On Fri, Jul 17, 2026 at 11:34:19PM +0530, Aneesh Kumar K.V (Arm) wrote:
> Commit 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool
> helper") changed dma_direct_alloc_from_pool() to return the CPU address
> from dma_alloc_from_pool(). That fits dma_direct_alloc(), but
> dma_direct_alloc_pages() also uses the helper and expects a struct page *.
>
> Fix this by making dma_direct_alloc_from_pool() return the struct page *
> again, and pass the CPU address back through an out-parameter for the
> dma_direct_alloc() caller.
>
> Fixes: 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool
> helper")
> Cc: [email protected]
> Tested-by: Michael Kelley <[email protected]>
> Tested-by: Mostafa Saleh <[email protected]>
> Reviewed-by: Jason Gunthorpe <[email protected]>
> Signed-off-by: Aneesh Kumar K.V (Arm) <[email protected]>
> ---
> kernel/dma/direct.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index d8219efe3273..363d984d90e7 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -164,22 +164,21 @@ static bool dma_direct_use_pool(struct device *dev,
> gfp_t gfp)
> return !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev);
> }
>
> -static void *dma_direct_alloc_from_pool(struct device *dev, size_t size,
> - dma_addr_t *dma_handle, gfp_t gfp)
> +static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t
> size,
> + dma_addr_t *dma_handle, void **cpu_addr, gfp_t gfp)
> {
> struct page *page;
> u64 phys_limit;
> - void *ret;
>
> if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_DMA_COHERENT_POOL)))
> return NULL;
>
> gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit);
> - page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok);
> + page = dma_alloc_from_pool(dev, size, cpu_addr, gfp, dma_coherent_ok);
> if (!page)
> return NULL;
> *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
> - return ret;
> + return page;
> }
>
> static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
> @@ -247,8 +246,11 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> * the atomic pools instead if we aren't allowed block.
> */
> if ((remap || force_dma_unencrypted(dev)) &&
> - dma_direct_use_pool(dev, gfp))
> - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
> + dma_direct_use_pool(dev, gfp)) {
> + page = dma_direct_alloc_from_pool(dev, size, dma_handle,
> + &ret, gfp);
> + return page ? ret : NULL;
Sorry for joining the discussion late, but the line above caught my
attention.
Why do we need both ret and page? We can derive cpu_addr from page and
vice versa. Do we really need the &ret parameter? Or, more generally, do
we really need "struct page *"?
static struct page *__dma_alloc_from_pool(struct device *dev, size_t size,
struct gen_pool *pool, void **cpu_addr,
bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t))
{
...
*cpu_addr = (void *)addr;
memset(*cpu_addr, 0, size);
return pfn_to_page(__phys_to_pfn(phys));
}
Why
> + }
>
> /* we always manually zero the memory once we are done */
> page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true);
> @@ -357,7 +359,7 @@ struct page *dma_direct_alloc_pages(struct device *dev,
> size_t size,
> void *ret;
>
> if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
> - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
> + return dma_direct_alloc_from_pool(dev, size, dma_handle, &ret,
> gfp);
>
> page = __dma_direct_alloc_pages(dev, size, gfp, false);
> if (!page)
> --
> 2.43.0
>
>
