VFS hot tracking: add one ioctl interface

  FS_IOC_GET_HEAT_INFO: return a struct containing the various
metrics collected in hot_freq_data structs, and also return a
calculated data temperature based on those metrics. Optionally,
retrieve the temperature from the hot data hash list instead of
recalculating it.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
VFS hot tracking, procfs: add one proc interface

  Add one proc interface hot-update-interval under the dir
/proc/sys/fs/ in order to turn HOT_UPDATE_INTERVAL into be tunable.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
VFS hot tracking: add memory caping function

  Introduce two proc interfaces hot-mem-high-thresh and
hot-mem-low-thresh to cap the memory which is consumed by
hot_inode_item and hot_range_item, and they will be in
the unit of 1M bytes.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
VFS hot tracking, btrfs: add hot tracking support

  Introduce one new mount option '-o hot_track',
and add its parsing support.
  Its usage looks like:
   mount -o hot_track
   mount -o nouser,hot_track
   mount -o nouser,hot_track,loop
   mount -o hot_track,nouser

Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
VFS hot tracking: add documentation

      Add Documentation for VFS hot tracking feature

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
VFS hot tracking: add fs hot type support

  Introduce one ability to enable that specific FS
can register its own hot tracking functions.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>