block, cfq: reorganize cfq_io_context into generic and cfq specific parts

Currently io_context and cfq logics are mixed without clear boundary.
Most of io_context is independent from cfq but cfq_io_context handling
logic is dispersed between generic ioc code and cfq.

cfq_io_context represents association between an io_context and a
request_queue, which is a concept useful outside of cfq, but it also
contains fields which are useful only to cfq.

This patch takes out generic part and put it into io_cq (io
context-queue) and the rest into cfq_io_cq (cic moniker remains the
same) which contains io_cq.  The following changes are made together.

* cfq_ttime and cfq_io_cq now live in cfq-iosched.c.

* All related fields, functions and constants are renamed accordingly.

* ioc->ioc_data is now "struct io_cq *" instead of "void *" and
  renamed to icq_hint.

This prepares for io_context API cleanup.  Documentation is currently
sparse.  It will be added later.

Changes in this patch are mechanical and don't cause functional
change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 14 insertions, 29 deletions

diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index b2b75a54f252..d15ca6591f96 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -5,38 +5,23 @@
 #include <linux/rcupdate.h>
 #include <linux/workqueue.h>
 
-struct cfq_queue;
-struct cfq_ttime {
-        unsigned long last_end_request;
-
-        unsigned long ttime_total;
-        unsigned long ttime_samples;
-        unsigned long ttime_mean;
-};
-
 enum {
-        CIC_IOPRIO_CHANGED,
-        CIC_CGROUP_CHANGED,
+        ICQ_IOPRIO_CHANGED,
+        ICQ_CGROUP_CHANGED,
 };
 
-struct cfq_io_context {
-        struct request_queue *q;
-
-        struct cfq_queue *cfqq[2];
-
-        struct io_context *ioc;
-
-        struct cfq_ttime ttime;
-
-        struct list_head queue_list;
-        struct hlist_node cic_list;
+struct io_cq {
+        struct request_queue    *q;
+        struct io_context       *ioc;
 
-        unsigned long changed;
+        struct list_head        q_node;
+        struct hlist_node       ioc_node;
 
-        void (*exit)(struct cfq_io_context *);
-        void (*release)(struct cfq_io_context *);
+        unsigned long           changed;
+        struct rcu_head         rcu_head;
 
-        struct rcu_head rcu_head;
+        void (*exit)(struct io_cq *);
+        void (*release)(struct io_cq *);
 };
 
 /*
@@ -58,9 +43,9 @@ struct io_context {
         int nr_batch_requests;     /* Number of requests left in the batch */
         unsigned long last_waited; /* Time last woken after wait for request */
 
-        struct radix_tree_root radix_root;
-        struct hlist_head cic_list;
-        void __rcu *ioc_data;
+        struct radix_tree_root  icq_tree;
+        struct io_cq __rcu      *icq_hint;
+        struct hlist_head       icq_list;
 
         struct work_struct release_work;
 };