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Date: Wed, 16 Jan 2013 10:53:26 +0800
From: Fengguang Wu <fengguang.wu@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        linux-kernel@vger.kernel.org, chavey@google.com
Subject: Re: [PATCH v2] writeback: mark sysctl vm.block_dump for removal
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On Wed, Jan 16, 2013 at 03:07:53AM +0100, Jan Kara wrote:
> On Tue 15-01-13 08:28:13, Tejun Heo wrote:
> > vm.block_dump is nasty in that it dumps IO traces directly to printk.
> > It isn't scalable and can easily lead to looping behavior - IO
> > generating kernel message which in turn genreates log IO, ad
> > infinitum.
> > 
> > Now that proper tracepoints are in place, vm.block_dump isn't
> > necessary.  Generate a warning if used so that it can be removed down
> > the road.

> > +	if (!warned && block_dump) {
> > +		pr_warning("sysctl: vm.block_dump is scheduled for removal. Use tracepoints instead.\n");
> > +		pr_warning("sysctl: Please contact Jens Axboe <axboe@kernel.dk> if you require this.\n");
> > +		warned = true;

Looks good to me. A warning in dmesg is pertinent because the
block_dump users will be looking at dmesg for block dump results.

Hmm, perhaps a more practical tip on the usage of replacement
tracepoints or tool will help eliminate some user emails to Jens.

> > diff --git a/patches/series b/patches/series
> > index 9fb9bfe..b2582cb 100644
> > --- a/patches/series
> > +++ b/patches/series
> > @@ -18,3 +18,4 @@ kill-pool-gcwq
> >  remove-gcwq
> >  rename-nr_running
> >  cleanup-leftovers
> > +dbg

An extra chunk.

Reviewed-by: Fengguang Wu <fengguang.wu@intel.com>

Thanks!