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

[Jens Axboe]

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 at kernel.org>
> Reported-by: Markus Trippelsdorf <markus at trippelsdorf.de>
> Cc: stable at kernel.org

Thanks Tejun, applied.

-- 
Jens Axboe


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