blk-cgroup: config options re-arrangement

This patch fixes few usability and configurability issues.

o All the cgroup based controller options are configurable from
  "Genral Setup/Control Group Support/" menu. blkio is the only exception.
  Hence make this option visible in above menu and make it configurable from
  there to bring it inline with rest of the cgroup based controllers.

o Get rid of CONFIG_DEBUG_CFQ_IOSCHED.

  This option currently does two things.

  - Enable printing of cgroup paths in blktrace
  - Enables CONFIG_DEBUG_BLK_CGROUP, which in turn displays additional stat
    files in cgroup.

  If we are using group scheduling, blktrace data is of not really much use
  if cgroup information is not present. To get this data, currently one has to
  also enable CONFIG_DEBUG_CFQ_IOSCHED, which in turn brings the overhead of
  all the additional debug stat files which is not desired.

  Hence, this patch moves printing of cgroup paths under
  CONFIG_CFQ_GROUP_IOSCHED.

  This allows us to get rid of CONFIG_DEBUG_CFQ_IOSCHED completely. Now all
  the debug stat files are controlled only by CONFIG_DEBUG_BLK_CGROUP which
  can be enabled through config menu.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Divyesh Shah <dpshah@google.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

Documentation/cgroups/blkio-controller.txt

@@ -17,6 +17,9 @@ HOWTO
 You can do a very simple testing of running two dd threads in two different
 cgroups. Here is what you can do.
 
+- Enable Block IO controller
+	CONFIG_BLK_CGROUP=y
+
 - Enable group scheduling in CFQ
 	CONFIG_CFQ_GROUP_IOSCHED=y
 
@@ -54,25 +57,17 @@ cgroups. Here is what you can do.
 
 Various user visible config options
 ===================================
+CONFIG_BLK_CGROUP
+	- Block IO controller.
+
+CONFIG_DEBUG_BLK_CGROUP
+	- Debug help. Right now some additional stats file show up in cgroup
+	  if this option is enabled.
+
 CONFIG_CFQ_GROUP_IOSCHED
 	- Enables group scheduling in CFQ. Currently only 1 level of group
 	  creation is allowed.
 
-CONFIG_DEBUG_CFQ_IOSCHED
-	- Enables some debugging messages in blktrace. Also creates extra
-	  cgroup file blkio.dequeue.
-
-Config options selected automatically
-=====================================
-These config options are not user visible and are selected/deselected
-automatically based on IO scheduler configuration.
-
-CONFIG_BLK_CGROUP
-	- Block IO controller. Selected by CONFIG_CFQ_GROUP_IOSCHED.
-
-CONFIG_DEBUG_BLK_CGROUP
-	- Debug help. Selected by CONFIG_DEBUG_CFQ_IOSCHED.
-
 Details of cgroup files
 =======================
 - blkio.weight
@@ -174,13 +169,13 @@ Details of cgroup files
 	  write, sync or async.
 
 - blkio.avg_queue_size
-	- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y.
+	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
 	  The average queue size for this cgroup over the entire time of this
 	  cgroup's existence. Queue size samples are taken each time one of the
 	  queues of this cgroup gets a timeslice.
 
 - blkio.group_wait_time
-	- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y.
+	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
 	  This is the amount of time the cgroup had to wait since it became busy
 	  (i.e., went from 0 to 1 request queued) to get a timeslice for one of
 	  its queues. This is different from the io_wait_time which is the
@@ -191,7 +186,7 @@ Details of cgroup files
 	  got a timeslice and will not include the current delta.
 
 - blkio.empty_time
-	- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y.
+	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
 	  This is the amount of time a cgroup spends without any pending
 	  requests when not being served, i.e., it does not include any time
 	  spent idling for one of the queues of the cgroup. This is in
@@ -200,7 +195,7 @@ Details of cgroup files
 	  time it had a pending request and will not include the current delta.
 
 - blkio.idle_time
-	- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y.
+	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y.
 	  This is the amount of time spent by the IO scheduler idling for a
 	  given cgroup in anticipation of a better request than the exising ones
 	  from other queues/cgroups. This is in nanoseconds. If this is read
@@ -209,7 +204,7 @@ Details of cgroup files
 	  the current delta.
 
 - blkio.dequeue
-	- Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
+	- Debugging aid only enabled if CONFIG_DEBUG_BLK_CGROUP=y. This
 	  gives the statistics about how many a times a group was dequeued
 	  from service tree of the device. First two fields specify the major
 	  and minor number of the device and third field specifies the number