linux-kernel - Re: [PATCH RESEND block#for-2.6.36] block_dev: always serialize exclusive open attempts

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Message-ID: <4C5A8273.2010803@fusionio.com>
Date:	Thu, 5 Aug 2010 11:20:51 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
CC:	Tejun Heo <htejun@...il.com>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	Linux PM List <linux-pm@...ts.linux-foundation.org>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	Linux Wireless List <linux-wireless@...r.kernel.org>,
	DRI <dri-devel@...ts.freedesktop.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH RESEND block#for-2.6.36] block_dev: always serialize 
 exclusive open attempts

On 2010-08-05 11:17, Markus Trippelsdorf wrote:
> On Thu, Aug 05, 2010 at 11:02:43AM +0200, Jens Axboe wrote:
>> On 2010-08-04 17:59, Tejun Heo wrote:
>>> bd_prepare_to_claim() incorrectly allowed multiple attempts for
>>> exclusive open to progress in parallel if the attempting holders are
>>> identical.  This triggered BUG_ON() as reported in the following bug.
>>>
>>>   https://bugzilla.kernel.org/show_bug.cgi?id=16393
>>>
>>> __bd_abort_claiming() is used to finish claiming blocks and doesn't
>>> work if multiple openers are inside a claiming block.  Allowing
>>> multiple parallel open attempts to continue doesn't gain anything as
>>> those are serialized down in the call chain anyway.  Fix it by always
>>> allowing only single open attempt in a claiming block.
>>>
>>> This problem can easily be reproduced by adding a delay after
>>> bd_prepare_to_claim() and attempting to mount two partitions of a
>>> disk.
>>>
>>> stable: only applicable to v2.6.35
>>>
>>> Signed-off-by: Tejun Heo <tj@...nel.org>
>>> Reported-by: Markus Trippelsdorf <markus@...ppelsdorf.de>
>>> Cc: stable@...nel.org
>>
>> Thanks Tejun, applied.
> 
> It's already in mainline:
> e75aa85892b2ee78c79edac720868cbef16e62eb

Irk, had not noticed yet, my for-2.6.36 branch isn't fully merged
up yet. Thanks for the heads-up.

-- 
Jens Axboe


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