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Subject: Re: [PATCH kernel 05/15] powerpc/iommu: Stop using @current in
 mm_iommu_xxx
To: Nicholas Piggin <nicholas.piggin@gmail.com>
References: <1470213656-1042-1-git-send-email-aik@ozlabs.ru>
 <1470213656-1042-6-git-send-email-aik@ozlabs.ru>
 <cb29b1f1-8ba0-56e5-004c-59d38bbcd3ba@gmail.com>
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Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, linuxppc-dev@lists.ozlabs.org,
 Alex Williamson <alex.williamson@redhat.com>,
 Paul Mackerras <paulus@samba.org>, David Gibson <david@gibson.dropbear.id.au>
From: Balbir Singh <bsingharora@gmail.com>
Message-ID: <52646f18-e8af-31c5-2eea-a70a043aad67@gmail.com>
Date: Tue, 9 Aug 2016 16:17:16 +1000
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On 09/08/16 16:04, Nicholas Piggin wrote:
> On Tue, 9 Aug 2016 14:43:00 +1000
> Balbir Singh <bsingharora@gmail.com> wrote:
> 
>> On 03/08/16 18:40, Alexey Kardashevskiy wrote:
> 
>>> -long mm_iommu_get(unsigned long ua, unsigned long entries,
>>> +long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>>>  		struct mm_iommu_table_group_mem_t **pmem)
>>>  {
>>>  	struct mm_iommu_table_group_mem_t *mem;
>>>  	long i, j, ret = 0, locked_entries = 0;
>>>  	struct page *page = NULL;
>>>  
>>> -	if (!current || !current->mm)
>>> -		return -ESRCH; /* process exited */  
>>
>> VM_BUG_ON(mm == NULL)?
> 
> 
>>> @@ -128,10 +129,17 @@ static long tce_iommu_register_pages(struct tce_container *container,
>>>  			((vaddr + size) < vaddr))
>>>  		return -EINVAL;
>>>  
>>> -	ret = mm_iommu_get(vaddr, entries, &mem);
>>> +	if (!container->mm) {
>>> +		if (!current->mm)
>>> +			return -ESRCH; /* process exited */  
>>
>> You may even want to check for PF_EXITING and ignore those tasks?
> 
> 
> These are related to some of the questions I had about the patch.
> 
> But I think it makes sense just to take this approach as a minimal
> bug fix without changing logic too much or adding BUG_ONs, and then
> if we we can consider how iommu takes references to mm and uses it
> (if anybody finds the time).
> 

Agreed

Balbir