linux-kernel - Re: [PATCH 09/27] mm: generalize the pgmap based page

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Date:   Mon, 14 Feb 2022 10:37:43 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Felix Kuehling <Felix.Kuehling@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org
Subject: Re: [PATCH 09/27] mm: generalize the pgmap based page_free
 infrastructure



On 2022-02-10 12:28 a.m., Christoph Hellwig wrote:
> Key off on the existence of ->page_free to prepare for adding support for
> more pgmap types that are device managed and thus need the free callback.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Great! This makes my patch simpler.

Reviewed-by: Logan Gunthorpe <logang@...tatee.com>


> ---
>  mm/memremap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memremap.c b/mm/memremap.c
> index fef5734d5e4933..e00ffcdba7b632 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -452,7 +452,7 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
>  
>  void free_zone_device_page(struct page *page)
>  {
> -	if (WARN_ON_ONCE(!is_device_private_page(page)))
> +	if (WARN_ON_ONCE(!page->pgmap->ops || !page->pgmap->ops->page_free))
>  		return;
>  
>  	__ClearPageWaiters(page);
> @@ -460,7 +460,7 @@ void free_zone_device_page(struct page *page)
>  	mem_cgroup_uncharge(page_folio(page));
>  
>  	/*
> -	 * When a device_private page is freed, the page->mapping field
> +	 * When a device managed page is freed, the page->mapping field
>  	 * may still contain a (stale) mapping value. For example, the
>  	 * lower bits of page->mapping may still identify the page as an
>  	 * anonymous page. Ultimately, this entire field is just stale
>