[PATCH v2] powerpc/s64: Clarify that radix lacks DEBUG_PAGEALLOC

[Joel Stanley <joel@jms.id.au>]

The page_alloc.c code will call into __kernel_map_pages when
DEBUG_PAGEALLOC is configured and enabled.

As the implementation assumes hash, this should crash spectacularly if
not for a bit of luck in __kernel_map_pages. In this function
linear_map_hash_count is always zero, the for loop exits without doing
any damage.

There are no other platforms that determine if they support
debug_pagealloc at runtime. Instead of adding code to mm/page_alloc.c to
do that, this change turns the map/unmap into a noop when in radix
mode and prints a warning once.

Signed-off-by: Joel Stanley <joel@jms.id.au>
---
v2: Put __kernel_map_pages in pgtable.h

 arch/powerpc/include/asm/book3s/64/hash.h    |  2 ++
 arch/powerpc/include/asm/book3s/64/pgtable.h | 11 +++++++++++
 arch/powerpc/include/asm/book3s/64/radix.h   |  3 +++
 arch/powerpc/mm/book3s64/hash_utils.c        |  2 +-
 arch/powerpc/mm/book3s64/radix_pgtable.c     |  7 +++++++
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index d959b0195ad9..674fe0e890dc 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end,
 				 int nid, pgprot_t prot);
 int hash__remove_section_mapping(unsigned long start, unsigned long end);
 
+void hash__kernel_map_pages(struct page *page, int numpages, int enable);
+
 #endif /* !__ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 5d34a8646f08..265661ded238 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -1101,6 +1101,17 @@ static inline void vmemmap_remove_mapping(unsigned long start,
 }
 #endif
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+static inline void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+	if (radix_enabled()) {
+		radix__kernel_map_pages(page, numpages, enable);
+		return;
+	}
+	hash__kernel_map_pages(page, numpages, enable);
+}
+#endif
+
 static inline pte_t pmd_pte(pmd_t pmd)
 {
 	return __pte_raw(pmd_raw(pmd));
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index 59cab558e2f0..d090d9612348 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -316,5 +316,8 @@ 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 */
+
+void radix__kernel_map_pages(struct page *page, int numpages, int enable);
+
 #endif /* __ASSEMBLY__ */
 #endif
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index c145776d3ae5..cfd45245d009 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1988,7 +1988,7 @@ static void kernel_unmap_linear_page(unsigned long vaddr, unsigned long lmi)
 				     mmu_kernel_ssize, 0);
 }
 
-void __kernel_map_pages(struct page *page, int numpages, int enable)
+void hash__kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	unsigned long flags, vaddr, lmi;
 	int i;
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index ae20add7954a..83b33418ad28 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -920,6 +920,13 @@ void __meminit radix__vmemmap_remove_mapping(unsigned long start, unsigned long
 #endif
 #endif
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void radix__kernel_map_pages(struct page *page, int numpages, int enable)
+{
+        pr_warn_once("DEBUG_PAGEALLOC not supported in radix mode\n");
+}
+#endif
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 
 unsigned long radix__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
-- 
2.33.0