linux-kernel - Re: [PATCH] blk-cgroup: Fix the recursive blkg rwstat

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Date:   Sun, 7 Mar 2021 07:42:10 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Xunlei Pang <xlpang@...ux.alibaba.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-cgroup: Fix the recursive blkg rwstat

On Fri, Mar 05, 2021 at 11:32:05AM -0700, Jens Axboe wrote:
> On 3/5/21 1:13 AM, Xunlei Pang wrote:
> > The current blkio.throttle.io_service_bytes_recursive doesn't
> > work correctly.
> > 
> > As an example, for the following blkcg hierarchy:
> >  (Made 1GB READ in test1, 512MB READ in test2)
> >      test
> >     /    \
> >  test1   test2
> > 
> > $ head -n 1 test/test1/blkio.throttle.io_service_bytes_recursive
> > 8:0 Read 1073684480
> > $ head -n 1 test/test2/blkio.throttle.io_service_bytes_recursive
> > 8:0 Read 537448448
> > $ head -n 1 test/blkio.throttle.io_service_bytes_recursive
> > 8:0 Read 537448448
> > 
> > Clearly, above data of "test" reflects "test2" not "test1"+"test2".
> > 
> > Do the correct summary in blkg_rwstat_recursive_sum().
> 
> LGTM, Tejun?

Gees, that's horrible. Thanks for fixing this.

Acked-by: Tejun Heo <tj@...nel.org>

-- 
tejun