block: share request flush fields with elevator_private

Flush requests are never put on the IO scheduler.  Convert request
structure's elevator_private* into an array and have the flush fields
share a union with it.

Reclaim the space lost in 'struct request' by moving 'completion_data'
back in the union with 'rb_node'.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4cd59b0..968455c 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -54,9 +54,9 @@ static const int cfq_hist_divisor = 4;
 #define CFQQ_SEEKY(cfqq)       (hweight32(cfqq->seek_history) > 32/8)
 
 #define RQ_CIC(rq)             \
-       ((struct cfq_io_context *) (rq)->elevator_private)
-#define RQ_CFQQ(rq)            (struct cfq_queue *) ((rq)->elevator_private2)
-#define RQ_CFQG(rq)            (struct cfq_group *) ((rq)->elevator_private3)
+       ((struct cfq_io_context *) (rq)->elevator_private[0])
+#define RQ_CFQQ(rq)            (struct cfq_queue *) ((rq)->elevator_private[1])
+#define RQ_CFQG(rq)            (struct cfq_group *) ((rq)->elevator_private[2])
 
 static struct kmem_cache *cfq_pool;
 static struct kmem_cache *cfq_ioc_pool;
@@ -3589,12 +3589,12 @@ static void cfq_put_request(struct request *rq)
 
                put_io_context(RQ_CIC(rq)->ioc);
 
-               rq->elevator_private = NULL;
-               rq->elevator_private2 = NULL;
+               rq->elevator_private[0] = NULL;
+               rq->elevator_private[1] = NULL;
 
                /* Put down rq reference on cfqg */
                cfq_put_cfqg(RQ_CFQG(rq));
-               rq->elevator_private3 = NULL;
+               rq->elevator_private[2] = NULL;
 
                cfq_put_queue(cfqq);
        }
@@ -3685,9 +3685,9 @@ new_queue:
 
        spin_unlock_irqrestore(q->queue_lock, flags);
 
-       rq->elevator_private = cic;
-       rq->elevator_private2 = cfqq;
-       rq->elevator_private3 = cfq_ref_get_cfqg(cfqq->cfqg);
+       rq->elevator_private[0] = cic;
+       rq->elevator_private[1] = cfqq;
+       rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
        return 0;
 
 queue_fail:

diff --git a/block/elevator.c b/block/elevator.c
index 270e097..f98e92e 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -764,7 +764,7 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
        if (e->ops->elevator_set_req_fn)
                return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
 
-       rq->elevator_private = NULL;
+       rq->elevator_private[0] = NULL;
        return 0;
 }
 

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 6d7e9af..12bb426 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -99,25 +99,26 @@ struct request {
        /*
         * The rb_node is only used inside the io scheduler, requests
         * are pruned when moved to the dispatch queue. So let the
-        * flush fields share space with the rb_node.
+        * completion_data share space with the rb_node.
         */
        union {
                struct rb_node rb_node; /* sort/lookup */
-               struct {
-                       unsigned int                    seq;
-                       struct list_head                list;
-               } flush;
+               void *completion_data;
        };
 
-       void *completion_data;
-
        /*
         * Three pointers are available for the IO schedulers, if they need
-        * more they have to dynamically allocate it.
+        * more they have to dynamically allocate it.  Flush requests are
+        * never put on the IO scheduler. So let the flush fields share
+        * space with the three elevator_private pointers.
         */
-       void *elevator_private;
-       void *elevator_private2;
-       void *elevator_private3;
+       union {
+               void *elevator_private[3];
+               struct {
+                       unsigned int            seq;
+                       struct list_head        list;
+               } flush;
+       };
 
        struct gendisk *rq_disk;
        unsigned long start_time;