MIPS: Move pgd_alloc() out of header

pgd_alloc() references init_mm which is not exported to modules. In
order for KVM to be able to use pgd_alloc() to allocate GVA page tables,
move pgd_alloc() into a new pgtable.c file and export it to modules.

Signed-off-by: James Hogan <[e-mail]>
Acked-by: Ralf Baechle <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Cc: "Radim Krčmář" <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

arch/mips/include/asm/pgalloc.h

···
  * Initialize a new pgd / pmd table with invalid pointers.
  */
 extern void pgd_init(unsigned long page);
-
-static inline pgd_t *pgd_alloc(struct mm_struct *mm)
-{
-	pgd_t *ret, *init;
-
-	ret = (pgd_t *) __get_free_pages(GFP_KERNEL, PGD_ORDER);
-	if (ret) {
-		init = pgd_offset(&init_mm, 0UL);
-		pgd_init((unsigned long)ret);
-		memcpy(ret + USER_PTRS_PER_PGD, init + USER_PTRS_PER_PGD,
-		       (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
-	}
-
-	return ret;
-}
+extern pgd_t *pgd_alloc(struct mm_struct *mm);
 
 static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 {

arch/mips/mm/Makefile

···
 
 obj-y				+= cache.o dma-default.o extable.o fault.o \
 				   gup.o init.o mmap.o page.o page-funcs.o \
-				   tlbex.o tlbex-fault.o tlb-funcs.o
+				   pgtable.o tlbex.o tlbex-fault.o tlb-funcs.o
 
 ifdef CONFIG_CPU_MICROMIPS
 obj-y				+= uasm-micromips.o

arch/mips/mm/pgtable.c

···
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <asm/pgalloc.h>
+
+pgd_t *pgd_alloc(struct mm_struct *mm)
+{
+	pgd_t *ret, *init;
+
+	ret = (pgd_t *) __get_free_pages(GFP_KERNEL, PGD_ORDER);
+	if (ret) {
+		init = pgd_offset(&init_mm, 0UL);
+		pgd_init((unsigned long)ret);
+		memcpy(ret + USER_PTRS_PER_PGD, init + USER_PTRS_PER_PGD,
+		       (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pgd_alloc);