linux-kernel - Re: [PATCH] kvm: Faults which trigger IO release the mmap

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Message-ID: <CAJu=L5-UPXzxnM0D2Z2Rgn7Cgv_4HpKiHz4e475gp7m2fa3bzQ@mail.gmail.com>
Date:	Tue, 16 Sep 2014 21:15:06 -0700
From:	Andres Lagar-Cavilla <andreslc@...gle.com>
To:	Radim Krčmář <rkrcmar@...hat.com>
Cc:	Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...hat.com>, Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] kvm: Faults which trigger IO release the mmap_sem

On Tue, Sep 16, 2014 at 3:34 PM, Radim Krčmář <rkrcmar@...hat.com> wrote:
> [Emergency posting to fix the tag and couldn't find unmangled Cc list,
>  so some recipients were dropped, sorry.  (I guess you are glad though).]
>
> 2014-09-16 14:01-0700, Andres Lagar-Cavilla:
>> On Tue, Sep 16, 2014 at 1:51 PM, Radim Krčmář <rkrcmar@...hat.com> wrote:
>> > 2014-09-15 13:11-0700, Andres Lagar-Cavilla:
>> >> +int kvm_get_user_page_retry(struct task_struct *tsk, struct
>> >> mm_struct *mm,
>> >
>> > The suffix '_retry' is not best suited for this.
>> > On first reading, I imagined we will be retrying something from
>> > before,
>> > possibly calling it in a loop, but we are actually doing the first and
>> > last try in one call.
>>
>> We are doing ... the second and third in most scenarios. async_pf did
>> the first with _NOWAIT. We call this from the async pf retrier, or if
>> async pf couldn't be notified to the guest.
>
> I was thinking more about what the function does, not how we currently
> use it -- nothing prevents us from using it as first somewhere -- but
> yeah, even comments would be off then.
>

Good point. Happy to expand comments. What about _complete? _io? _full?

>> >> Apart from this, the patch looks good.  The mm/ parts are minimal, so
>> >> I
>> >> think it's best to merge it through the KVM tree with someone's
>> >> Acked-by.
>> >
>> > I would prefer to have the last hunk in a separate patch, but still,
>> >
>> > Acked-by: Radim Krčmář <rkrcmar@...hat.com>
>>
>> Awesome, thanks much.
>>
>> I'll recut with the VM_BUG_ON from Paolo and your Ack. LMK if anything
>> else from this email should go into the recut.
>
> Ah, sorry, I'm not maintaining mm ... what I meant was
>
> Reviewed-by: Radim Krčmář <rkrcmar@...hat.com>

Cool cool cool
Andres

>
> and I had to leave before I could find a good apology for
> VM_WARN_ON_ONCE(), so if you are replacing BUG_ON, you might want to
> look at that one as well.
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