Merge branch 'for-4.3/blkcg' of git://git.kernel.dk/linux-block

Pull blk-cg updates from Jens Axboe:
 "A bit later in the cycle, but this has been in the block tree for a a
  while.  This is basically four patchsets from Tejun, that improve our
  buffered cgroup writeback.  It was dependent on the other cgroup
  changes, but they went in earlier in this cycle.

  Series 1 is set of 5 patches that has cgroup writeback updates:

   - bdi_writeback iteration fix which could lead to some wb's being
     skipped or repeated during e.g. sync under memory pressure.

   - Simplification of wb work wait mechanism.

   - Writeback tracepoints updated to report cgroup.

  Series 2 is is a set of updates for the CFQ cgroup writeback handling:

     cfq has always charged all async IOs to the root cgroup.  It didn't
     have much choice as writeback didn't know about cgroups and there
     was no way to tell who to blame for a given writeback IO.
     writeback finally grew support for cgroups and now tags each
     writeback IO with the appropriate cgroup to charge it against.

     This patchset updates cfq so that it follows the blkcg each bio is
     tagged with.  Async cfq_queues are now shared across cfq_group,
     which is per-cgroup, instead of per-request_queue cfq_data.  This
     makes all IOs follow the weight based IO resource distribution
     implemented by cfq.

     - Switched from GFP_ATOMIC to GFP_NOWAIT as suggested by Jeff.

     - Other misc review points addressed, acks added and rebased.

  Series 3 is the blkcg policy cleanup patches:

     This patchset contains assorted cleanups for blkcg_policy methods
     and blk[c]g_policy_data handling.

     - alloc/free added for blkg_policy_data.  exit dropped.

     - alloc/free added for blkcg_policy_data.

     - blk-throttle's async percpu allocation is replaced with direct
       allocation.

     - all methods now take blk[c]g_policy_data instead of blkcg_gq or
       blkcg.

  And finally, series 4 is a set of patches cleaning up the blkcg stats
  handling:

    blkcg's stats have always been somwhat of a mess.  This patchset
    tries to improve the situation a bit.

     - The following patches added to consolidate blkcg entry point and
       blkg creation.  This is in itself is an improvement and helps
       colllecting common stats on bio issue.

     - per-blkg stats now accounted on bio issue rather than request
       completion so that bio based and request based drivers can behave
       the same way.  The issue was spotted by Vivek.

     - cfq-iosched implements custom recursive stats and blk-throttle
       implements custom per-cpu stats.  This patchset make blkcg core
       support both by default.

     - cfq-iosched and blk-throttle keep track of the same stats
       multiple times.  Unify them"

* 'for-4.3/blkcg' of git://git.kernel.dk/linux-block: (45 commits)
  blkcg: use CGROUP_WEIGHT_* scale for io.weight on the unified hierarchy
  blkcg: s/CFQ_WEIGHT_*/CFQ_WEIGHT_LEGACY_*/
  blkcg: implement interface for the unified hierarchy
  blkcg: misc preparations for unified hierarchy interface
  blkcg: separate out tg_conf_updated() from tg_set_conf()
  blkcg: move body parsing from blkg_conf_prep() to its callers
  blkcg: mark existing cftypes as legacy
  blkcg: rename subsystem name from blkio to io
  blkcg: refine error codes returned during blkcg configuration
  blkcg: remove unnecessary NULL checks from __cfqg_set_weight_device()
  blkcg: reduce stack usage of blkg_rwstat_recursive_sum()
  blkcg: remove cfqg_stats->sectors
  blkcg: move io_service_bytes and io_serviced stats into blkcg_gq
  blkcg: make blkg_[rw]stat_recursive_sum() to be able to index into blkcg_gq
  blkcg: make blkcg_[rw]stat per-cpu
  blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead_stats with it
  blkcg: consolidate blkg creation in blkcg_bio_issue_check()
  blk-throttle: improve queue bypass handling
  blkcg: move root blkg lookup optimization from throtl_lookup_tg() to __blkg_lookup()
  blkcg: inline [__]blkg_lookup()
  ...

2 files changed, 63 insertions, 22 deletions

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index 68b6a6a470b0..12686bec37b9 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -201,7 +201,7 @@ Proportional weight policy files
 	  specifies the number of bytes.
 
 - blkio.io_serviced
-	- Number of IOs completed to/from the disk by the group. These
+	- Number of IOs (bio) issued to the disk by the group. These
 	  are further divided by the type of operation - read or write, sync
 	  or async. First two fields specify the major and minor number of the
 	  device, third field specifies the operation type and the fourth field
@@ -327,18 +327,11 @@ Note: If both BW and IOPS rules are specified for a device, then IO is
       subjected to both the constraints.
 
