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Subject: Re: [PATCH 02/10] drm/ttm: separate PageHighMem() and
 PageHighMemZone() use case
To:     js1304@gmail.com, Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Vlastimil Babka <vbabka@suse.cz>,
        Laura Abbott <labbott@redhat.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Michal Hocko <mhocko@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, Minchan Kim <minchan@kernel.org>,
        Rik van Riel <riel@surriel.com>,
        Huang Rui <ray.huang@amd.com>,
        Eric Biederman <ebiederm@xmission.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Pavel Machek <pavel@ucw.cz>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
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 <1587369582-3882-3-git-send-email-iamjoonsoo.kim@lge.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
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Am 20.04.20 um 09:59 schrieb js1304@gmail.com:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> Until now, PageHighMem() is used for two different cases. One is to check
> if there is a direct mapping for this page or not. The other is to check
> the zone of this page, that is, weather it is the highmem type zone or not.
>
> Now, we have separate functions, PageHighMem() and PageHighMemZone() for
> each cases. Use appropriate one.
>
> Note that there are some rules to determine the proper macro.
>
> 1. If PageHighMem() is called for checking if the direct mapping exists
> or not, use PageHighMem().
> 2. If PageHighMem() is used to predict the previous gfp_flags for
> this page, use PageHighMemZone(). The zone of the page is related to
> the gfp_flags.
> 3. If purpose of calling PageHighMem() is to count highmem page and
> to interact with the system by using this count, use PageHighMemZone().
> This counter is usually used to calculate the available memory for an
> kernel allocation and pages on the highmem zone cannot be available
> for an kernel allocation.
> 4. Otherwise, use PageHighMemZone(). It's safe since it's implementation
> is just copy of the previous PageHighMem() implementation and won't
> be changed.
>
> I apply the rule #4 for this patch.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Christian König <christian.koenig@amd.com> for the TTM 
changes, but I can't judge if the general approach makes sense or not.

Regards,
Christian.

> ---
>   drivers/gpu/drm/ttm/ttm_memory.c         | 4 ++--
>   drivers/gpu/drm/ttm/ttm_page_alloc.c     | 2 +-
>   drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 2 +-
>   drivers/gpu/drm/ttm/ttm_tt.c             | 2 +-
>   4 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_memory.c b/drivers/gpu/drm/ttm/ttm_memory.c
> index acd63b7..d071b71 100644
> --- a/drivers/gpu/drm/ttm/ttm_memory.c
> +++ b/drivers/gpu/drm/ttm/ttm_memory.c
> @@ -641,7 +641,7 @@ int ttm_mem_global_alloc_page(struct ttm_mem_global *glob,
>   	 */
>   
>   #ifdef CONFIG_HIGHMEM
> -	if (PageHighMem(page) && glob->zone_highmem != NULL)
> +	if (PageHighMemZone(page) && glob->zone_highmem != NULL)
>   		zone = glob->zone_highmem;
>   #else
>   	if (glob->zone_dma32 && page_to_pfn(page) > 0x00100000UL)
> @@ -656,7 +656,7 @@ void ttm_mem_global_free_page(struct ttm_mem_global *glob, struct page *page,
>   	struct ttm_mem_zone *zone = NULL;
>   
>   #ifdef CONFIG_HIGHMEM
> -	if (PageHighMem(page) && glob->zone_highmem != NULL)
> +	if (PageHighMemZone(page) && glob->zone_highmem != NULL)
>   		zone = glob->zone_highmem;
>   #else
>   	if (glob->zone_dma32 && page_to_pfn(page) > 0x00100000UL)
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
> index b40a467..847fabe 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
> @@ -530,7 +530,7 @@ static int ttm_alloc_new_pages(struct list_head *pages, gfp_t gfp_flags,
>   		/* gfp flags of highmem page should never be dma32 so we
>   		 * we should be fine in such case
>   		 */
> -		if (PageHighMem(p))
> +		if (PageHighMemZone(p))
>   			continue;
>   
>   #endif
> diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> index faefaae..338b2a2 100644
> --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
> @@ -747,7 +747,7 @@ static int ttm_dma_pool_alloc_new_pages(struct dma_pool *pool,
>   		/* gfp flags of highmem page should never be dma32 so we
>   		 * we should be fine in such case
>   		 */
> -		if (PageHighMem(p))
> +		if (PageHighMemZone(p))
>   			continue;
>   #endif
>   
> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
> index 2ec448e..6e094dd 100644
> --- a/drivers/gpu/drm/ttm/ttm_tt.c
> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
> @@ -119,7 +119,7 @@ static int ttm_tt_set_page_caching(struct page *p,
>   {
>   	int ret = 0;
>   
> -	if (PageHighMem(p))
> +	if (PageHighMemZone(p))
>   		return 0;
>   
>   	if (c_old != tt_cached) {