linux-kernel - Re: [PATCH] MM: discard __GFP

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Date:   Wed, 17 Nov 2021 13:18:25 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     NeilBrown <neilb@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Thierry Reding <thierry.reding@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MM: discard __GFP_ATOMIC

On Wed, Nov 17, 2021 at 03:39:30PM +1100, NeilBrown wrote:
> +++ b/drivers/iommu/tegra-smmu.c
> @@ -676,12 +676,12 @@ static struct page *as_get_pde_page(struct tegra_smmu_as *as,
>  	 * allocate page in a sleeping context if GFP flags permit. Hence
>  	 * spinlock needs to be unlocked and re-locked after allocation.
>  	 */
> -	if (!(gfp & __GFP_ATOMIC))
> +	if (gfp & __GFP_DIRECT_RECLAIM)
>  		spin_unlock_irqrestore(&as->lock, *flags);
>  
>  	page = alloc_page(gfp | __GFP_DMA | __GFP_ZERO);
>  
> -	if (!(gfp & __GFP_ATOMIC))
> +	if (gfp & __GFP_DIRECT_RECLAIM)
>  		spin_lock_irqsave(&as->lock, *flags);
>  
>  	/*

Surely this should be gfpflags_allow_blocking() instead of poking about
in the innards of gfp flags?

This patch seems like a good simplification to me.

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>