mm: Expose vmap_pages_range() to the rest of the kernel.

The next commit will introduce bpf_arena which is a sparsely populated shared
memory region between bpf program and user space process.
It will function similar to vmalloc()/vm_map_ram():
- get_vm_area()
- alloc_pages()
- vmap_pages_range()

Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Alexei Starovoitov

include/linux/vmalloc.h

@@ -233,6 +233,8 @@ static inline bool is_vm_area_hugepages(const void *addr)
 
 #ifdef CONFIG_MMU
 void vunmap_range(unsigned long addr, unsigned long end);
+int vmap_pages_range(unsigned long addr, unsigned long end,
+		     pgprot_t prot, struct page **pages, unsigned int page_shift);
 static inline void set_vm_flush_reset_perms(void *addr)
 {
 	struct vm_struct *vm = find_vm_area(addr);

mm/vmalloc.c

@@ -625,8 +625,8 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
  * RETURNS:
  * 0 on success, -errno on failure.
  */
-static int vmap_pages_range(unsigned long addr, unsigned long end,
-		pgprot_t prot, struct page **pages, unsigned int page_shift)
+int vmap_pages_range(unsigned long addr, unsigned long end,
+		     pgprot_t prot, struct page **pages, unsigned int page_shift)
 {
 	int err;