ocfs2-fix-issue-that-ocfs2_setattr-does-not-deal-with-new_i_size==i_size-v2

ocfs2-fix-issue-that-ocfs2_setattr-does-not-deal-with-new_i_size==i_size-v2

Compared with PATCH V1, bug description is updated, and pointless comments
are removed.

Signed-off-by: Younger Liu <younger.liu@huawei.com>
Cc: Jie Liu <jeff.liu@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Sunil Mushran <sunil.mushran@gmail.com>
Cc: Jensen <shencanquan@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>