Re: [PATCH 03/12] dmaengine: reference counted unmap data

[Bartlomiej Zolnierkiewicz]

On Thursday 06 December 2012 10:25:26 Dan Williams wrote:
> hang a common 'unmap' object off of dma descriptors for the purpose of
> providing a unified unmapping interface.  The lifetime of a mapping may
> span multiple descriptors, so these unmap objects are reference counted
> by related descriptor.
> 
> Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
> Cc: Tomasz Figa <t.figa@xxxxxxxxxxx>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
> Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> Signed-off-by: Dan Williams <djbw@xxxxxx>
> ---
>  drivers/dma/dmaengine.c   |  157 ++++++++++++++++++++++++++++++++++++++++++---
>  include/linux/dmaengine.h |    3 +
>  2 files changed, 151 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index f3cadc6..00f0baf 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -62,6 +62,7 @@
>  #include <linux/rculist.h>
>  #include <linux/idr.h>
>  #include <linux/slab.h>
> +#include <linux/mempool.h>
>  
>  static DEFINE_MUTEX(dma_list_mutex);
>  static DEFINE_IDR(dma_idr);
> @@ -856,6 +857,131 @@ void dma_async_device_unregister(struct dma_device *device)
>  }
>  EXPORT_SYMBOL(dma_async_device_unregister);
>  
> +struct dmaengine_unmap_pool {
> +	struct kmem_cache *cache;
> +	const char *name;
> +	mempool_t *pool;
> +	size_t size;
> +};
> +
> +#define __UNMAP_POOL(x) { .size = x, .name = "dmaengine-unmap-" __stringify(x) }
> +static struct dmaengine_unmap_pool unmap_pool[] = {
> +	__UNMAP_POOL(2),
> +	#if IS_ENABLED(ASYNC_TX_DMA)
> +	__UNMAP_POOL(16),
> +	__UNMAP_POOL(128),
> +	__UNMAP_POOL(256),
> +	#endif
> +};
> +
> +static struct dmaengine_unmap_pool *__get_unmap_pool(int nr)
> +{
> +	int order = get_count_order(nr);
> +
> +	switch (order) {
> +	case 0 ... 1:
> +		return &unmap_pool[0];
> +	case 2 ... 4:
> +		return &unmap_pool[1];
> +	case 5 ... 7:
> +		return &unmap_pool[2];
> +	case 8:
> +		return &unmap_pool[3];
> +	default:
> +		BUG();
> +		return NULL;
> +	}
> +
> +}
> +
> +static void dmaengine_unmap(struct kref *kref)
> +{
> +	struct dmaengine_unmap_data *unmap = container_of(kref, typeof(*unmap), kref);
> +	struct device *dev = unmap->dev;
> +	int cnt, i;
> +
> +	cnt = unmap->to_cnt;
> +	for (i = 0; i < cnt; i++)
> +		dma_unmap_page(dev, unmap->addr[i], unmap->len,
> +			       DMA_TO_DEVICE);
> +	cnt += unmap->from_cnt;
> +	for (; i < cnt; i++)
> +		dma_unmap_page(dev, unmap->addr[i], unmap->len,
> +			       DMA_FROM_DEVICE);
> +	cnt += unmap->bidi_cnt;
> +	for (; i < cnt; i++)
> +		dma_unmap_page(dev, unmap->addr[i], unmap->len,
> +			       DMA_BIDIRECTIONAL);
> +	kmem_cache_free(__get_unmap_pool(cnt)->cache, unmap);

Shouldn't it call mempool_free() instead?

