linux-kernel - Re: [PATCH v9 2/2] Staging: zram: Fix decrement of variable by calling bdput()

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Date:	Fri, 01 Nov 2013 09:54:42 +0100
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Rashika Kheria <rashika.kheria@...il.com>
CC:	opw-kernel@...glegroups.com, Minchan Kim <minchan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchand@...hat.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v9 2/2] Staging: zram: Fix decrement of variable by calling
 bdput()

On 10/31/2013 12:58 PM, Rashika Kheria wrote:
> As suggested by Jerome Marchand "The code in reset_store get the block device
The credit should actually go to Minchan. He found the bug. I merely
explained it.

> (bdget_disk()) but it does not put it (bdput()) when it's done using it.
> The usage count is therefore incremented but never decremented."
> 
> This patch also puts bdput() for all error cases.
> 
> Cc: stable@...r.kernel.org 
> Signed-off-by: Rashika Kheria <rashika.kheria@...il.com>

This version finally looks good. Thanks for your effort.

Acked-by: Jerome Marchand <jmarchan@...hat.com>

> ---
> 
> This revision fixes the following issues of the previous revision-
> Proper error handling
> 
>  drivers/staging/zram/zram_drv.c |   19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 012ba15..a1f8b1f 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -652,21 +652,30 @@ static ssize_t reset_store(struct device *dev,
>  		return -ENOMEM;
>  
>  	/* Do not reset an active device! */
> -	if (bdev->bd_holders)
> -		return -EBUSY;
> +	if (bdev->bd_holders) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
>  
>  	ret = kstrtou16(buf, 10, &do_reset);
>  	if (ret)
> -		return ret;
> +		goto out;
>  
> -	if (!do_reset)
> -		return -EINVAL;
> +	if (!do_reset) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>  
>  	/* Make sure all pending I/O is finished */
>  	fsync_bdev(bdev);
> +	bdput(bdev);
>  
>  	zram_reset_device(zram, true);
>  	return len;
> +
> +out:	
> +	bdput(bdev);
> +	return ret;
>  }
>  
>  static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
> 

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