 - blkio.throttle.io_serviced
-	- Number of IOs (bio) completed to/from the disk by the group (as
-	  seen by throttling policy). These are further divided by the type
-	  of operation - read or write, sync or async. First two fields specify
-	  the major and minor number of the device, third field specifies the
-	  operation type and the fourth field specifies the number of IOs.
-
-	  blkio.io_serviced does accounting as seen by CFQ and counts are in
-	  number of requests (struct request). On the other hand,
-	  blkio.throttle.io_serviced counts number of IO in terms of number
-	  of bios as seen by throttling policy.  These bios can later be
-	  merged by elevator and total number of requests completed can be
-	  lesser.
+	- Number of IOs (bio) issued to the disk by the group. These
+	  are further divided by the type of operation - read or write, sync
+	  or async. First two fields specify the major and minor number of the
+	  device, third field specifies the operation type and the fourth field
+	  specifies the number of IOs.
 
 - blkio.throttle.io_service_bytes
 	- Number of bytes transferred to/from the disk by the group. These
@@ -347,11 +340,6 @@ Note: If both BW and IOPS rules are specified for a device, then IO is
 	  device, third field specifies the operation type and the fourth field
 	  specifies the number of bytes.
 
-	  These numbers should roughly be same as blkio.io_service_bytes as
-	  updated by CFQ. The difference between two is that
-	  blkio.io_service_bytes will not be updated if CFQ is not operating
-	  on request queue.
-
 Common files among various policies
 -----------------------------------
 - blkio.reset_stats
diff --git a/Documentation/cgroups/unified-hierarchy.txt b/Documentation/cgroups/unified-hierarchy.txt
index 1ee9caf29e57..e0975c2cf03d 100644
--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -27,7 +27,7 @@ CONTENTS
     5-3-1. Format
     5-3-2. Control Knobs
   5-4. Per-Controller Changes
-    5-4-1. blkio
+    5-4-1. io
     5-4-2. cpuset
     5-4-3. memory
 6. Planned Changes
@@ -203,7 +203,7 @@ other issues.  The mapping from nice level to weight isn't obvious or
 universal, and there are various other knobs which simply aren't
 available for tasks.
 
-The blkio controller implicitly creates a hidden leaf node for each
+The io controller implicitly creates a hidden leaf node for each
 cgroup to host the tasks.  The hidden leaf has its own copies of all
 the knobs with "leaf_" prefixed.  While this allows equivalent control
 over internal tasks, it's with serious drawbacks.  It always adds an
@@ -438,9 +438,62 @@ may be specified in any order and not all pairs have to be specified.
 
 5-4. Per-Controller Changes
 
-5-4-1. blkio
+5-4-1. io
 
-- blk-throttle becomes properly hierarchical.
+- blkio is renamed to io.  The interface is overhauled anyway.  The
+  new name is more in line with the other two major controllers, cpu
+  and memory, and better suited given that it may be used for cgroup
+  writeback without involving block layer.
+
+- Everything including stat is always hierarchical making separate
+  recursive stat files pointless and, as no internal node can have
+  tasks, leaf weights are meaningless.  The operation model is
+  simplified and the interface is overhauled accordingly.
+
+  io.stat
+
+	The stat file.  The reported stats are from the point where
+	bio's are issued to request_queue.  The stats are counted
+	independent of which policies are enabled.  Each line in the
+	file follows the following format.  More fields may later be
+	added at the end.
+
+	  $MAJ:$MIN rbytes=$RBYTES wbytes=$WBYTES rios=$RIOS wrios=$WIOS
+
+  io.weight
+
+	The weight setting, currently only available and effective if
+	cfq-iosched is in use for the target device.  The weight is
+	between 1 and 10000 and defaults to 100.  The first line
+	always contains the default weight in the following format to
+	use when per-device setting is missing.
+
+	  default $WEIGHT
+
+	Subsequent lines list per-device weights of the following
+	format.
+
+	  $MAJ:$MIN $WEIGHT
+
+	Writing "$WEIGHT" or "default $WEIGHT" changes the default
+	setting.  Writing "$MAJ:$MIN $WEIGHT" sets per-device weight
+	while "$MAJ:$MIN default" clears it.
+
+	This file is available only on non-root cgroups.
+
+  io.max
+
+	The maximum bandwidth and/or iops setting, only available if
+	blk-throttle is enabled.  The file is of the following format.
+
+	  $MAJ:$MIN rbps=$RBPS wbps=$WBPS riops=$RIOPS wiops=$WIOPS
+
+	${R|W}BPS are read/write bytes per second and ${R|W}IOPS are
+	read/write IOs per second.  "max" indicates no limit.  Writing
+	to the file follows the same format but the individual
+	settings may be ommitted or specified in any order.
+
+	This file is available only on non-root cgroups.
 
 
 5-4-2. cpuset