block: fix inconsistency in I/O stat accounting code

This forces in_flight to be zero when turning off or on the I/O stat
accounting and stops updating I/O stats in attempt_merge() when
accounting is turned off.

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

diff --git a/block/blk-core.c b/block/blk-core.c
index 2557280..3688abf 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -64,12 +64,11 @@ static struct workqueue_struct *kblockd_workqueue;
 
 static void drive_stat_acct(struct request *rq, int new_io)
 {
-       struct gendisk *disk = rq->rq_disk;
        struct hd_struct *part;
        int rw = rq_data_dir(rq);
        int cpu;
 
-       if (!blk_fs_request(rq) || !disk || !blk_do_io_stat(disk->queue))
+       if (!blk_fs_request(rq) || !blk_do_io_stat(rq))
                return;
 
        cpu = part_stat_lock();
@@ -1675,9 +1674,7 @@ EXPORT_SYMBOL(blkdev_dequeue_request);
 
 static void blk_account_io_completion(struct request *req, unsigned int bytes)
 {
-       struct gendisk *disk = req->rq_disk;
-
-       if (!disk || !blk_do_io_stat(disk->queue))
+       if (!blk_do_io_stat(req))
                return;
 
        if (blk_fs_request(req)) {
@@ -1694,9 +1691,7 @@ static void blk_account_io_completion(struct request *req, unsigned int bytes)
 
 static void blk_account_io_done(struct request *req)
 {
-       struct gendisk *disk = req->rq_disk;
-
-       if (!disk || !blk_do_io_stat(disk->queue))
+       if (!blk_do_io_stat(req))
                return;
 
        /*
@@ -1711,7 +1706,7 @@ static void blk_account_io_done(struct request *req)
                int cpu;
 
                cpu = part_stat_lock();
-               part = disk_map_sector_rcu(disk, req->sector);
+               part = disk_map_sector_rcu(req->rq_disk, req->sector);
 
                part_stat_inc(cpu, part, ios[rw]);
                part_stat_add(cpu, part, ticks[rw], duration);

diff --git a/block/blk-merge.c b/block/blk-merge.c
index e39cb24..63760ca 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -338,6 +338,22 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
        return 1;
 }
 
+static void blk_account_io_merge(struct request *req)
+{
+       if (blk_do_io_stat(req)) {
+               struct hd_struct *part;
+               int cpu;
+
+               cpu = part_stat_lock();
+               part = disk_map_sector_rcu(req->rq_disk, req->sector);
+
+               part_round_stats(cpu, part);
+               part_dec_in_flight(part);
+
+               part_stat_unlock();
+       }
+}
+
 /*
  * Has to be called with the request spinlock acquired
  */
@@ -386,18 +402,7 @@ static int attempt_merge(struct request_queue *q, struct request *req,
 
        elv_merge_requests(q, req, next);
 
-       if (req->rq_disk) {
-               struct hd_struct *part;
-               int cpu;
-
-               cpu = part_stat_lock();
-               part = disk_map_sector_rcu(req->rq_disk, req->sector);
-
-               part_round_stats(cpu, part);
-               part_dec_in_flight(part);
-
-               part_stat_unlock();
-       }
+       blk_account_io_merge(req);
 
        req->ioprio = ioprio_best(req->ioprio, next->ioprio);
        if (blk_rq_cpu_valid(next))

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 3ff9bba..73f36be 100644 (file)
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -209,10 +209,14 @@ static ssize_t queue_iostats_store(struct request_queue *q, const char *page,
        ssize_t ret = queue_var_store(&stats, page, count);
 
        spin_lock_irq(q->queue_lock);
+       elv_quisce_start(q);
+
        if (stats)
                queue_flag_set(QUEUE_FLAG_IO_STAT, q);
        else
                queue_flag_clear(QUEUE_FLAG_IO_STAT, q);
+
+       elv_quisce_end(q);
        spin_unlock_irq(q->queue_lock);
 
        return ret;

diff --git a/block/blk.h b/block/blk.h
index 22043c2..24fcaee 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -112,12 +112,14 @@ static inline int blk_cpu_to_group(int cpu)
 #endif
 }
 
-static inline int blk_do_io_stat(struct request_queue *q)
+static inline int blk_do_io_stat(struct request *rq)
 {
-       if (q)
-               return blk_queue_io_stat(q);
+       struct gendisk *disk = rq->rq_disk;
 
-       return 0;
+       if (!disk || !disk->queue)
+               return 0;
+
+       return blk_queue_io_stat(disk->queue) && (rq->cmd_flags & REQ_ELVPRIV);
 }
 
 #endif

diff --git a/block/elevator.c b/block/elevator.c
index c674491..fb81bcc 100644 (file)
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -573,7 +573,7 @@ void elv_requeue_request(struct request_queue *q, struct request *rq)
        elv_insert(q, rq, ELEVATOR_INSERT_REQUEUE);
 }
 
-static void elv_drain_elevator(struct request_queue *q)
+void elv_drain_elevator(struct request_queue *q)
 {
        static int printed;
        while (q->elevator->ops->elevator_dispatch_fn(q, 1))

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 7a20425..c59b769 100644 (file)
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -116,6 +116,7 @@ extern void elv_abort_queue(struct request_queue *);
 extern void elv_completed_request(struct request_queue *, struct request *);
 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 extern void elv_put_request(struct request_queue *, struct request *);
+extern void elv_drain_elevator(struct request_queue *);
 
 /*
  * io scheduler registration