT_ITEMS];
 	atomic_long_t		vm_numa_event[NR_VM_NUMA_EVENT_ITEMS];
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
 	struct page *vmemmap_tails[VMEMMAP_OPTIMIZATION_NR_ORDERS];
 #endif
 } ____cacheline_internodealigned_in_smp;
@@ -2019,7 +2020,7 @@ struct mem_section {
 	unsigned long section_mem_map;
 
 	struct mem_section_usage *usage;
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
 	/*
 	 * Normally, sections hold regular (order-0) pages. However, for
 	 * sections with HVO enabled, this tracks the compound page order
--- a/include/linux/page-flags.h~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/include/linux/page-flags.h
@@ -208,14 +208,13 @@ enum pageflags {
 static __always_inline bool compound_info_has_mask(void)
 {
 	/*
-	 * Limit mask usage to HugeTLB vmemmap optimization (HVO) where it
-	 * makes a difference.
+	 * Limit mask usage to HVO where it makes a difference.
 	 *
 	 * The approach with mask would work in the wider set of conditions,
 	 * but it requires validating that struct pages are naturally aligned
 	 * for all orders up to the MAX_FOLIO_ORDER, which can be tricky.
 	 */
-	if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP))
+	if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION))
 		return false;
 
 	return is_power_of_2(sizeof(struct page));
--- a/mm/Kconfig~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/mm/Kconfig
@@ -461,6 +461,10 @@ config SPARSEMEM_VMEMMAP
 	  pfn_to_page and page_to_pfn operations.  This is the most
 	  efficient option when sufficient kernel resources are available.
 
+config SPARSEMEM_VMEMMAP_OPTIMIZATION
+	bool
+	depends on SPARSEMEM_VMEMMAP
+
 #
 # Select this config option from the architecture Kconfig, if it is preferred
 # to enable the feature of HugeTLB/dev_dax vmemmap optimization.
--- a/mm/sparse.h~mm-sparse-vmemmap-introduce-config_sparsemem_vmemmap_optimization
+++ a/mm/sparse.h
@@ -10,7 +10,7 @@
 
 #include <linux/mmzone.h>
 
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION
 static inline unsigned int section_order(const struct mem_section *section)
 {
 	return section->order;
@@ -72,7 +72,7 @@ static inline bool vmemmap_optimizable_p
 
 static inline bool vmemmap_optimizable_order(unsigned int order)
 {
-	if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP))
+	if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP_OPTIMIZATION))
 		return false;
 
 	if (!is_power_of_2(sizeof(struct page)))
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-sparse-relax-struct-mem_section-size-constraints.patch
mm-sparse-vmemmap-rename-hvo-order-macros.patch
mm-mm_init-skip-initializing-shared-vmemmap-tail-pages.patch
mm-sparse-vmemmap-initialize-shared-tail-vmemmap-pages-on-allocation.patch
mm-sparse-vmemmap-support-section-based-vmemmap-accounting.patch
mm-mm_init-factor-out-pfn_to_zone.patch
mm-sparse-vmemmap-move-helpers-ahead-of-future-callers.patch
mm-sparse-vmemmap-support-section-based-vmemmap-optimization.patch
mm-sparse-initialize-memory-sections-earlier.patch
mm-hugetlb-switch-hugetlb-to-section-based-vmemmap-optimization.patch
mm-sparse-vmemmap-remove-sparsemem_vmemmap_preinit-support.patch
mm-sparse-inline-usemap-allocation-into-sparse_init_nid.patch
mm-sparse-remove-section_map_size.patch
mm-hugetlb-remove-huge_bootmem_hvo.patch
mm-hugetlb-remove-huge_bootmem_cma.patch
mm-hugetlb-localize-struct-huge_bootmem_page.patch
mm-hugetlb-localize-huge_bootmem_zones_valid.patch
mm-sparse-vmemmap-factor-out-shared-vmemmap-tail-page-allocation.patch
mm-sparse-vmemmap-open-code-init_compound_tail.patch
mm-sparse-vmemmap-prepare-dax-vmemmap-population-for-section-orders.patch
mm-sparse-vmemmap-set-section-order-for-device-dax.patch
mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages.patch
mm-sparse-vmemmap-move-hvo-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