linux-kernel - Re: [PATCH] block: use the passed in @bdev when claiming if partno is zero

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Date:	Mon, 13 Jun 2011 14:44:18 +0200
From:	Jens Axboe <axboe@...nel.dk>
To:	Tejun Heo <tj@...nel.org>
CC:	linux-kernel@...r.kernel.org, stable@...nel.org,
	avillaci@...bo.fiec.espol.edu.ec
Subject: Re: [PATCH] block: use the passed in @bdev when claiming if partno
 is  zero

On 2011-06-13 12:44, Tejun Heo wrote:
> 6b4517a791 (block: implement bd_claiming and claiming block)
> introduced claiming block to support O_EXCL blkdev opens properly.
> 
> bd_start_claiming() looks up the part 0 bdev and starts claiming
> block.  The function assumed that there is only one part 0 bdev and
> always used bdget_disk(disk, 0) to look it up; unfortunately, this
> isn't true for some drivers (floppy) which use multiple block devices
> to denote different operating parameters for the same physical device.
> There can be multiple part 0 bdev's for the same device number.
> 
> This incorrect assumption caused the wrong bdev to be used during
> claiming leading to unbalanced bd_holders as reported in the following
> bug.
> 
>   https://bugzilla.kernel.org/show_bug.cgi?id=28522
> 
> This patch updates bd_start_claiming() such that it uses the bdev
> specified as argument if its partno is zero.
> 
> Note that this means that different bdev's can be used for the same
> device and O_EXCL check can be effectively bypassed.  It has always
> been broken that way and floppy is fortunately on its way out.  Leave
> that breakage alone.

Thanks, applied for 3.0.

-- 
Jens Axboe

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