Re: [PATCH] Replace obscure constructs in fs/block_dev.c

["Björn Steinbrink" <B.Steinbrink@gmx.de>]

On 2007.06.15 15:46:32 +0200, Johannes Weiner wrote:
> Hi,
> 
> Andrew, I promised it [1], here goes. Patched against Linus' git-tree.
> 
> [1] http://lkml.org/lkml/2007/3/22/226
> 
> This patch replaces some obscure code-paths in fs/block_dev.c with more
> readable versions.
> 
> Signed-off-by: Johannes Weiner <hannes-kernel@saeurebad.de>
> 

> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index ea1480a..1ffbb6d 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -660,26 +660,16 @@ void bd_forget(struct inode *inode)
>  
>  int bd_claim(struct block_device *bdev, void *holder)
>  {
> -	int res;
> +	int res = 0;
>  	spin_lock(&bdev_lock);
>  
> -	/* first decide result */
> -	if (bdev->bd_holder == holder)
> -		res = 0;	 /* already a holder */
> -	else if (bdev->bd_holder != NULL)
> -		res = -EBUSY; 	 /* held by someone else */
> -	else if (bdev->bd_contains == bdev)
> -		res = 0;  	 /* is a whole device which isn't held */
> -
> -	else if (bdev->bd_contains->bd_holder == bd_claim)
> -		res = 0; 	 /* is a partition of a device that is being partitioned */
> -	else if (bdev->bd_contains->bd_holder != NULL)
> -		res = -EBUSY;	 /* is a partition of a held device */
> -	else
> -		res = 0;	 /* is a partition of an un-held device */
> +	/* If already held by someone else or we have a
> +	 * partition of a held device, we do nothing. */
>  
> -	/* now impose change */
> -	if (res==0) {
> +	if (bdev->bd_holder || bdev->bd_contains->bd_holder)
> +		res = -EBUSY;

Hm, that actually ignores the "someone else" part of the comment and
introduces a semantic change. No idea, if it breaks anything though.

Björn