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

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Message-ID: <20140916223402.GL15807@hpx.cz>
Date:	Wed, 17 Sep 2014 00:34:05 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Andres Lagar-Cavilla <andreslc@...gle.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

[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.

> >> 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>

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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