Use clear_pages() and clear_highpage() properly in the DMA heap allocator.
Signed-off-by: Linus Walleij linusw@kernel.org --- Changes in v2: - Added a second patch to use the clear_highpage() helper. - Link to v1: https://lore.kernel.org/r/20260304-cma-heap-clear-pages-v1-1-6ff59da716d3@ke...
--- Linus Walleij (2): dma-buf: heaps: Clear CMA pages with clear_pages() dma-buf: heaps: Clear CMA highages using helper
drivers/dma-buf/heaps/cma_heap.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f change-id: 20260303-cma-heap-clear-pages-540f3ac9f734
Best regards,
As of commit 62a9f5a85b98 "mm: introduce clear_pages() and clear_user_pages()" we can clear a range of pages with a potentially assembly-optimized call.
Instead of using a memset, use this helper to clear the whole range of pages from the CMA allocation.
Signed-off-by: Linus Walleij linusw@kernel.org --- drivers/dma-buf/heaps/cma_heap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index bd3370b9a3f6..f0bacf25ed9d 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -343,7 +343,7 @@ static struct dma_buf *cma_heap_allocate(struct dma_heap *heap, nr_clear_pages--; } } else { - memset(page_address(cma_pages), 0, size); + clear_pages(page_address(cma_pages), pagecount); }
buffer->pages = kmalloc_objs(*buffer->pages, pagecount);
On Tue, Mar 10, 2026 at 1:53 AM Linus Walleij linusw@kernel.org wrote:
As of commit 62a9f5a85b98 "mm: introduce clear_pages() and clear_user_pages()" we can clear a range of pages with a potentially assembly-optimized call.
Instead of using a memset, use this helper to clear the whole range of pages from the CMA allocation.
Signed-off-by: Linus Walleij linusw@kernel.org
Reviewed-by: T.J. Mercier tjmercier@google.com
Currently the CMA allocator clears highmem pages using kmap()->clear_page()->kunmap(), but there is a helper static inline in <linux/highmem.h> that does the same for us so use clear_highpage() instead of open coding this.
Suggested-by: T.J. Mercier tjmercier@google.com Signed-off-by: Linus Walleij linusw@kernel.org --- drivers/dma-buf/heaps/cma_heap.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index f0bacf25ed9d..92865786cfc9 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -329,10 +329,7 @@ static struct dma_buf *cma_heap_allocate(struct dma_heap *heap, struct page *page = cma_pages;
while (nr_clear_pages > 0) { - void *vaddr = kmap_local_page(page); - - clear_page(vaddr); - kunmap_local(vaddr); + clear_highpage(page); /* * Avoid wasting time zeroing memory if the process * has been killed by SIGKILL.
On 3/10/26 09:53, Linus Walleij wrote:
Currently the CMA allocator clears highmem pages using kmap()->clear_page()->kunmap(), but there is a helper static inline in <linux/highmem.h> that does the same for us so use clear_highpage() instead of open coding this.
Suggested-by: T.J. Mercier tjmercier@google.com Signed-off-by: Linus Walleij linusw@kernel.org
Ah yes, somebody pointed that out to me before but I never found time to write a patch to clean it up.
Reviewed-by: Christian König christian.koenig@amd.com
drivers/dma-buf/heaps/cma_heap.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index f0bacf25ed9d..92865786cfc9 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -329,10 +329,7 @@ static struct dma_buf *cma_heap_allocate(struct dma_heap *heap, struct page *page = cma_pages;
while (nr_clear_pages > 0) {
void *vaddr = kmap_local_page(page);clear_page(vaddr);kunmap_local(vaddr);
clear_highpage(page); /* * Avoid wasting time zeroing memory if the process * has been killed by SIGKILL.-- 2.53.0
On Tue, Mar 10, 2026 at 1:53 AM Linus Walleij linusw@kernel.org wrote:
Currently the CMA allocator clears highmem pages using kmap()->clear_page()->kunmap(), but there is a helper static inline in <linux/highmem.h> that does the same for us so use clear_highpage() instead of open coding this.
Suggested-by: T.J. Mercier tjmercier@google.com Signed-off-by: Linus Walleij linusw@kernel.org
Reviewed-by: T.J. Mercier tjmercier@google.com
Thanks!
On Tue, 10 Mar 2026 09:53:10 +0100, Linus Walleij wrote:
Use clear_pages() and clear_highpage() properly in the DMA heap allocator.
Signed-off-by: Linus Walleij linusw@kernel.org
Reviewed-by: Maxime Ripard mripard@kernel.org
Thanks! Maxime
On Tue, Mar 10, 2026 at 9:53 AM Linus Walleij linusw@kernel.org wrote:
Use clear_pages() and clear_highpage() properly in the DMA heap allocator.
Signed-off-by: Linus Walleij linusw@kernel.org
Patches pushed to drm-misc-next!
Yours, Linus Walleij
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