This patch changes noop to use queue scheduling code from elevator layer.
One can go back to old noop by deselecting CONFIG_IOSCHED_NOOP_HIER.

Signed-off-by: Nauman Rafique <nau...@google.com>
Signed-off-by: Vivek Goyal <vgo...@redhat.com>
---
 block/Kconfig.iosched |   11 +++++++++++
 block/noop-iosched.c  |   13 +++++++++++++
 2 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index a91a807..9da6657 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -25,6 +25,17 @@ config IOSCHED_NOOP
          that do their own scheduling and require only minimal assistance from
          the kernel.
 
+config IOSCHED_NOOP_HIER
+       bool "Noop Hierarchical Scheduling support"
+       depends on IOSCHED_NOOP && CGROUPS
+       select ELV_FAIR_QUEUING
+       select GROUP_IOSCHED
+       default n
+       ---help---
+         Enable hierarhical scheduling in noop. In this mode noop keeps
+         one IO queue per cgroup instead of a global queue. Elevator
+         fair queuing logic ensures fairness among various queues.
+
 config IOSCHED_AS
        tristate "Anticipatory I/O scheduler"
        default y
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 731dbf2..97ea41b 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -82,6 +82,15 @@ static void noop_free_noop_queue(struct elevator_queue *e, 
void *sched_queue)
        kfree(nq);
 }
 
+#ifdef CONFIG_IOSCHED_NOOP_HIER
+static struct elv_fs_entry noop_attrs[] = {
+       ELV_ATTR(fairness),
+       ELV_ATTR(slice_idle),
+       ELV_ATTR(slice_sync),
+       __ATTR_NULL
+};
+#endif
+
 static struct elevator_type elevator_noop = {
        .ops = {
                .elevator_merge_req_fn          = noop_merged_requests,
@@ -92,6 +101,10 @@ static struct elevator_type elevator_noop = {
                .elevator_alloc_sched_queue_fn  = noop_alloc_noop_queue,
                .elevator_free_sched_queue_fn   = noop_free_noop_queue,
        },
+#ifdef CONFIG_IOSCHED_NOOP_HIER
+       .elevator_features = ELV_IOSCHED_NEED_FQ | ELV_IOSCHED_SINGLE_IOQ,
+       .elevator_attrs = noop_attrs,
+#endif
        .elevator_name = "noop",
        .elevator_owner = THIS_MODULE,
 };
-- 
1.6.0.6

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