linux-kernel - Re: [PATCH 3/3] blktrace: fix the original blktrace

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Message-ID: <49CC1C0D.1000901@cn.fujitsu.com>
Date:	Fri, 27 Mar 2009 08:21:33 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] blktrace: fix the original blktrace

>>> Yeah. Li, Arnaldo, what do you think?
>>>
>>> Delaying them would be quite painful at this stage though - the 
>>> blktrace plugin conversion was done with (ahem) your initial support 
>>> so the commits got (foolishly, in hindsight ;-) interwoven into 300 
>>> commits of the 2.6.30 tracing tree.
>>>
>>> Delaying them would also be technically baseless - there are no 
>>> known regressions or bugs in this code. (If you know about bugs then 
>>> please speak up so we can fix them! ;-)
>>>

I do know some bugs. ;)

>>> At this last minute stage we can do two things: merge it now or if 
>>> you NAK it then we'll rebase the last ~2 months of the tracing tree 
>>> with hundreds of commits (sigh), destroy its true history in the 
>>> process and eradicate the blktrace bits.
>>>
>>> I'd like to avoid the second option if possible as it destroys real 
>>> value (these changes are really nice improvements, a lot of work 
>>> went into them and there's no open regressions so i can see no 
>>> objective reason why they couldnt go upstream now) but it's your 
>>> choice really, you maintain block/* :-)
>> Well, after this set of fixes by Li the only problem I'm aware of is the
>> __trace_note_message, that is using ftrace_vprintk, that I didn't notice

This was the first issue I saw when I started to use blktrace in -tip tree,
and I made a fix yesterday. I'll post it soon, with some other fixes.

>> because I wasn't using CFQ when developing it, and that gets the output
>> of the _ftrace_ plugin wedged, but that doesn't affect normal blktrace
>> operation.
>>
>> I'll try to get that fixed somehow today, other than that I'm not aware
>> of any other problem, so I think it could get into 2.6.30 on the premise
>> that normal blktrace operation is as stable as before and that the
>> ftrace plugin is recent work and may still need some fixes.
> 
> Well, judging whether it is as stable as before is exactly what is asked
> of you and Li :-). So which is it?
> 

With the fixes I posted and will post, both ioctl-based blktrace and ftrace
-based blktrace should be working fine, and I'll continue to use and test
it.
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