md: fix md io stats accounting broken

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>
Cc: <stable@vger.kernel.org> 3.19
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 717daad71fb101b2b97efd03b1bb41d8b35ecfe7..e6178787ce3dd4a9b0e33b80b72ac39f73e25e33 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -249,6 +249,7 @@ 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) {
@@ -284,7 +285,10 @@ 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);