linux-kernel - Re: [PATCH] kvm/eventfd: fix the misleading comment in kvm_irqfd

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Message-ID: <c6b7c933-2d48-1504-7c45-110b0ab317ad@linux.ibm.com>
Date:   Mon, 29 Nov 2021 18:13:39 +0100
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     "Longpeng(Mike)" <longpeng2@...wei.com>, pbonzini@...hat.com
Cc:     cornelia.huck@...ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, arei.gonglei@...wei.com
Subject: Re: [PATCH] kvm/eventfd: fix the misleading comment in
 kvm_irqfd_assign



Am 29.11.21 um 04:43 schrieb Longpeng(Mike):
> From: Longpeng <longpeng2@...wei.com>
> 
> The comment above the invocation of vfs_poll() is misleading, move
> it to the right place.
> 
I think that the current variant is better.
events is only used in that function to check for EPOLLIN, so the
assignment and the if belong together from a "what am I doing here" perspective.

> Fixes: 684a0b719ddb ("KVM: eventfd: Fix lock order inversion")
> Signed-off-by: Longpeng <longpeng2@...wei.com>
> ---
>   virt/kvm/eventfd.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index 2ad013b..cd01814 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -406,12 +406,12 @@ bool __attribute__((weak)) kvm_arch_irqfd_route_changed(
> 
>   	spin_unlock_irq(&kvm->irqfds.lock);
> 
> +	events = vfs_poll(f.file, &irqfd->pt);
> +
>   	/*
>   	 * Check if there was an event already pending on the eventfd
>   	 * before we registered, and trigger it as if we didn't miss it.
>   	 */
> -	events = vfs_poll(f.file, &irqfd->pt);
> -
>   	if (events & EPOLLIN)
>   		schedule_work(&irqfd->inject);
>