linux-kernel - Re: [PATCH RFC v3 04/35] mm: page_alloc: Partially revert "mm: page

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Date: Mon, 29 Jan 2024 14:31:23 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Alexandru Elisei <alexandru.elisei@....com>, catalin.marinas@....com,
 will@...nel.org, oliver.upton@...ux.dev, maz@...nel.org,
 james.morse@....com, suzuki.poulose@....com, yuzenghui@...wei.com,
 arnd@...db.de, akpm@...ux-foundation.org, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
 mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
 mhiramat@...nel.org, rppt@...nel.org, hughd@...gle.com
Cc: pcc@...gle.com, steven.price@....com, vincenzo.frascino@....com,
 david@...hat.com, eugenis@...gle.com, kcc@...gle.com, hyesoo.yu@...sung.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-mm@...ck.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v3 04/35] mm: page_alloc: Partially revert "mm:
 page_alloc: remove stale CMA guard code"



On 1/25/24 22:12, Alexandru Elisei wrote:
> The patch f945116e4e19 ("mm: page_alloc: remove stale CMA guard code")
> removed the CMA filter when allocating from the MIGRATE_MOVABLE pcp list
> because CMA is always allowed when __GFP_MOVABLE is set.
> 
> With the introduction of the arch_alloc_cma() function, the above is not
> true anymore, so bring back the filter.

This makes sense as arch_alloc_cma() now might prevent ALLOC_CMA being
assigned to alloc_flags in gfp_to_alloc_flags_cma().

> 
> This is a partially revert because the stale comment remains removed.
> 
> Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
> ---
>  mm/page_alloc.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a96d47a6393e..0fa34bcfb1af 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2897,10 +2897,17 @@ struct page *rmqueue(struct zone *preferred_zone,
>  	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
>  
>  	if (likely(pcp_allowed_order(order))) {
> -		page = rmqueue_pcplist(preferred_zone, zone, order,
> -				       migratetype, alloc_flags);
> -		if (likely(page))
> -			goto out;
> +		/*
> +		 * MIGRATE_MOVABLE pcplist could have the pages on CMA area and
> +		 * we need to skip it when CMA area isn't allowed.
> +		 */
> +		if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA ||
> +				migratetype != MIGRATE_MOVABLE) {
> +			page = rmqueue_pcplist(preferred_zone, zone, order,
> +					migratetype, alloc_flags);
> +			if (likely(page))
> +				goto out;
> +		}
>  	}
>  
>  	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,