Btrfs: self-tests: Fix test_bitmaps fail on 64k sectorsize

With 64K sectorsize, 1G sized block group cannot span across bitmaps.
To execute test_bitmaps() function, this commit allocates
"BITS_PER_BITMAP * sectorsize + PAGE_SIZE" sized block group.
Reviewed-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Feifei Xu <xufeifei@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/tests/free-space-tests.c

@@ -843,7 +843,13 @@ int btrfs_test_free_space_cache(u32 sectorsize, u32 nodesize)
 
 	test_msg("Running btrfs free space cache tests\n");
 
-	cache = btrfs_alloc_dummy_block_group(1024 * 1024 * 1024, sectorsize);
+	/*
+	 * For ppc64 (with 64k page size), bytes per bitmap might be
+	 * larger than 1G.  To make bitmap test available in ppc64,
+	 * alloc dummy block group whose size cross bitmaps.
+	 */
+	cache = btrfs_alloc_dummy_block_group(BITS_PER_BITMAP * sectorsize
+					+ PAGE_SIZE, sectorsize);
 	if (!cache) {
 		test_msg("Couldn't run the tests\n");
 		return 0;