linux-kernel - Re: [PATCH 4/5] net: page_pool: refactor dma_map into own function page_pool_dma

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Date:   Tue, 2 Mar 2021 20:49:06 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-Net <netdev@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-NFS <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH 4/5] net: page_pool: refactor dma_map into own function
 page_pool_dma_map

Hi Mel,

Can you please CC me in future revisions. I almost missed that!

On Mon, Mar 01, 2021 at 04:11:59PM +0000, Mel Gorman wrote:
> From: Jesper Dangaard Brouer <brouer@...hat.com>
> 
> In preparation for next patch, move the dma mapping into its own
> function, as this will make it easier to follow the changes.
> 
> V2: make page_pool_dma_map return boolean (Ilias)
> 

[...]

>  static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
>  						 gfp_t _gfp)
>  {
> +	unsigned int pp_flags = pool->p.flags;
>  	struct page *page;
>  	gfp_t gfp = _gfp;
> -	dma_addr_t dma;
>  
>  	/* We could always set __GFP_COMP, and avoid this branch, as
>  	 * prep_new_page() can handle order-0 with __GFP_COMP.
> @@ -211,30 +234,14 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
>  	if (!page)
>  		return NULL;
>  
> -	if (!(pool->p.flags & PP_FLAG_DMA_MAP))
> -		goto skip_dma_map;
> -
> -	/* Setup DMA mapping: use 'struct page' area for storing DMA-addr
> -	 * since dma_addr_t can be either 32 or 64 bits and does not always fit
> -	 * into page private data (i.e 32bit cpu with 64bit DMA caps)
> -	 * This mapping is kept for lifetime of page, until leaving pool.
> -	 */
> -	dma = dma_map_page_attrs(pool->p.dev, page, 0,
> -				 (PAGE_SIZE << pool->p.order),
> -				 pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> -	if (dma_mapping_error(pool->p.dev, dma)) {
> +	if (pp_flags & PP_FLAG_DMA_MAP &&

Nit pick but can we have if ((pp_flags & PP_FLAG_DMA_MAP) && ...

> +	    unlikely(!page_pool_dma_map(pool, page))) {
>  		put_page(page);
>  		return NULL;
>  	}
> -	page->dma_addr = dma;
>  
> -	if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> -		page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
> -
> -skip_dma_map:
>  	/* Track how many pages are held 'in-flight' */
>  	pool->pages_state_hold_cnt++;
> -
>  	trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
>  
>  	/* When page just alloc'ed is should/must have refcnt 1. */
> -- 
> 2.26.2
> 

Otherwise 
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>