Re: linux-next: build failure after merge of the akpm-current tree

After merging the akpm-current tree, today's linux-next build (x86_64
allnoconfig) failed like this:

In file included from arch/x86/include/asm/page.h:76,
                 from arch/x86/include/asm/thread_info.h:12,
                 from include/linux/thread_info.h:56,
                 from arch/x86/include/asm/preempt.h:7,
                 from include/linux/preempt.h:78,
                 from include/linux/spinlock.h:51,
                 from include/linux/mmzone.h:8,
                 from include/linux/gfp.h:6,
                 from include/linux/slab.h:15,
                 from include/linux/crypto.h:20,
                 from arch/x86/kernel/asm-offsets.c:9:
include/linux/mm.h: In function 'is_pinnable_page':
include/asm-generic/memory_model.h:64:14: error: implicit declaration of function 'page_to_section'; did you mean 'present_section'? [-Werror=implicit-function-declaration]
   64 |  int __sec = page_to_section(__pg);   \
      |              ^~~~~~~~~~~~~~~
include/asm-generic/memory_model.h:81:21: note: in expansion of macro '__page_to_pfn'
   81 | #define page_to_pfn __page_to_pfn
      |                     ^~~~~~~~~~~~~
include/linux/mm.h:1134:15: note: in expansion of macro 'page_to_pfn'
 1134 |   is_zero_pfn(page_to_pfn(page));
      |               ^~~~~~~~~~~
In file included from include/linux/kallsyms.h:12,
                 from include/linux/bpf.h:21,
                 from include/linux/bpf-cgroup.h:5,
                 from include/linux/cgroup-defs.h:22,
                 from include/linux/cgroup.h:28,
                 from include/linux/memcontrol.h:13,
                 from include/linux/swap.h:9,
                 from include/linux/suspend.h:5,
                 from arch/x86/kernel/asm-offsets.c:13:
include/linux/mm.h: At top level:
include/linux/mm.h:1505:29: error: conflicting types for 'page_to_section'
 1505 | static inline unsigned long page_to_section(const struct page *page)
      |                             ^~~~~~~~~~~~~~~
In file included from arch/x86/include/asm/page.h:76,
                 from arch/x86/include/asm/thread_info.h:12,
                 from include/linux/thread_info.h:56,
                 from arch/x86/include/asm/preempt.h:7,
                 from include/linux/preempt.h:78,
                 from include/linux/spinlock.h:51,
                 from include/linux/mmzone.h:8,
                 from include/linux/gfp.h:6,
                 from include/linux/slab.h:15,
                 from include/linux/crypto.h:20,
                 from arch/x86/kernel/asm-offsets.c:9:
include/asm-generic/memory_model.h:64:14: note: previous implicit declaration of 'page_to_section' was here
   64 |  int __sec = page_to_section(__pg);   \
      |              ^~~~~~~~~~~~~~~
include/asm-generic/memory_model.h:81:21: note: in expansion of macro '__page_to_pfn'
   81 | #define page_to_pfn __page_to_pfn
      |                     ^~~~~~~~~~~~~
include/linux/mm.h:1134:15: note: in expansion of macro 'page_to_pfn'
 1134 |   is_zero_pfn(page_to_pfn(page));
      |               ^~~~~~~~~~~

This build has CONFIG_SPARSEMEM set and CONFIG_SPARSEMEM_VMEMMAP not set.

Caused by commit

  983cb10d3f90 ("mm/gup: do not migrate zero page")

I have applied the following patch for today:

From: Stephen Rothwell <redacted>
Date: Tue, 2 Feb 2021 19:49:00 +1100
Subject: [PATCH] make is_pinnable_page a macro

As it is currently defined before page_to_section() which it needs.

Signed-off-by: Stephen Rothwell <redacted>
---
 include/linux/mm.h | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 58f250cabea6..a608feb0d42e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -1128,11 +1128,9 @@ static inline bool is_zone_movable_page(const struct page *page)
 }
 
 /* MIGRATE_CMA and ZONE_MOVABLE do not allow pin pages */
-static inline bool is_pinnable_page(struct page *page)
-{
-	return !(is_zone_movable_page(page) || is_migrate_cma_page(page)) ||
-		is_zero_pfn(page_to_pfn(page));
-}
+#define is_pinnable_page(page)		\
+	(!(is_zone_movable_page(page) || is_migrate_cma_page(page)) ||	\
+		is_zero_pfn(page_to_pfn(page)))
 
 #ifdef CONFIG_DEV_PAGEMAP_OPS
 void free_devmap_managed_page(struct page *page);

-- 
2.29.2