Re: [PATCH v2 2/7] drm/ttm/pool: Fix ttm_pool_alloc error path

[Christian König <christian.koenig@xxxxxxx>]

Am 07.03.23 um 15:46 schrieb Thomas Hellström:
> When hitting an error, the error path forgot to unmap dma mappings and
> could call set_pages_wb() on already uncached pages.
>
> Fix this by introducing a common __ttm_pool_free() function that
> does the right thing.
>
> v2:
> - Simplify __ttm_pool_free() (Christian König)
>
> Fixes: d099fc8f540a ("drm/ttm: new TT backend allocation pool v3")
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> Cc: Christian Koenig <christian.koenig@xxxxxxx>
> Cc: Huang Rui <ray.huang@xxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> ---
>   drivers/gpu/drm/ttm/ttm_pool.c | 68 +++++++++++++++++++---------------
>   1 file changed, 38 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index aa116a7bbae3..0b6e20613d19 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -367,6 +367,30 @@ static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
>   	return 0;
>   }
>   
> +static void __ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt,

Maybe name that ttm_pool_free_range() and add a comment why we need it. 
Something like "/* Cleanup all pages in the tt between start_page till 
end_page */".

Apart from that looks good to me.

Regards,
Christian.

> +			    enum ttm_caching caching,
> +			    pgoff_t start_page, pgoff_t end_page)
> +{
> +	struct page **pages = tt->pages;
> +	unsigned int order;
> +	pgoff_t i, nr;
> +
> +	for (i = start_page; i < end_page; i += nr, pages += nr) {
> +		struct ttm_pool_type *pt = NULL;
> +
> +		order = ttm_pool_page_order(pool, *pages);
> +		nr = (1UL << order);
> +		if (tt->dma_address)
> +			ttm_pool_unmap(pool, tt->dma_address[i], nr);
> +
> +		pt = ttm_pool_select_type(pool, caching, order);
> +		if (pt)
> +			ttm_pool_type_give(pt, *pages);
> +		else
> +			ttm_pool_free_page(pool, caching, order, *pages);
> +	}
> +}
> +
>   /**
>    * ttm_pool_alloc - Fill a ttm_tt object
>    *
> @@ -382,12 +406,14 @@ static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
>   int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   		   struct ttm_operation_ctx *ctx)
>   {
> -	unsigned long num_pages = tt->num_pages;
> +	pgoff_t num_pages = tt->num_pages;
>   	dma_addr_t *dma_addr = tt->dma_address;
>   	struct page **caching = tt->pages;
>   	struct page **pages = tt->pages;
> +	enum ttm_caching page_caching;
>   	gfp_t gfp_flags = GFP_USER;
> -	unsigned int i, order;
> +	pgoff_t caching_divide;
> +	unsigned int order;
>   	struct page *p;
>   	int r;
>   
> @@ -410,6 +436,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   	     order = min_t(unsigned int, order, __fls(num_pages))) {
>   		struct ttm_pool_type *pt;
>   
> +		page_caching = tt->caching;
>   		pt = ttm_pool_select_type(pool, tt->caching, order);
>   		p = pt ? ttm_pool_type_take(pt) : NULL;
>   		if (p) {
> @@ -418,6 +445,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   			if (r)
>   				goto error_free_page;
>   
> +			caching = pages;
>   			do {
>   				r = ttm_pool_page_allocated(pool, order, p,
>   							    &dma_addr,
> @@ -426,14 +454,15 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   				if (r)
>   					goto error_free_page;
>   
> +				caching = pages;
>   				if (num_pages < (1 << order))
>   					break;
>   
>   				p = ttm_pool_type_take(pt);
>   			} while (p);
> -			caching = pages;
>   		}
>   
> +		page_caching = ttm_cached;
>   		while (num_pages >= (1 << order) &&
>   		       (p = ttm_pool_alloc_page(pool, gfp_flags, order))) {
>   
> @@ -442,6 +471,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   							   tt->caching);
>   				if (r)
>   					goto error_free_page;
> +				caching = pages;
>   			}
>   			r = ttm_pool_page_allocated(pool, order, p, &dma_addr,
>   						    &num_pages, &pages);
> @@ -468,15 +498,13 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
>   	return 0;
>   
>   error_free_page:
> -	ttm_pool_free_page(pool, tt->caching, order, p);
> +	ttm_pool_free_page(pool, page_caching, order, p);
>   
>   error_free_all:
>   	num_pages = tt->num_pages - num_pages;
> -	for (i = 0; i < num_pages; ) {
> -		order = ttm_pool_page_order(pool, tt->pages[i]);
> -		ttm_pool_free_page(pool, tt->caching, order, tt->pages[i]);
> -		i += 1 << order;
> -	}
> +	caching_divide = caching - tt->pages;
> +	__ttm_pool_free(pool, tt, tt->caching, 0, caching_divide);
> +	__ttm_pool_free(pool, tt, ttm_cached, caching_divide, num_pages);
>   
>   	return r;
>   }
> @@ -492,27 +520,7 @@ EXPORT_SYMBOL(ttm_pool_alloc);
>    */
>   void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)
>   {
> -	unsigned int i;
> -
> -	for (i = 0; i < tt->num_pages; ) {
> -		struct page *p = tt->pages[i];
> -		unsigned int order, num_pages;
> -		struct ttm_pool_type *pt;
> -
> -		order = ttm_pool_page_order(pool, p);
> -		num_pages = 1ULL << order;
> -		if (tt->dma_address)
> -			ttm_pool_unmap(pool, tt->dma_address[i], num_pages);
> -
> -		pt = ttm_pool_select_type(pool, tt->caching, order);
> -		if (pt)
> -			ttm_pool_type_give(pt, tt->pages[i]);
> -		else
> -			ttm_pool_free_page(pool, tt->caching, order,
> -					   tt->pages[i]);
> -
> -		i += num_pages;
> -	}
> +	__ttm_pool_free(pool, tt, tt->caching, 0, tt->num_pages);
>   
>   	while (atomic_long_read(&allocated_pages) > page_pool_size)
>   		ttm_pool_shrink();