files: Split open_reg_by_id into two parts

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -815,6 +815,11 @@ static int do_open_reg(int ns_root_fd, struct reg_file_info *rfi, void *arg)
 	return fd;
 }
 
+int open_reg_fd(struct file_desc *fd)
+{
+	return open_path(fd, do_open_reg_noseek, NULL);
+}
+
 int open_reg_by_id(u32 id)
 {
 	struct file_desc *fd;
@@ -831,7 +836,7 @@ int open_reg_by_id(u32 id)
 		return -1;
 	}
 
-	return open_path(fd, do_open_reg_noseek, NULL);
+	return open_reg_fd(fd);
 }
 
 int get_filemap_fd(struct vma_area *vma)

include/files-reg.h

@@ -26,6 +26,7 @@ struct reg_file_info {
 };
 
 extern int open_reg_by_id(u32 id);
+extern int open_reg_fd(struct file_desc *);
 extern int open_path(struct file_desc *, int (*open_cb)(int ns_root_fd,
 			struct reg_file_info *, void *), void *arg);
 extern void clear_ghost_files(void);