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

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Message-ID: <20100805091704.GA1772@arch.tripp.de>
Date:	Thu, 5 Aug 2010 11:17:04 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Jens Axboe <jaxboe@...ionio.com>
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 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

-- 
»A man who doesn't know he is in prison can never escape.«
William S. Burroughs
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