Re: [PATCH v8 01/23] dma-direct: return struct page from dma_direct_alloc_from_pool()
From: Leon Romanovsky <leon@kernel.org>
Date: 2026-07-21 11:55:01
Also in:
linux-arm-kernel, linux-coco, linux-iommu, linux-s390, lkml, stable
On Fri, Jul 17, 2026 at 11:34:19PM +0530, Aneesh Kumar K.V (Arm) wrote:
quoted hunk ↗ jump to hunk
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: stable@vger.kernel.org Tested-by: Michael Kelley <redacted> Tested-by: Mostafa Saleh <smostafa@google.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org> --- 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
quoted hunk ↗ jump to hunk
+ } /* 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