title: ext4 enable hashes for directory entries
body: <p>According to <a href="https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Hash_Tree_Directories" rel="nofollow noreferrer">kernel.org</a> there is the possibility to store dentries in trees instead of lists but you need to enable this flag (EXT4_INDEX_FL) in the inode structure. I this enabled by default or I have to format my partition with some flags?</p>
  
  <p>I need to store lots of small files (same old problem) of about 130k each and I understood that this will help to speed up lookup and also that it is recommended to store those files in a 2 level directories hierarchy. Is there something else I need to consider so that this doesn't blow up if want to store something close to 60.000.000 of this kind of files ? (maybe some other values for block size, number of blocks in a group)</p>