linux-kernel - Re: [PATCH v2 2/2] iova: Remove magazine BUG

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Date:   Mon, 5 Sep 2022 08:06:30 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     John Garry <john.garry@...wei.com>
Cc:     robin.murphy@....com, joro@...tes.org, will@...nel.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [PATCH v2 2/2] iova: Remove magazine BUG_ON() checks

On Mon, Sep 05, 2022 at 05:11:23PM +0800, John Garry wrote:
> Two of the magazine helpers have BUG_ON() checks, as follows:
> - iova_magazine_pop() - here we ensure that the mag is not empty. However we
>   already ensure that in the only caller, __iova_rcache_get().
> - iova_magazine_push() - here we ensure that the mag is not full. However
>   we already ensure that in the only caller, __iova_rcache_insert().
> 
> As described, the two bug checks are pointless so drop them.
> 
> Signed-off-by: John Garry <john.garry@...wei.com>
> Acked-by: Robin Murphy <robin.murphy@....com>

Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com

> ---
>  drivers/iommu/iova.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index 580fdf669922..8aece052ce72 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -694,8 +694,6 @@ static unsigned long iova_magazine_pop(struct iova_magazine *mag,
>  	int i;
>  	unsigned long pfn;
>  
> -	BUG_ON(iova_magazine_empty(mag));
> -
>  	/* Only fall back to the rbtree if we have no suitable pfns at all */
>  	for (i = mag->size - 1; mag->pfns[i] > limit_pfn; i--)
>  		if (i == 0)
> @@ -710,8 +708,6 @@ static unsigned long iova_magazine_pop(struct iova_magazine *mag,
>  
>  static void iova_magazine_push(struct iova_magazine *mag, unsigned long pfn)
>  {
> -	BUG_ON(iova_magazine_full(mag));
> -
>  	mag->pfns[mag->size++] = pfn;
>  }
>  
> -- 
> 2.35.3
>