linux-kernel - Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free

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Message-ID: <5552EF78.6020301@ozlabs.ru>
Date:	Wed, 13 May 2015 16:30:16 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	Gavin Shan <gwshan@...ux.vnet.ibm.com>
CC:	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table
 in iommu_free_table()

On 05/13/2015 03:33 PM, Gavin Shan wrote:
> On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote:
>> At the moment iommu_free_table() only releases memory if
>> the table was initialized for the platform code use, i.e. it had
>> it_map initialized (which purpose is to track DMA memory space use).
>>
>> With dynamic DMA windows, we will need to be able to release
>> iommu_table even if it was used for VFIO in which case it_map is NULL
>> so does the patch.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
>
> Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
>
>> ---
>> arch/powerpc/kernel/iommu.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
>> index 3d47eb3..2c02d4c 100644
>> --- a/arch/powerpc/kernel/iommu.c
>> +++ b/arch/powerpc/kernel/iommu.c
>> @@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
>> 	unsigned int order;
>>
>> 	if (!tbl || !tbl->it_map) {
>> -		printk(KERN_ERR "%s: expected TCE map for %s\n", __func__,
>> -				node_name);
>> +		kfree(tbl);
>
> I'm not sure if the "tbl" needs to be checked against NULL as kfree() already
> has the check. But it looks a bit strange to free NULL "tbl" from the code
> itself.

Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/... 
- they all check the passed pointer for NULL.



-- 
Alexey
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