Whether the optimized mapping can be used is now decided in the
architecture-specific vmemmap_populate() path. When PowerPC has to fall
back, such as on Hash MMU, it can disable optimization for the populated
vmemmap range there.

Add section_vmemmap_optimization_disable() to centralize this fallback,
use it in the Hash MMU path, and drop the radix-specific
vmemmap_can_optimize() override.

Signed-off-by: Muchun Song <[email protected]>
---
v3:
- Move section_vmemmap_optimization_disable() to mm/sparse-vmemmap.c
  to avoid the LoongArch header dependency (reported by Sashiko)

v2:
- Add section_vmemmap_optimization_disable() for architecture fallbacks
- Use the helper for the PowerPC Hash MMU path
- Include vmemmap-optimization.h directly (reported by Sashiko)
---
 arch/powerpc/include/asm/book3s/64/radix.h |  5 -----
 arch/powerpc/mm/book3s64/radix_pgtable.c   | 10 ----------
 arch/powerpc/mm/init_64.c                  |  2 ++
 include/linux/vmemmap-optimization.h       |  6 ++++++
 mm/sparse-vmemmap.c                        | 17 +++++++++++++++++
 5 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/radix.h 
b/arch/powerpc/include/asm/book3s/64/radix.h
index 8452a2714cb1..df67209b0c5b 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -351,10 +351,5 @@ int radix__create_section_mapping(unsigned long start, 
unsigned long end,
                                  int nid, pgprot_t prot);
 int radix__remove_section_mapping(unsigned long start, unsigned long end);
 #endif /* CONFIG_MEMORY_HOTPLUG */
-
-#ifdef CONFIG_ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
-#define vmemmap_can_optimize vmemmap_can_optimize
-bool vmemmap_can_optimize(struct vmem_altmap *altmap, struct dev_pagemap 
*pgmap);
-#endif
 #endif /* __ASSEMBLER__ */
 #endif
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c 
b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 2924604fbb38..63f369d296b4 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -978,16 +978,6 @@ int __meminit radix__vmemmap_create_mapping(unsigned long 
start,
        return 0;
 }
 
-#ifdef CONFIG_ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
-bool vmemmap_can_optimize(struct vmem_altmap *altmap, struct dev_pagemap 
*pgmap)
-{
-       if (radix_enabled())
-               return __vmemmap_can_optimize(altmap, pgmap);
-
-       return false;
-}
-#endif
-
 int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
                                unsigned long addr, unsigned long next)
 {
diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
index 0e777d7dc332..7329fcacdaf4 100644
--- a/arch/powerpc/mm/init_64.c
+++ b/arch/powerpc/mm/init_64.c
@@ -24,6 +24,7 @@
 #include <linux/types.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
+#include <linux/vmemmap-optimization.h>
 #include <linux/swap.h>
 #include <linux/stddef.h>
 #include <linux/vmalloc.h>
@@ -281,6 +282,7 @@ int __meminit vmemmap_populate(unsigned long start, 
unsigned long end, int node,
        if (radix_enabled())
                return radix__vmemmap_populate(start, end, node, altmap);
 #endif
+       section_vmemmap_optimization_disable(start, end);
 
        return __vmemmap_populate(start, end, node, altmap);
 }
diff --git a/include/linux/vmemmap-optimization.h 
b/include/linux/vmemmap-optimization.h
index 858311a71b0c..22e5a322be0b 100644
--- a/include/linux/vmemmap-optimization.h
+++ b/include/linux/vmemmap-optimization.h
@@ -63,6 +63,7 @@ static inline unsigned int 
pfn_to_section_compound_order(unsigned long pfn)
 }
 
 struct page *vmemmap_shared_tail_page(unsigned int order, struct zone *zone);
+void section_vmemmap_optimization_disable(unsigned long start, unsigned long 
end);
 #else
 static inline unsigned int section_compound_order(const struct mem_section 
*section)
 {
@@ -79,6 +80,11 @@ static inline void section_set_compound_order_range(unsigned 
long pfn,
 {
 }
 
+static inline void section_vmemmap_optimization_disable(unsigned long start,
+               unsigned long end)
+{
+}
+
 static inline unsigned int pfn_to_section_compound_order(unsigned long pfn)
 {
        return 0;
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index b8b55e12f5ba..57aa5c2d8034 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -232,6 +232,23 @@ struct page __ref *vmemmap_shared_tail_page(unsigned int 
order, struct zone *zon
 
        return page;
 }
+
+void __meminit section_vmemmap_optimization_disable(unsigned long start,
+               unsigned long end)
+{
+       unsigned long pfn = page_to_pfn((struct page *)start);
+       unsigned long nr_pages = (end - start) / sizeof(struct page);
+       struct mem_section *section = __pfn_to_section(pfn);
+
+       if (nr_pages < PAGES_PER_SECTION) {
+               VM_WARN_ON_ONCE(section_vmemmap_optimizable(section));
+               return;
+       }
+
+       VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SECTION));
+       VM_WARN_ON_ONCE(nr_pages != PAGES_PER_SECTION);
+       section_set_compound_order(section, 0);
+}
 #endif
 
 static __meminit void *vmemmap_alloc_pte(unsigned long pfn, int node,
-- 
2.54.0


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