linux-kernel - Re: [PATCH kernel v8 21/31] powerpc/iommu: Split iommu_free

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Date:	Thu, 16 Apr 2015 16:46:37 +1000
From:	David Gibson <david@...son.dropbear.id.au>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	linuxppc-dev@...ts.ozlabs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v8 21/31] powerpc/iommu: Split iommu_free_table
 into 2 helpers

On Fri, Apr 10, 2015 at 04:31:03PM +1000, Alexey Kardashevskiy wrote:
> The iommu_free_table helper release memory it is using (the TCE table and
> @it_map) and release the iommu_table struct as well. We might not want
> the very last step as we store iommu_table in parent structures.

Yeah, as I commented on the earlier patch, freeing the surrounding
group from a function taking just the individual table is wrong.

> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> ---
>  arch/powerpc/include/asm/iommu.h |  1 +
>  arch/powerpc/kernel/iommu.c      | 57 ++++++++++++++++++++++++----------------
>  2 files changed, 35 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index bde7ee7..8ed4648 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -127,6 +127,7 @@ static inline void *get_iommu_table_base(struct device *dev)
>  
>  extern struct iommu_table *iommu_table_alloc(int node);
>  /* Frees table for an individual device node */
> +extern void iommu_reset_table(struct iommu_table *tbl, const char *node_name);
>  extern void iommu_free_table(struct iommu_table *tbl, const char *node_name);
>  
>  /* Initializes an iommu_table based in values set in the passed-in
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 501e8ee..0bcd988 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -721,24 +721,46 @@ struct iommu_table *iommu_table_alloc(int node)
>  	return &table_group->tables[0];
>  }
>  
> +void iommu_reset_table(struct iommu_table *tbl, const char *node_name)
> +{
> +	if (!tbl)
> +		return;
> +
> +	if (tbl->it_map) {
> +		unsigned long bitmap_sz;
> +		unsigned int order;
> +
> +		/*
> +		 * In case we have reserved the first bit, we should not emit
> +		 * the warning below.
> +		 */
> +		if (tbl->it_offset == 0)
> +			clear_bit(0, tbl->it_map);
> +
> +		/* verify that table contains no entries */
> +		if (!bitmap_empty(tbl->it_map, tbl->it_size))
> +			pr_warn("%s: Unexpected TCEs for %s\n", __func__,
> +					node_name);
> +
> +		/* calculate bitmap size in bytes */
> +		bitmap_sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
> +
> +		/* free bitmap */
> +		order = get_order(bitmap_sz);
> +		free_pages((unsigned long) tbl->it_map, order);
> +	}
> +
> +	memset(tbl, 0, sizeof(*tbl));
> +}
> +
>  void iommu_free_table(struct iommu_table *tbl, const char *node_name)
>  {
> -	unsigned long bitmap_sz;
> -	unsigned int order;
>  	struct iommu_table_group *table_group = tbl->it_group;
>  
> -	if (!tbl || !tbl->it_map) {
> -		printk(KERN_ERR "%s: expected TCE map for %s\n", __func__,
> -				node_name);
> +	if (!tbl)
>  		return;
> -	}
>  
> -	/*
> -	 * In case we have reserved the first bit, we should not emit
> -	 * the warning below.
> -	 */
> -	if (tbl->it_offset == 0)
> -		clear_bit(0, tbl->it_map);
> +	iommu_reset_table(tbl, node_name);
>  
>  #ifdef CONFIG_IOMMU_API
>  	if (table_group->group) {
> @@ -747,17 +769,6 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
>  	}
>  #endif
>  
> -	/* verify that table contains no entries */
> -	if (!bitmap_empty(tbl->it_map, tbl->it_size))
> -		pr_warn("%s: Unexpected TCEs for %s\n", __func__, node_name);
> -
> -	/* calculate bitmap size in bytes */
> -	bitmap_sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
> -
> -	/* free bitmap */
> -	order = get_order(bitmap_sz);
> -	free_pages((unsigned long) tbl->it_map, order);
> -
>  	/* free table */
>  	kfree(table_group);
>  }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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