[PATCH v5 03/12] mm/sparse-vmemmap: introduce CONFIG_VMEMMAP_OPTIMIZATION

[Muchun Song <songmuchun@bytedance.com>]

The section-based vmemmap optimization infrastructure is guarded by
CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP, but it can also be used by
ZONE_DEVICE users that set dev_pagemap::vmemmap_shift. Introduce
CONFIG_VMEMMAP_OPTIMIZATION as a common config for the shared
infrastructure.

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

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
v5:
- Move this patch after the shared tail-page factoring.
- Select VMEMMAP_OPTIMIZATION from ZONE_DEVICE instead of DEV_DAX,
  covering all users of dev_pagemap::vmemmap_shift, reported by
  Sashiko.

v4:
- Rename SPARSEMEM_VMEMMAP_OPTIMIZATION to VMEMMAP_OPTIMIZATION
  (suggested by Mike Rapoport)
- Collect Acked-by from Mike Rapoport

v2:
- Fix SPARSEMEM_VMEMMAP_OPTIMIZATION being selected without SPARSEMEM_VMEMMAP
  reported by Sashiko.
- Add an explicit DEV_DAX dependency on ZONE_DEVICE
- Collect Acked-by from Qi Zheng
---
 arch/x86/entry/vdso/vdso32/fake_32bit_build.h |  2 +-
 fs/Kconfig                                    |  1 +
 include/linux/mm.h                            |  3 +++
 include/linux/mmzone.h                        | 10 +++++-----
 include/linux/page-flags.h                    |  5 ++---
 mm/Kconfig                                    |  5 +++++
 mm/sparse-vmemmap.c                           |  2 +-
 mm/sparse.h                                   |  6 +++---
 8 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
index bc3e549795c3..72a92cb9b53d 100644
--- a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
+++ b/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_VMEMMAP_OPTIMIZATION
 #undef CONFIG_NR_CPUS
 #undef CONFIG_PARAVIRT_XXL
 
diff --git a/fs/Kconfig b/fs/Kconfig
index d1c210c6508f..1454b7fe9641 100644
--- a/fs/Kconfig
+++ b/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 VMEMMAP_OPTIMIZATION
 
 config HUGETLB_PMD_PAGE_TABLE_SHARING
 	def_bool HUGETLB_PAGE
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c49ef99b4413..070ce27e9cd3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5175,6 +5175,9 @@ static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap,
 	unsigned long nr_pages;
 	unsigned long nr_vmemmap_pages;
 
+	if (!IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION))
+		return false;
+
 	if (!pgmap || !is_power_of_2(sizeof(struct page)))
 		return false;
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 68807ff7f946..ee9cbaaa63f4 100644
--- a/include/linux/mmzone.h
+++ b/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_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. */
@@ -1150,7 +1150,7 @@ 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_VMEMMAP_OPTIMIZATION
 	struct page **vmemmap_tails;
 #endif
 } ____cacheline_internodealigned_in_smp;
@@ -2014,7 +2014,7 @@ struct mem_section {
 	unsigned long section_mem_map;
 
 	struct mem_section_usage *usage;
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_VMEMMAP_OPTIMIZATION
 	/*
 	 * Normally, sections hold regular (order-0) pages. However, for
 	 * sections with HVO enabled, this tracks the compound page order
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 86dd0470da11..7080a6a1a79e 100644
--- a/include/linux/page-flags.h
+++ b/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_VMEMMAP_OPTIMIZATION))
 		return false;
 
 	return is_power_of_2(sizeof(struct page));
diff --git a/mm/Kconfig b/mm/Kconfig
index bc7befafb47b..30170a936f1f 100644
--- a/mm/Kconfig
+++ b/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 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.
@@ -1220,6 +1224,7 @@ config ZONE_DMA32
 config ZONE_DEVICE
 	bool "Device memory (pmem, HMM, etc...) hotplug support"
 	depends on MEMORY_HOTREMOVE
+	select VMEMMAP_OPTIMIZATION if ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
 	select XARRAY_MULTI
 
 	help
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 46d9a25b3275..38c36399f53e 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -169,7 +169,7 @@ static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
 	return p;
 }
 
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_VMEMMAP_OPTIMIZATION
 #define VMEMMAP_OPTIMIZATION_NR_ORDERS	(MAX_FOLIO_ORDER - VMEMMAP_OPTIMIZATION_MIN_ORDER + 1)
 
 static __ref struct page **vmemmap_tails_alloc(struct zone *zone)
diff --git a/mm/sparse.h b/mm/sparse.h
index 6e7aaeaa5594..326ad43bb5c3 100644
--- a/mm/sparse.h
+++ b/mm/sparse.h
@@ -10,7 +10,7 @@
 
 #include <linux/mmzone.h>
 
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_VMEMMAP_OPTIMIZATION
 static inline unsigned int section_compound_order(const struct mem_section *section)
 {
 	return section->compound_page_order;
@@ -75,7 +75,7 @@ static inline bool vmemmap_optimizable_pfn(unsigned long pfn)
 
 static inline bool vmemmap_optimizable_order(unsigned int order)
 {
-	if (!IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP))
+	if (!IS_ENABLED(CONFIG_VMEMMAP_OPTIMIZATION))
 		return false;
 
 	if (!is_power_of_2(sizeof(struct page)))
@@ -142,7 +142,7 @@ static inline void sparse_sections_init(void) {}
  * mm/sparse-vmemmap.c
  */
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+#ifdef CONFIG_VMEMMAP_OPTIMIZATION
 struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone);
 #endif
 void sparse_init_subsection_map(void);
-- 
2.54.0