> +}
> +
> +void dmaengine_unmap_put(struct dmaengine_unmap_data *unmap)
> +{
> +	if (unmap)
> +		kref_put(&unmap->kref, dmaengine_unmap);
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_unmap_put);
> +
> +static void dmaengine_destroy_unmap_pool(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(unmap_pool); i++) {
> +		struct dmaengine_unmap_pool *p = &unmap_pool[i];
> +
> +		if (p->cache)
> +			kmem_cache_destroy(p->cache);
> +		p->cache = NULL;
> +		if (p->pool)
> +			mempool_destroy(p->pool);
> +		p->pool = NULL;
> +	}
> +}
> +
> +static int dmaengine_init_unmap_pool(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(unmap_pool); i++) {
> +		struct dmaengine_unmap_pool *p = &unmap_pool[i];
> +		size_t size;
> +
> +		size = sizeof(struct dmaengine_unmap_data) +
> +		       sizeof(dma_addr_t) * p->size;
> +
> +		p->cache = kmem_cache_create(p->name, size, 0,
> +					     SLAB_HWCACHE_ALIGN, NULL);
> +		if (!p->cache)
> +			break;
> +		p->pool = mempool_create_slab_pool(1, p->cache);
> +		if (!p->pool)
> +			break;
> +	}
> +
> +	if (i > ARRAY_SIZE(unmap_pool))
> +		return 0;
> +
> +	dmaengine_destroy_unmap_pool();
> +	return -ENOMEM;
> +}
> +
> +static struct dmaengine_unmap_data *
> +dmaengine_get_unmap_data(struct device *dev, int nr, gfp_t flags)
> +{
> +	struct dmaengine_unmap_data *unmap;
> +
> +	unmap = mempool_alloc(__get_unmap_pool(nr)->pool, flags);
> +	if (!unmap)
> +		return NULL;
> +	unmap->to_cnt = 0;
> +	unmap->from_cnt = 0;
> +	unmap->bidi_cnt = 0;

unmap->len is not initialized

> +	kref_init(&unmap->kref);
> +	unmap->dev = dev;
> +
> +	return unmap;
> +}
> +
>  /**
>   * dma_async_memcpy_pg_to_pg - offloaded copy from page to page
>   * @chan: DMA channel to offload copy to
> @@ -877,24 +1003,33 @@ dma_async_memcpy_pg_to_pg(struct dma_chan *chan, struct page *dest_pg,
>  {
>  	struct dma_device *dev = chan->device;
>  	struct dma_async_tx_descriptor *tx;
> -	dma_addr_t dma_dest, dma_src;
> +	struct dmaengine_unmap_data *unmap;
>  	dma_cookie_t cookie;
>  	unsigned long flags;
>  
> -	dma_src = dma_map_page(dev->dev, src_pg, src_off, len, DMA_TO_DEVICE);
> -	dma_dest = dma_map_page(dev->dev, dest_pg, dest_off, len,
> -				DMA_FROM_DEVICE);
> -	flags = DMA_CTRL_ACK;
> -	tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, flags);
> +	unmap = dmaengine_get_unmap_data(dev->dev, 2, GFP_NOIO);
> +	if (!unmap)
> +		return -ENOMEM;
> +
> +	unmap->to_cnt = 1;
> +	unmap->from_cnt = 1;
> +	unmap->addr[0] = dma_map_page(dev->dev, src_pg, src_off, len,
> +				      DMA_TO_DEVICE);
> +	unmap->addr[1] = dma_map_page(dev->dev, dest_pg, dest_off, len,
> +				      DMA_FROM_DEVICE);

unmap->len is not set anywhere

> +	flags = DMA_CTRL_ACK | DMA_COMPL_SKIP_SRC_UNMAP |
> +		DMA_COMPL_SKIP_DEST_UNMAP;
> +	tx = dev->device_prep_dma_memcpy(chan, unmap->addr[1], unmap->addr[0],
> +					 len, flags);
>  
>  	if (!tx) {
> -		dma_unmap_page(dev->dev, dma_src, len, DMA_TO_DEVICE);
> -		dma_unmap_page(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
> +		dmaengine_unmap_put(unmap);
>  		return -ENOMEM;
>  	}
>  
> -	tx->callback = NULL;
> +	dma_set_unmap(tx, unmap);
>  	cookie = tx->tx_submit(tx);
> +	dmaengine_unmap_put(unmap);
>  
>  	preempt_disable();
>  	__this_cpu_add(chan->local->bytes_transferred, len);

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung Poland R&D Center
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