- stat-prefetch aims to optimize operations like 'ls -l' where a readdir
   is immediately followed by stat calls on each of the directory entry read.
   More details on design can be found in doc/stat-prefetch-design.txt

Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 221 (stat prefetch implementation)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=221

lookup can fetch the entire file in xattr dictionary using the key
"glusterfs.content". We set the maximum size of the file that can
be fetched so in the xattr_req dictionary using the same key. If file-size
is less than or equal to the value set in dictionary, the content is stored
in the dictionary using same key in lookup_cbk.

For small files, we can do an optimization wherein we do not really send the
calls open, read and close to the storage translators. Instead there can be
an xlator which fakes open, read and close calls. For reads, it sends the data
it has cached during lookup and hence saving the time for open, read and close
calls to reach storage translators (this time can be significant if calls have
to go through network to reach storage translator).

Signed-off-by: Anand V. Avati <avati@dev.gluster.com>