mke2fs: require the bigalloc feature explicity if the cluster size is set

When cluster-size is specified without the bigalloc feature, mke2fs
will ignore this argument silently.  But user might think bigalloc
feature has been enabled unless they use the dumpe2fs command.  So now
we ask user to set bigalloc feature explicity when cluster-size is
enabled.  This can make sure that users understand what they are doing
because bigalloc might impact the performance for some workloads.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 32b4c34e50931199364b36004459c72ef9e2b472..4748f4ab6ae725c7ca154eafd948fe75470ef51a 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1847,6 +1847,11 @@ profile_error:
                                                            blocksize*16);
                fs_param.s_log_cluster_size =
                        int_log2(cluster_size >> EXT2_MIN_CLUSTER_LOG_SIZE);
+       } else if (cluster_size) {
+               com_err(program_name, 0,
+                       _("specifying a cluster size requires the "
+                         "bigalloc feature"));
+               exit(1);
        } else
                fs_param.s_log_cluster_size = fs_param.s_log_block_size;