[Ocfs2-tools-devel] [PATCH 0/7] Add "sparse" feature change in tunefs.ocfs2, take 2

[Tao Ma]

Change from V1 to V2:
1. Many minor changes have been made, so they are explained seperately
   in the seperated patches.
2. Two more patches have been added. They are:
   1) Move io_cache into main tunefs.c, so that all the operations in
      tunefs can benefit from it.
   2) Add judgement in remove slot, so that it can't coexist with
      "sparse" functions.

The disk layout for ocfs2 volume will be changed for sparse files in 1.4,
so for some boxes which have ocfs2-1.2.* installed, it is impossible for
them to access the new-formatted devices. On the other hand, for some
old-formatted volume, we could turn on this feature so that the future
cluster allocation can use it to save space.

Another new usage for tunefs.ocfs2 is to list all the sparse files in a
volume. This is useful before a user want to disable "sparse_files".
It will provide the user a quick way to list all such files. So he might
just decide that some files are not worth it, like coredumps. And he may
choose to remove them to save spaces.

So add "--list-sparse" "--fs-features=[no]sparse" to tunefs.ocfs2, so
that user can use them to do the feature modification work.
tunfs.ocfs2 now also have to parse the feature-strings,
so move the feature string parsing out of mkfs.ocfs2 and create
a new file named feature_string.c in libocfs2 to handle this work.
Now tunefs.ocfs2 can also use it.