On Sat, Apr 10, 2021 at 12:37:58AM +0200, Matteo Croce wrote:
> This is needed by the page_pool to avoid recycling a page not allocated
> via page_pool.
Is the PageType mechanism more appropriate to your needs? It wouldn't
be if you use page->_mapcount (ie mapping it to userspace).
> Signed-off-by: Matteo Croce <mcroce@xxxxxxxxxxxxx>
> ---
> include/linux/mm_types.h | 1 +
> include/net/page_pool.h | 2 ++
> net/core/page_pool.c | 4 ++++
> 3 files changed, 7 insertions(+)
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 6613b26a8894..ef2d0d5f62e4 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -101,6 +101,7 @@ struct page {
> * 32-bit architectures.
> */
> dma_addr_t dma_addr;
> + unsigned long signature;
> };
> struct { /* slab, slob and slub */
> union {
> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index b5b195305346..b30405e84b5e 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -63,6 +63,8 @@
> */
> #define PP_ALLOC_CACHE_SIZE 128
> #define PP_ALLOC_CACHE_REFILL 64
> +#define PP_SIGNATURE 0x20210303
> +
> struct pp_alloc_cache {
> u32 count;
> void *cache[PP_ALLOC_CACHE_SIZE];
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index ad8b0707af04..2ae9b554ef98 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -232,6 +232,8 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
> page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
>
> skip_dma_map:
> + page->signature = PP_SIGNATURE;
> +
> /* Track how many pages are held 'in-flight' */
> pool->pages_state_hold_cnt++;
>
> @@ -302,6 +304,8 @@ void page_pool_release_page(struct page_pool *pool, struct page *page)
> DMA_ATTR_SKIP_CPU_SYNC);
> page->dma_addr = 0;
> skip_dma_unmap:
> + page->signature = 0;
> +
> /* This may be the last page returned, releasing the pool, so
> * it is not safe to reference pool afterwards.
> */
> --
> 2.30.2
>
