Btrfs: add tests for btrfs_get_extent

I'm going to be removing hole extents in the near future so I wanted to make a
sanity test for btrfs_get_extent to make sure I don't break anything in the
meantime.  This patch just puts btrfs_get_extent through its paces by giving it
a completely unreasonable mapping to look at and make sure it is giving us back
maps that make sense.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/tests/btrfs-tests.h b/fs/btrfs/tests/btrfs-tests.h
index e935fe5..b353bc8 100644
--- a/fs/btrfs/tests/btrfs-tests.h
+++ b/fs/btrfs/tests/btrfs-tests.h
@@ -26,6 +26,7 @@
 int btrfs_test_free_space_cache(void);
 int btrfs_test_extent_buffer_operations(void);
 int btrfs_test_extent_io(void);
+int btrfs_test_inodes(void);
 int btrfs_init_test_fs(void);
 void btrfs_destroy_test_fs(void);
 struct inode *btrfs_new_test_inode(void);
@@ -49,6 +50,10 @@
 {
 	return 0;
 }
+static inline int btrfs_test_inodes(void)
+{
+	return 0;
+}
 #endif
 
 #endif