blk-cgroup: Initialize ioc->cgroup_changed at ioc creation time

If we don't explicitly initialize it to zero, CFQ might think that
cgroup of ioc has changed and it generates lots of unnecessary calls
to call_for_each_cic(changed_cgroup). Fix it.

cfq_get_io_context()
  cfq_ioc_set_cgroup()
     call_for_each_cic(ioc, changed_cgroup)

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index b791022beef3..c898049dafd5 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -96,6 +96,9 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
                 INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
                 INIT_HLIST_HEAD(&ret->cic_list);
                 ret->ioc_data = NULL;
+#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
+                ret->cgroup_changed = 0;
+#endif
         }
 
         return ret;