Merge branch 'for-3.11/core' of git://git.kernel.dk/linux-block

Pull core block IO updates from Jens Axboe:
 "Here are the core IO block bits for 3.11. It contains:

   - A tweak to the reserved tag logic from Jan, for weirdo devices with
     just 3 free tags.  But for those it improves things substantially
     for random writes.

   - Periodic writeback fix from Jan.  Marked for stable as well.

   - Fix for a race condition in IO scheduler switching from Jianpeng.

   - The hierarchical blk-cgroup support from Tejun.  This is the grunt
     of the series.

   - blk-throttle fix from Vivek.

  Just a note that I'm in the middle of a relocation, whole family is
  flying out tomorrow.  Hence I will be awal the remainder of this week,
  but back at work again on Monday the 15th.  CC'ing Tejun, since any
  potential "surprises" will most likely be from the blk-cgroup work.
  But it's been brewing for a while and sitting in my tree and
  linux-next for a long time, so should be solid."

* 'for-3.11/core' of git://git.kernel.dk/linux-block: (36 commits)
  elevator: Fix a race in elevator switching
  block: Reserve only one queue tag for sync IO if only 3 tags are available
  writeback: Fix periodic writeback after fs mount
  blk-throttle: implement proper hierarchy support
  blk-throttle: implement throtl_grp->has_rules[]
  blk-throttle: Account for child group's start time in parent while bio climbs up
  blk-throttle: add throtl_qnode for dispatch fairness
  blk-throttle: make throtl_pending_timer_fn() ready for hierarchy
  blk-throttle: make tg_dispatch_one_bio() ready for hierarchy
  blk-throttle: make blk_throtl_bio() ready for hierarchy
  blk-throttle: make blk_throtl_drain() ready for hierarchy
  blk-throttle: dispatch from throtl_pending_timer_fn()
  blk-throttle: implement dispatch looping
  blk-throttle: separate out throtl_service_queue->pending_timer from throtl_data->dispatch_work
  blk-throttle: set REQ_THROTTLED from throtl_charge_bio() and gate stats update with it
  blk-throttle: implement sq_to_tg(), sq_to_td() and throtl_log()
  blk-throttle: add throtl_service_queue->parent_sq
  blk-throttle: generalize update_disptime optimization in blk_throtl_bio()
  blk-throttle: dispatch to throtl_data->service_queue.bio_lists[]
  blk-throttle: move bio_lists[] and friends to throtl_service_queue
  ...

1 files changed, 15 insertions, 14 deletions

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index da272c8f44e7..cd556b914786 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -94,11 +94,13 @@ Throttling/Upper Limit policy
 
 Hierarchical Cgroups
 ====================
-- Currently only CFQ supports hierarchical groups. For throttling,
-  cgroup interface does allow creation of hierarchical cgroups and
-  internally it treats them as flat hierarchy.
 
-  If somebody created a hierarchy like as follows.
+Both CFQ and throttling implement hierarchy support; however,
+throttling's hierarchy support is enabled iff "sane_behavior" is
+enabled from cgroup side, which currently is a development option and
+not publicly available.
+
+If somebody created a hierarchy like as follows.
 
                         root
                         /  \
@@ -106,21 +108,20 @@ Hierarchical Cgroups
                         |
                      test3
 
-  CFQ will handle the hierarchy correctly but and throttling will
-  practically treat all groups at same level. For details on CFQ
-  hierarchy support, refer to Documentation/block/cfq-iosched.txt.
-  Throttling will treat the hierarchy as if it looks like the
-  following.
+CFQ by default and throttling with "sane_behavior" will handle the
+hierarchy correctly.  For details on CFQ hierarchy support, refer to
+Documentation/block/cfq-iosched.txt.  For throttling, all limits apply
+to the whole subtree while all statistics are local to the IOs
+directly generated by tasks in that cgroup.
+
+Throttling without "sane_behavior" enabled from cgroup side will
+practically treat all groups at same level as if it looks like the
+following.
 
                                 pivot
                              /  /   \  \
                         root  test1 test2  test3
 
-  Nesting cgroups, while allowed, isn't officially supported and blkio
-  genereates warning when cgroups nest. Once throttling implements
-  hierarchy support, hierarchy will be supported and the warning will
-  be removed.
-
 Various user visible config options
 ===================================
 CONFIG_BLK_CGROUP