mm: fix phys_to_target_node() and memory_add_physaddr_to_nid() exports

The core-mm has a default __weak implementation of phys_to_target_node()
to mirror the weak definition of memory_add_physaddr_to_nid().  That
symbol is exported for modules.  However, while the export in
mm/memory_hotplug.c exported the symbol in the configuration cases of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=y

...and:

	CONFIG_NUMA_KEEP_MEMINFO=n
	CONFIG_MEMORY_HOTPLUG=y

...it failed to export the symbol in the case of:

	CONFIG_NUMA_KEEP_MEMINFO=y
	CONFIG_MEMORY_HOTPLUG=n

Not only is that broken, but Christoph points out that the kernel should
not be exporting any __weak symbol, which means that
memory_add_physaddr_to_nid() example that phys_to_target_node() copied
is broken too.

Rework the definition of phys_to_target_node() and
memory_add_physaddr_to_nid() to not require weak symbols.  Move to the
common arch override design-pattern of an asm header defining a symbol
to replace the default implementation.

The only common header that all memory_add_physaddr_to_nid() producing
architectures implement is asm/sparsemem.h.  In fact, powerpc already
defines its memory_add_physaddr_to_nid() helper in sparsemem.h.
Double-down on that observation and define phys_to_target_node() where
necessary in asm/sparsemem.h.  An alternate consideration that was
discarded was to put this override in asm/numa.h, but that entangles
with the definition of MAX_NUMNODES relative to the inclusion of
linux/nodemask.h, and requires powerpc to grow a new header.

The dependency on NUMA_KEEP_MEMINFO for DEV_DAX_HMEM_DEVICES is invalid
now that the symbol is properly exported / stubbed in all combinations
of CONFIG_NUMA_KEEP_MEMINFO and CONFIG_MEMORY_HOTPLUG.

[[email protected]: v4]
  Link: https://lkml.kernel.org/r/160461461867.1505359.5301571728749534585.stgit@dwillia2-desk3.amr.corp.intel.com
[[email protected]: powerpc: fix create_section_mapping compile warning]
  Link: https://lkml.kernel.org/r/160558386174.2948926.2740149041249041764.stgit@dwillia2-desk3.amr.corp.intel.com

Fixes: a035b6b ("mm/memory_hotplug: introduce default phys_to_target_node() implementation")
Reported-by: Randy Dunlap <[email protected]>
Reported-by: Thomas Gleixner <[email protected]>
Reported-by: kernel test robot <[email protected]>
Reported-by: Christoph Hellwig <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Tested-by: Randy Dunlap <[email protected]>
Tested-by: Thomas Gleixner <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Joao Martins <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Link: https://lkml.kernel.org/r/160447639846.1133764.7044090803980177548.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Linus Torvalds <[email protected]>

arch/ia64/include/asm/sparsemem.h

@@ -18,4 +18,10 @@
 #endif
 
 #endif /* CONFIG_SPARSEMEM */
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+int memory_add_physaddr_to_nid(u64 addr);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
+#endif
+
 #endif /* _ASM_IA64_SPARSEMEM_H */

arch/powerpc/include/asm/mmzone.h

@@ -46,5 +46,10 @@ u64 memory_hotplug_max(void);
 #define __HAVE_ARCH_RESERVED_KERNEL_PAGES
 #endif
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+extern int create_section_mapping(unsigned long start, unsigned long end,
+				  int nid, pgprot_t prot);
+#endif
+
 #endif /* __KERNEL__ */
 #endif /* _ASM_MMZONE_H_ */

arch/powerpc/include/asm/sparsemem.h

@@ -13,9 +13,9 @@
 #endif /* CONFIG_SPARSEMEM */
 
 #ifdef CONFIG_MEMORY_HOTPLUG
-extern int create_section_mapping(unsigned long start, unsigned long end,
-				  int nid, pgprot_t prot);
 extern int remove_section_mapping(unsigned long start, unsigned long end);
+extern int memory_add_physaddr_to_nid(u64 start);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
 
 #ifdef CONFIG_NUMA
 extern int hot_add_scn_to_nid(unsigned long scn_addr);
@@ -26,6 +26,5 @@ static inline int hot_add_scn_to_nid(unsigned long scn_addr)
 }
 #endif /* CONFIG_NUMA */
 #endif /* CONFIG_MEMORY_HOTPLUG */
-
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_SPARSEMEM_H */

arch/powerpc/mm/mem.c

@@ -50,6 +50,7 @@
 #include <asm/rtas.h>
 #include <asm/kasan.h>
 #include <asm/svm.h>
+#include <asm/mmzone.h>
 
