linux-kernel - Re: [PATCH] mm/page_alloc: fix memalloc_nocma

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Message-ID: <20200721120533.GD15516@casper.infradead.org>
Date:   Tue, 21 Jul 2020 13:05:33 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     js1304@...il.com
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@....com,
        Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, stable@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs

On Tue, Jul 21, 2020 at 12:28:49PM +0900, js1304@...il.com wrote:
> +static inline unsigned int current_alloc_flags(gfp_t gfp_mask,
> +					unsigned int alloc_flags)
> +{
> +#ifdef CONFIG_CMA
> +	unsigned int pflags = current->flags;
> +
> +	if (!(pflags & PF_MEMALLOC_NOCMA) &&
> +		gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
> +		alloc_flags |= ALLOC_CMA;

Please don't indent by one tab when splitting a line because it looks like
the second line and third line are part of the same block.  Either do
this:

	if (!(pflags & PF_MEMALLOC_NOCMA) &&
	    gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
		alloc_flags |= ALLOC_CMA;

or this:
	if (!(pflags & PF_MEMALLOC_NOCMA) &&
			gfp_migratetype(gfp_mask) == MIGRATE_MOVABLE)
		alloc_flags |= ALLOC_CMA;

> @@ -4619,8 +4631,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  		wake_all_kswapds(order, gfp_mask, ac);
>  
>  	reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
> -	if (reserve_flags)
> +	if (reserve_flags) {
>  		alloc_flags = reserve_flags;
> +		alloc_flags = current_alloc_flags(gfp_mask, alloc_flags);
> +	}

Is this right?  Shouldn't you be passing reserve_flags to
current_alloc_flags() here?  Also, there's no need to add { } here.