linux-kernel - Re: [PATCH 2/6] mm/gup: don't pin migrated cma pages in movable zone

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Date:   Thu, 3 Dec 2020 00:01:28 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <akpm@...ux-foundation.org>, <vbabka@...e.cz>, <mhocko@...e.com>,
        <david@...hat.com>, <osalvador@...e.de>,
        <dan.j.williams@...el.com>, <sashal@...nel.org>,
        <tyhicks@...ux.microsoft.com>, <iamjoonsoo.kim@....com>,
        <mike.kravetz@...cle.com>, <rostedt@...dmis.org>,
        <mingo@...hat.com>, <jgg@...pe.ca>, <peterz@...radead.org>,
        <mgorman@...e.de>, <willy@...radead.org>, <rientjes@...gle.com>
Subject: Re: [PATCH 2/6] mm/gup: don't pin migrated cma pages in movable zone

On 12/1/20 9:23 PM, Pavel Tatashin wrote:
> In order not to fragment CMA the pinned pages are migrated. However,
> they are migrated to ZONE_MOVABLE, which also should not have pinned pages.
> 
> Remove __GFP_MOVABLE, so pages can be migrated to zones where pinning
> is allowed.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> ---
>   mm/gup.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index cdb8b9eeb016..3a76c005a3e2 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1610,7 +1610,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
>   	long ret = nr_pages;
>   	struct migration_target_control mtc = {
>   		.nid = NUMA_NO_NODE,
> -		.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_NOWARN,
> +		.gfp_mask = GFP_USER | __GFP_NOWARN,
>   	};
>   
>   check_again:
> 

Reviewed-by: John Hubbard <jhubbard@...dia.com>

...while I was here, I noticed this, which is outside the scope of your patchset, but
I thought I'd just mention it anyway in case anyone cares:

static inline bool is_migrate_movable(int mt)
{
	return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE;
}

...that really should take an "enum migratetype mt" instead of an int, I think.

thanks,
-- 
John Hubbard
NVIDIA