[PATCH v9 04/16] iommu/exynos: allocate lv2 page table from own slab

[Cho KyongHo]

On Fri, 09 Aug 2013 09:55:30 +0200, Tomasz Figa wrote:
> Hi KyongHo,
> 
> On Friday 09 of August 2013 14:58:49 Cho KyongHo wrote:
> > On Thu, 08 Aug 2013 16:00:18 +0200, Tomasz Figa wrote:
> > > On Thursday 08 of August 2013 18:38:04 Cho KyongHo wrote:
> > > > Since kmalloc() does not guarantee that the allignment of 1KiB when
> > > > it
> > > > allocates 1KiB, it is required to allocate lv2 page table from own
> > > > slab that guarantees alignment of 1KiB
> > > > 
> > > > Signed-off-by: Cho KyongHo <pullip.cho at samsung.com>
> > > > ---
> > > > 
> > > >  drivers/iommu/exynos-iommu.c |   24 ++++++++++++++++++++----
> > > >  1 files changed, 20 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/iommu/exynos-iommu.c
> > > > b/drivers/iommu/exynos-iommu.c index d90e6fa..a318049 100644
> > > > --- a/drivers/iommu/exynos-iommu.c
> > > > +++ b/drivers/iommu/exynos-iommu.c
> > > > @@ -100,6 +100,8 @@
> > > > 
> > > >  #define REG_PB1_SADDR		0x054
> > > >  #define REG_PB1_EADDR		0x058
> > > > 
> > > > +static struct kmem_cache *lv2table_kmem_cache;
> > > > +
> > > > 
> > > >  static unsigned long *section_entry(unsigned long *pgtable,
> > > >  unsigned
> > > > 
> > > > long iova) {
> > > > 
> > > >  	return pgtable + lv1ent_offset(iova);
> > > > 
> > > > @@ -765,7 +767,8 @@ static void exynos_iommu_domain_destroy(struct
> > > > iommu_domain *domain)
> > > > 
> > > >  	for (i = 0; i < NUM_LV1ENTRIES; i++)
> > > >  	
> > > >  		if (lv1ent_page(priv->pgtable + i))
> > > > 
> > > > -			kfree(__va(lv2table_base(priv->pgtable + i)));
> > > > +			kmem_cache_free(lv2table_kmem_cache,
> > > > +					__va(lv2table_base(priv->pgtable + 
> i)));
> > > > 
> > > >  	free_pages((unsigned long)priv->pgtable, 2);
> > > >  	free_pages((unsigned long)priv->lv2entcnt, 1);
> > > > 
> > > > @@ -861,7 +864,7 @@ static unsigned long *alloc_lv2entry(unsigned
> > > > long
> > > > *sent, unsigned long iova, if (lv1ent_fault(sent)) {
> > > > 
> > > >  		unsigned long *pent;
> > > > 
> > > > -		pent = kzalloc(LV2TABLE_SIZE, GFP_ATOMIC);
> > > > +		pent = kmem_cache_zalloc(lv2table_kmem_cache, GFP_ATOMIC);
> > > > 
> > > >  		BUG_ON((unsigned long)pent & (LV2TABLE_SIZE - 1));
> > > >  		if (!pent)
> > > >  		
> > > >  			return ERR_PTR(-ENOMEM);
> > > > 
> > > > @@ -881,7 +884,7 @@ static int lv1set_section(unsigned long *sent,
> > > > phys_addr_t paddr, short *pgcnt)
> > > > 
> > > >  	if (lv1ent_page(sent)) {
> > > >  	
> > > >  		BUG_ON(*pgcnt != NUM_LV2ENTRIES);
> > > > 
> > > > -		kfree(page_entry(sent, 0));
> > > > +		kmem_cache_free(lv2table_kmem_cache, page_entry(sent, 0));
> > > > 
> > > >  		*pgcnt = 0;
> > > >  	
> > > >  	}
> > > > 
> > > > @@ -1082,10 +1085,23 @@ static int __init exynos_iommu_init(void)
> > > > 
> > > >  {
> > > >  
> > > >  	int ret;
> > > > 
> > > > +	lv2table_kmem_cache = kmem_cache_create("exynos-iommu-lv2table",
> > > > +				LV2TABLE_SIZE, LV2TABLE_SIZE, 0, NULL);
> > > > +	if (!lv2table_kmem_cache) {
> > > > +		pr_err("%s: Failed to create kmem cache\n", __func__);
> > > > +		return -ENOMEM;
> > > > +	}
> > > > +
> > > > 
> > > >  	ret = platform_driver_register(&exynos_sysmmu_driver);
> > > >  	
> > > >  	if (ret == 0)
> > > > 
> > > > -		bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
> > > > +		ret = bus_set_iommu(&platform_bus_type, 
> &exynos_iommu_ops);
> > > > +
> > > > +	if (ret) {
> > > > +		pr_err("%s: Failed to register exynos-iommu driver.\n",
> > > > +								__func__);
> > > > +		kmem_cache_destroy(lv2table_kmem_cache);
> > > > +	}
> > > 
> > > What about making the return value handling here cleaner? For example:
> > > 	lv2table_kmem_cache = kmem_cache_create("exynos-iommu-lv2table",
> > > 	
> > > 				LV2TABLE_SIZE, LV2TABLE_SIZE, 0, NULL);
> > > 	
> > > 	if (!lv2table_kmem_cache) {
> > > 	
> > > 		...
> > > 		return -ENOMEM;
> > > 	
> > > 	}
> > > 	
> > > 	ret = platform_driver_register(&exynos_sysmmu_driver);
> > > 	if (ret) {
> > > 	
> > > 		...
> > > 		goto err_destroy_kmem_cache;
> > > 	
> > > 	}
> > > 	
> > > 	ret = bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
> > > 	if (ret) {
> > > 	
> > > 		...
> > > 		goto err_platform_unregister;
> > > 	
> > > 	}
> > > 	
> > > 	return 0;
> > > 
> > > err_platform_unregister:
> > > 	...
> > > 
> > > err_destroy_kmem_cache:
> > > 	...
> > > 	return ret;
> > > 
> > > }
> > 
> > Thank you for suggestion.
> > I think you are worrying about missing the information who makes 'ret'
> > non-zero.
> 
> Oh, this is a valid point, but it was more a nitpick about the coding 
> style. Single path error handling (with goto) is widely used in the kernel 
> in cases when more than one thing has to be undone and so I suggested this 
> method of error handling here as well.
> 
> > Ok. I will process it separately.
> 
> Since this patch adds most of the error handling to this function, I think 
> it should be fine to do it as a part of this patch.
> 

I meant 'separately' that checking all return values each.
I think it can be simpler without goto.
There are just 2 cases to rollback previous changes in that function.

> Best regards,
> Tomasz
>