linux-kernel - Re: [Patch] blktrace: remove debugfs entries on bad path

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Message-ID: <4A125ACA.5080107@cn.fujitsu.com>
Date:	Tue, 19 May 2009 15:07:54 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	raspl@...ux.vnet.ibm.com
CC:	linux-btrace@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>,
	linux-kernel@...r.kernel.org, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com
Subject: Re: [Patch] blktrace: remove debugfs entries on bad path

Stefan Raspl wrote:
> Li Zefan wrote:
>> A better title:
>> 	[Patch] blktrace: remove debugfs entries on bad path
>>
>> Stefan Raspl wrote:
>>> debugfs directory entries for devices are not removed on bad path.
>> Can you be more elaborate on how to reproduce this issue?
> 
> It can happen for most bad pathes within do_blk_trace_setup(). One

Now I see what you meant by "bad path". :)

I'd say "some failure pathes", but not "most".

> way to trigger is to set the Vmalloc space via the respective kernel
> parameter to a value that is so small that it will not suffice for
> the 2MB per device and cpu that is required. For instance, set
> vmalloc=10M and start blktrace on a system with 2 cpus on 7 devices.
> Depending on how much Vmalloc space is still free, the final 2 or 3
> devices will fail with a message like this:
> 
> 	BLKTRACESETUP(2) /dev/sdu failed: 5/Input/output error
> 

Yes, this can happen under extreme memory stress.

Thanks for the fix:
	Acked-by: Li Zefan <lizf@...fujitsu.com>

Could you resend the patch to Ingo, with a better title and a better
changelog (but IMHO we don't need to explain how to set up a memory
stress to trigger this issue) and my ack tag? Now blktrace patches
go to Ingo.

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