linux-kernel - Re: [RFC PATCH] vfio: type1: fix kthread use case

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Date:   Tue, 7 Jul 2020 08:04:54 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Hillf Danton <hdanton@...a.com>, iommu@...ts.linux-foundation.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alex Williamson <alex.williamson@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Jörg Rödel <joro@...tes.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Yan Zhao <yan.y.zhao@...el.com>
Subject: Re: [RFC PATCH] vfio: type1: fix kthread use case

…
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2798,7 +2798,7 @@ static int vfio_iommu_type1_dma_rw_chunk
…
> -	bool kthread = current->mm == NULL;
> +	bool kthread_load_mm;
>  	size_t offset;

How do you think about to reduce the scope for such variables?
https://refactoring.com/catalog/reduceScopeOfVariable.html


…
> @@ -2812,11 +2812,12 @@ static int vfio_iommu_type1_dma_rw_chunk
…
>  	if (!mm)
>  		return -EPERM;
…
> +	kthread_load_mm = current->flags & PF_KTHREAD &&
> +				current->mm == NULL;
…

Would you like to apply a more succinct code variant?

+	kthread_load_mm = current->flags & PF_KTHREAD && !current->mm;


Regards,
Markus