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

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Message-ID: <4A1255E1.1060301@linux.vnet.ibm.com>
Date:	Tue, 19 May 2009 08:46:57 +0200
From:	Stefan Raspl <raspl@...ux.vnet.ibm.com>
To:	Li Zefan <lizf@...fujitsu.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

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
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

Best regards,
Stefan Raspl
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