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;
 };