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Date: Wed, 3 Aug 2016 20:10:03 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: linuxppc-dev@lists.ozlabs.org, Alex Williamson
 <alex.williamson@redhat.com>, Paul Mackerras <paulus@samba.org>, David
 Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH kernel 05/15] powerpc/iommu: Stop using @current in
 mm_iommu_xxx
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On Wed,  3 Aug 2016 18:40:46 +1000
Alexey Kardashevskiy <aik@ozlabs.ru> wrote:

> In some situations the userspace memory context may live longer than
> the userspace process itself so if we need to do proper memory context
> cleanup, we better cache @mm and use it later when the process is gone
> (@current or @current->mm are NULL).
> 
> This changes mm_iommu_xxx API to receive mm_struct instead of using one
> from @current.
> 
> This is needed by the following patch to do proper cleanup in time.
> This depends on "powerpc/powernv/ioda: Fix endianness when reading TCEs"
> to do proper cleanup via tce_iommu_clear() patch.
> 
> To keep API consistent, this replaces mm_context_t with mm_struct;
> we stick to mm_struct as mm_iommu_adjust_locked_vm() helper needs
> access to &mm->mmap_sem.
> 
> This should cause no behavioral change.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

I still have some questions about the use of mm in the driver, but
those aren't issues introduced by this patch, so as it is I think
the bug fix of this and the next patch is good.