7 files changed, 55 insertions, 64 deletions

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index d422b410a995..48e0b21b0059 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/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
 
@@ -54,24 +57,16 @@ cgroups. Here is what you can do.
 
 Various user visible config options
 ===================================
-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.
+        - Block IO controller.
 
 CONFIG_DEBUG_BLK_CGROUP
-        - Debug help. Selected by CONFIG_DEBUG_CFQ_IOSCHED.
+        - 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.
 
 Details of cgroup files
 =======================
@@ -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
diff --git a/block/Kconfig b/block/Kconfig
index f9e89f4d94bb..9be0b56eaee1 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -77,29 +77,6 @@ config BLK_DEV_INTEGRITY
         T10/SCSI Data Integrity Field or the T13/ATA External Path
         Protection.  If in doubt, say N.
 
-config BLK_CGROUP
-        tristate "Block cgroup support"
-        depends on CGROUPS
-        depends on CFQ_GROUP_IOSCHED
-        default n
-        ---help---
-        Generic block IO controller cgroup interface. This is the common
-        cgroup interface which should be used by various IO controlling
-        policies.
-
-        Currently, CFQ IO scheduler uses it to recognize task groups and
-        control disk bandwidth allocation (proportional time slice allocation)
-        to such task groups.
-
-config DEBUG_BLK_CGROUP
-        bool
-        depends on BLK_CGROUP
-        default n
-        ---help---
-        Enable some debugging help. Currently it stores the cgroup path
-        in the blk group which can be used by cfq for tracing various
-        group related activity.
-
 endif # BLOCK
 
 config BLOCK_COMPAT
diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index fc71cf071fb2..3199b76f795d 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -23,7 +23,8 @@ config IOSCHED_DEADLINE
 
 config IOSCHED_CFQ
         tristate "CFQ I/O scheduler"
-        select BLK_CGROUP if CFQ_GROUP_IOSCHED
+        # If BLK_CGROUP is a module, CFQ has to be built as module.
+        depends on (BLK_CGROUP=m && m) || !BLK_CGROUP || BLK_CGROUP=y
         default y
         ---help---
           The CFQ I/O scheduler tries to distribute bandwidth equally
@@ -33,22 +34,15 @@ config IOSCHED_CFQ
 
           This is the default I/O scheduler.
 
+          Note: If BLK_CGROUP=m, then CFQ can be built only as module.
+
 config CFQ_GROUP_IOSCHED
         bool "CFQ Group Scheduling support"
-        depends on IOSCHED_CFQ && CGROUPS
+        depends on IOSCHED_CFQ && BLK_CGROUP
         default n
         ---help---
           Enable group IO scheduling in CFQ.
 
-config DEBUG_CFQ_IOSCHED
-        bool "Debug CFQ Scheduling"
-        depends on CFQ_GROUP_IOSCHED
-        select DEBUG_BLK_CGROUP
-        default n
-        ---help---
-          Enable CFQ IO scheduling debugging in CFQ. Currently it makes
-          blktrace output more verbose.
-
 choice
         prompt "Default I/O scheduler"
         default DEFAULT_CFQ
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index af42efbb0c1d..d02bbf88de13 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -351,10 +351,8 @@ void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
         blkg->blkcg_id = css_id(&blkcg->css);
         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
         spin_unlock_irqrestore(&blkcg->lock, flags);
-#ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Need to take css reference ? */
         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
-#endif
         blkg->dev = dev;
 }
 EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index a491a6d56ecf..2b866ec1dcea 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -108,10 +108,8 @@ struct blkio_group {
         void *key;
         struct hlist_node blkcg_node;
         unsigned short blkcg_id;
-#ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Store cgroup path */
         char path[128];
-#endif
         /* The device MKDEV(major, minor), this group has been created for */
         dev_t dev;
 
@@ -147,6 +145,11 @@ struct blkio_policy_type {
 extern void blkio_policy_register(struct blkio_policy_type *);
 extern void blkio_policy_unregister(struct blkio_policy_type *);
 
+static inline char *blkg_path(struct blkio_group *blkg)
+{
+        return blkg->path;
+}
+
 #else
 
 struct blkio_group {
@@ -158,6 +161,8 @@ struct blkio_policy_type {
 static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { }
 static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
 
+static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
+
 #endif
 
 #define BLKIO_WEIGHT_MIN        100
@@ -165,10 +170,6 @@ static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { }
 #define BLKIO_WEIGHT_DEFAULT    500
 
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-static inline char *blkg_path(struct blkio_group *blkg)
-{
-        return blkg->path;
-}
 void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg);
 void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
                                 unsigned long dequeue);
@@ -197,7 +198,6 @@ BLKG_FLAG_FNS(idling)
 BLKG_FLAG_FNS(empty)
 #undef BLKG_FLAG_FNS
 #else
-static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
 static inline void blkiocg_update_avg_queue_size_stats(
                                                 struct blkio_group *blkg) {}
 static inline void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 002a5b621653..286008cf889e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -345,7 +345,7 @@ CFQ_CFQQ_FNS(deep);
 CFQ_CFQQ_FNS(wait_busy);
 #undef CFQ_CFQQ_FNS
 
-#ifdef CONFIG_DEBUG_CFQ_IOSCHED
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
         blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
                         cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
diff --git a/init/Kconfig b/init/Kconfig
index eb77e8ccde1c..087c14f3c595 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -612,6 +612,33 @@ config RT_GROUP_SCHED
 
 endif #CGROUP_SCHED
 
+config BLK_CGROUP
+        tristate "Block IO controller"
+        depends on CGROUPS && BLOCK
+        default n
+        ---help---
+        Generic block IO controller cgroup interface. This is the common
+        cgroup interface which should be used by various IO controlling
+        policies.
+
+        Currently, CFQ IO scheduler uses it to recognize task groups and
+        control disk bandwidth allocation (proportional time slice allocation)
+        to such task groups.
+
+        This option only enables generic Block IO controller infrastructure.
+        One needs to also enable actual IO controlling logic in CFQ for it
+        to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
+
+        See Documentation/cgroups/blkio-controller.txt for more information.
+
+config DEBUG_BLK_CGROUP
+        bool "Enable Block IO controller debugging"
+        depends on BLK_CGROUP
+        default n
+        ---help---
+        Enable some debugging help. Currently it exports additional stat
+        files in a cgroup which can be useful for debugging.
+
 endif # CGROUPS
 
 config MM_OWNER