Re: [PATCH kernel 05/15] powerpc/iommu: Stop using @current in mm_iommu_xxx

On Tue, 9 Aug 2016 14:43:00 +1000
Balbir Singh [off-list ref] wrote:

On 03/08/16 18:40, Alexey Kardashevskiy wrote:

quoted

-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)?

quoted

@@ -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).

Thanks,
Nick