md: fix md io stats accounting broken

commit 74672d069b298b03e9f657fd70915e055739882e upstream.

Simon reported the md io stats accounting issue:
"
I'm seeing "iostat -x -k 1" print this after a RAID1 rebuild on 4.0-rc5.
It's not abnormal other than it's 3-disk, with one being SSD (sdc) and
the other two being write-mostly:

Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
sdb               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
sdc               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
md0               0.00     0.00    0.00    0.00     0.00     0.00     0.00   345.00    0.00    0.00    0.00   0.00 100.00
md2               0.00     0.00    0.00    0.00     0.00     0.00     0.00 58779.00    0.00    0.00    0.00   0.00 100.00
md1               0.00     0.00    0.00    0.00     0.00     0.00     0.00    12.00    0.00    0.00    0.00   0.00 100.00
"
The cause is commit "18c0b223cf9901727ef3b02da6711ac930b4e5d4" uses the
generic_start_io_acct to account the disk stats rather than the open code,
but it also introduced the increase to .in_flight[rw] which is needless to
md. So we re-use the open code here to fix it.

Reported-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 709755fb6d7b62823d2291c99397ca0111adcbaf..193feb92c320c717db7a2016ce9eb181f579c27f 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -248,6 +248,7 @@ static void md_make_request(struct request_queue *q, struct bio *bio)
        const int rw = bio_data_dir(bio);
        struct mddev *mddev = q->queuedata;
        unsigned int sectors;
+       int cpu;
 
        if (mddev == NULL || mddev->pers == NULL
            || !mddev->ready) {
@@ -283,7 +284,10 @@ static void md_make_request(struct request_queue *q, struct bio *bio)
        sectors = bio_sectors(bio);
        mddev->pers->make_request(mddev, bio);
 
-       generic_start_io_acct(rw, sectors, &mddev->gendisk->part0);
+       cpu = part_stat_lock();
+       part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
+       part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw], sectors);
+       part_stat_unlock();
 
        if (atomic_dec_and_test(&mddev->active_io) && mddev->suspended)
                wake_up(&mddev->sb_wait);