 #include <mm/mmu_decl.h>
 

arch/x86/include/asm/sparsemem.h

@@ -28,4 +28,14 @@
 #endif
 
 #endif /* CONFIG_SPARSEMEM */
+
+#ifndef __ASSEMBLY__
+#ifdef CONFIG_NUMA_KEEP_MEMINFO
+extern int phys_to_target_node(phys_addr_t start);
+#define phys_to_target_node phys_to_target_node
+extern int memory_add_physaddr_to_nid(u64 start);
+#define memory_add_physaddr_to_nid memory_add_physaddr_to_nid
+#endif
+#endif /* __ASSEMBLY__ */
+
 #endif /* _ASM_X86_SPARSEMEM_H */

arch/x86/mm/numa.c

@@ -938,6 +938,7 @@ int phys_to_target_node(phys_addr_t start)
 
 	return meminfo_to_nid(&numa_reserved_meminfo, start);
 }
+EXPORT_SYMBOL_GPL(phys_to_target_node);
 
 int memory_add_physaddr_to_nid(u64 start)
 {
@@ -947,4 +948,5 @@ int memory_add_physaddr_to_nid(u64 start)
 		nid = numa_meminfo.blk[0].nid;
 	return nid;
 }
+EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
 #endif

drivers/dax/Kconfig

@@ -50,7 +50,6 @@ config DEV_DAX_HMEM
 	  Say M if unsure.
 
 config DEV_DAX_HMEM_DEVICES
-	depends on NUMA_KEEP_MEMINFO # for phys_to_target_node()
 	depends on DEV_DAX_HMEM && DAX=y
 	def_bool y
 

include/linux/memory_hotplug.h

@@ -281,20 +281,6 @@ static inline bool movable_node_is_enabled(void)
 }
 #endif /* ! CONFIG_MEMORY_HOTPLUG */
 
-#ifdef CONFIG_NUMA
-extern int memory_add_physaddr_to_nid(u64 start);
-extern int phys_to_target_node(u64 start);
-#else
-static inline int memory_add_physaddr_to_nid(u64 start)
-{
-	return 0;
-}
-static inline int phys_to_target_node(u64 start)
-{
-	return 0;
-}
-#endif
-
 #if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT)
 /*
  * pgdat resizing functions

include/linux/numa.h

@@ -21,13 +21,41 @@
 #endif
 
 #ifdef CONFIG_NUMA
+#include <linux/printk.h>
+#include <asm/sparsemem.h>
+
 /* Generic implementation available */
 int numa_map_to_online_node(int node);
-#else
+
+#ifndef memory_add_physaddr_to_nid
+static inline int memory_add_physaddr_to_nid(u64 start)
+{
+	pr_info_once("Unknown online node for memory at 0x%llx, assuming node 0\n",
+			start);
+	return 0;
+}
+#endif
+#ifndef phys_to_target_node
+static inline int phys_to_target_node(u64 start)
+{
+	pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
+			start);
+	return 0;
+}
+#endif
+#else /* !CONFIG_NUMA */
 static inline int numa_map_to_online_node(int node)
 {
 	return NUMA_NO_NODE;
 }
+static inline int memory_add_physaddr_to_nid(u64 start)
+{
+	return 0;
+}
+static inline int phys_to_target_node(u64 start)
+{
+	return 0;
+}
 #endif
 
 #endif /* _LINUX_NUMA_H */

mm/memory_hotplug.c

@@ -350,24 +350,6 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
 	return err;
 }
 
-#ifdef CONFIG_NUMA
-int __weak memory_add_physaddr_to_nid(u64 start)
-{
-	pr_info_once("Unknown online node for memory at 0x%llx, assuming node 0\n",
-			start);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
-
-int __weak phys_to_target_node(u64 start)
-{
-	pr_info_once("Unknown target node for memory at 0x%llx, assuming node 0\n",
-			start);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(phys_to_target_node);
-#endif
-
 /* find the smallest valid pfn in the range [start_pfn, end_pfn) */
 static unsigned long find_smallest_section_pfn(int nid, struct zone *zone,
 				     unsigned long start_pfn,