On Fri, 16 Apr 2021 16:27:55 +0100
Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> On Thu, Apr 15, 2021 at 08:08:32PM +0200, Jesper Dangaard Brouer wrote:
> > See below patch. Where I swap32 the dma address to satisfy
> > page->compound having bit zero cleared. (It is the simplest fix I could
> > come up with).
>
> I think this is slightly simpler, and as a bonus code that assumes the
> old layout won't compile.
This is clever, I like it! When reading the code one just have to
remember 'unsigned long' size difference between 64-bit vs 32-bit.
And I assume compiler can optimize the sizeof check out then doable.
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 6613b26a8894..5aacc1c10a45 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -97,10 +97,10 @@ struct page {
> };
> struct { /* page_pool used by netstack */
> /**
> - * @dma_addr: might require a 64-bit value even on
> + * @dma_addr: might require a 64-bit value on
> * 32-bit architectures.
> */
> - dma_addr_t dma_addr;
> + unsigned long dma_addr[2];
> };
> struct { /* slab, slob and slub */
> union {
> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index b5b195305346..db7c7020746a 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -198,7 +198,17 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
>
> static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
> {
> - return page->dma_addr;
> + dma_addr_t ret = page->dma_addr[0];
> + if (sizeof(dma_addr_t) > sizeof(unsigned long))
> + ret |= (dma_addr_t)page->dma_addr[1] << 32;
> + return ret;
> +}
> +
> +static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
> +{
> + page->dma_addr[0] = addr;
> + if (sizeof(dma_addr_t) > sizeof(unsigned long))
> + page->dma_addr[1] = addr >> 32;
> }
>
> static inline bool is_page_pool_compiled_in(void)
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index ad8b0707af04..f014fd8c19a6 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -174,8 +174,10 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool,
> struct page *page,
> unsigned int dma_sync_size)
> {
> + dma_addr_t dma_addr = page_pool_get_dma_addr(page);
> +
> dma_sync_size = min(dma_sync_size, pool->p.max_len);
> - dma_sync_single_range_for_device(pool->p.dev, page->dma_addr,
> + dma_sync_single_range_for_device(pool->p.dev, dma_addr,
> pool->p.offset, dma_sync_size,
> pool->p.dma_dir);
> }
> @@ -226,7 +228,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
> put_page(page);
> return NULL;
> }
> - page->dma_addr = dma;
> + page_pool_set_dma_addr(page, dma);
>
> if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
> page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
> @@ -294,13 +296,13 @@ void page_pool_release_page(struct page_pool *pool, struct page *page)
> */
> goto skip_dma_unmap;
>
> - dma = page->dma_addr;
> + dma = page_pool_get_dma_addr(page);
>
> - /* When page is unmapped, it cannot be returned our pool */
> + /* When page is unmapped, it cannot be returned to our pool */
> dma_unmap_page_attrs(pool->p.dev, dma,
> PAGE_SIZE << pool->p.order, pool->p.dma_dir,
> DMA_ATTR_SKIP_CPU_SYNC);
> - page->dma_addr = 0;
> + page_pool_set_dma_addr(page, 0);
> skip_dma_unmap:
> /* This may be the last page returned, releasing the pool, so
> * it is not safe to reference pool afterwards.
>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
