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>

1 files changed, 4 insertions, 9 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 25572802dac2..3688abff2430 100644
--- 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);