commit 42dad7647aec49b3ad20dd0cb832b232a6ae514f
author Jerome Marchand <jmarchan@redhat.com> Wed Apr 22 14:01:49 2009 +0200
committer Jens Axboe <jens.axboe@oracle.com> Fri Apr 24 08:54:21 2009 +0200
tree b70d4cb7706f2647e65426e24f078ddf14d6e139
parent 097102c2d04974bdfcfa16a5f3062d499842139c

block: simplify I/O stat accounting

This simplifies I/O stat accounting switching code and separates it
completely from I/O scheduler switch code.

Requests are accounted according to the state of their request queue
at the time of the request allocation. There is no need anymore to
flush the request queue when switching I/O accounting state.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blk-core.c

diff --git a/block/blk-core.c b/block/blk-core.c
index 07ab754..2998fe3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -643,7 +643,7 @@
 }
 
 static struct request *
-blk_alloc_request(struct request_queue *q, int rw, int priv, gfp_t gfp_mask)
+blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
 {
 	struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 
@@ -652,7 +652,7 @@
 
 	blk_rq_init(q, rq);
 
-	rq->cmd_flags = rw | REQ_ALLOCED;
+	rq->cmd_flags = flags | REQ_ALLOCED;
 
 	if (priv) {
 		if (unlikely(elv_set_request(q, rq, gfp_mask))) {
@@ -792,6 +792,8 @@
 	if (priv)
 		rl->elvpriv++;
 
+	if (blk_queue_io_stat(q))
+		rw_flags |= REQ_IO_STAT;
 	spin_unlock_irq(q->queue_lock);
 
 	rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);

block/blk-merge.c

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 63760ca..23d2a6f 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -402,7 +402,10 @@
 
 	elv_merge_requests(q, req, next);
 
-	blk_account_io_merge(req);
+	/*
+	 * 'next' is going away, so update stats accordingly
+	 */
+	blk_account_io_merge(next);
 
 	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
 	if (blk_rq_cpu_valid(next))

block/blk-sysfs.c

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index cac4e9f..3ff9bba 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -209,14 +209,10 @@
 	ssize_t ret = queue_var_store(&stats, page, count);
 
 	spin_lock_irq(q->queue_lock);
-	elv_quiesce_start(q);
-
 	if (stats)
 		queue_flag_set(QUEUE_FLAG_IO_STAT, q);
 	else
 		queue_flag_clear(QUEUE_FLAG_IO_STAT, q);
-
-	elv_quiesce_end(q);
 	spin_unlock_irq(q->queue_lock);
 
 	return ret;

block/blk.h

diff --git a/block/blk.h b/block/blk.h
index 5dfc412..79c85f7 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -114,12 +114,7 @@
 
 static inline int blk_do_io_stat(struct request *rq)
 {
-	struct gendisk *disk = rq->rq_disk;
-
-	if (!disk || !disk->queue)
-		return 0;
-
-	return blk_queue_io_stat(disk->queue) && (rq->cmd_flags & REQ_ELVPRIV);
+	return rq->rq_disk && blk_rq_io_stat(rq);
 }
 
 #endif