linux-kernel - Re: [PATCH 5/8] mm: simplify freeing of devmap managed pages

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Message-ID: <01ae1d08-33ba-c38e-07ba-40721b95ed5c@nvidia.com>
Date:   Tue, 8 Feb 2022 07:50:38 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>
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>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "nvdimm@...ts.linux.dev" <nvdimm@...ts.linux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 5/8] mm: simplify freeing of devmap managed pages

> -static inline bool page_is_devmap_managed(struct page *page)
> +bool __put_devmap_managed_page(struct page *page);
> +static inline bool put_devmap_managed_page(struct page *page)
>   {
>   	if (!static_branch_unlikely(&devmap_managed_key))
>   		return false;
>   	if (!is_zone_device_page(page))
>   		return false;
> -	switch (page->pgmap->type) {
> -	case MEMORY_DEVICE_PRIVATE:
> -	case MEMORY_DEVICE_FS_DAX:
> -		return true;
> -	default:
> -		break;
> -	}

nit:- how some variant of following to makes all cases evident
without having to look into memremap.h for other enum values ?

         switch (page->pgmap->type) {
         case MEMORY_DEVICE_PRIVATE:
         case MEMORY_DEVICE_FS_DAX:
                 return __put_devmap_managed_page(page);
         case MEMORY_DEVICE_GENERIC:
         case MEMORY_DEVICE_PCI_P2PDMA:
                 return false;
         default:
                 WARN_ON_ONCE(1);
                 return false;
         }


> -	return false;
> +	if (page->pgmap->type != MEMORY_DEVICE_PRIVATE &&
> +	    page->pgmap->type != MEMORY_DEVICE_FS_DAX)
> +		return false;
> +	return __put_devmap_managed_page(page);

nit:- we are only returning true value from __put_devmap_managed_page()
in this patch. Perhaps make it __put_dev_map_managed_page()
return void and return true from above ?

or maybe someone can send a cleanup once this is merged.

>   }
>   

Irrespective of above comment(s), looks good.

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>