mm: memory: make numa_migrate_prep() non-static

The numa_migrate_prep() will be used by huge NUMA fault as well in the
following patch, make it non-static.

Link: https://lkml.kernel.org/r/20210518200801.7413-3-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/internal.h

@@ -672,4 +672,7 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
 
 void vunmap_range_noflush(unsigned long start, unsigned long end);
 
+int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
+		      unsigned long addr, int page_nid, int *flags);
+
 #endif	/* __MM_INTERNAL_H */

mm/memory.c

@@ -4175,9 +4175,8 @@ static vm_fault_t do_fault(struct vm_fault *vmf)
 	return ret;
 }
 
-static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
-				unsigned long addr, int page_nid,
-				int *flags)
+int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
+		      unsigned long addr, int page_nid, int *flags)
 {
 	get_page(page);