Patch "md: fix md io stats accounting broken" has been added to the 4.0-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    md: fix md io stats accounting broken

to the 4.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     md-fix-md-io-stats-accounting-broken.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 74672d069b298b03e9f657fd70915e055739882e Mon Sep 17 00:00:00 2001
From: Gu Zheng <guz.fnst@cn.fujitsu.com>
Date: Fri, 3 Apr 2015 08:44:47 +0800
Subject: md: fix md io stats accounting broken

From: Gu Zheng <guz.fnst@cn.fujitsu.com>

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>

---
 drivers/md/md.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -249,6 +249,7 @@ static void md_make_request(struct reque
 	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 reque
 	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);


Patches currently in stable-queue which might be from guz.fnst@cn.fujitsu.com are

queue-4.0/md-fix-md-io-stats-accounting-broken.patch