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Subject: Re: [PATCH v2 01/42] mm:gup/writeback: add callbacks for inaccessible
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References: <20200214222658.12946-1-borntraeger@de.ibm.com>
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From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Tue, 18 Feb 2020 17:15:57 +0100
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To: Will Deacon <will@kernel.org>, Sean Christopherson <sean.j.christopherson@intel.com>
Cc: David Hildenbrand <david@redhat.com>, Janosch Frank <frankja@linux.vnet.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, KVM <kvm@vger.kernel.org>, Cornelia Huck <cohuck@redhat.com>, Thomas Huth <thuth@redhat.com>, Ulrich Weigand <Ulrich.Weigand@de.ibm.com>, Claudio Imbrenda <imbrenda@linux.ibm.com>, linux-s390 <linux-s390@vger.kernel.org>, Michael Mueller <mimu@linux.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>, Andrea Arcangeli <aarcange@redhat.com>, linux-mm@kvack.org



On 18.02.20 17:02, Will Deacon wrote:
> On Tue, Feb 18, 2020 at 07:46:10AM -0800, Sean Christopherson wrote:
>> On Tue, Feb 18, 2020 at 09:27:20AM +0100, David Hildenbrand wrote:
>>> On 17.02.20 12:10, Christian Borntraeger wrote:
>>>> So yes, if everything is setup properly this should not fail in real life
>>>> and only we have a kernel (or firmware) bug.
>>>>
>>>
>>> Then, without feedback from other possible users, this should be a void
>>> function. So either introduce error handling or convert it to a void for
>>> now (and add e.g., BUG_ON and a comment inside the s390x implementation).
>>
>> My preference would also be for a void function (versus ignoring an int
>> return).
> 
> The gup code could certainly handle the error value, although the writeback
> is a lot less clear (so a BUG_ON() would seem to be sufficient for now).

Sean, David. Can we agree on merging patch 39?