[RFC v1 7/9] page_pool: add page allocation and free hooks.

[Jonathan Lemon <jonathan.lemon@xxxxxxxxx>]

In order to allow for user-allocated page backing, add hooks to the
page pool so pages can be obtained and released from a user-supplied
provider instead of the system page allocator.

skbs are marked with skb_mark_for_recycle() if they contain pages
belonging to a page pool, and page_put() will deliver the pages back
to the pool instead of freeing them to the system page allocator.

Signed-off-by: Jonathan Lemon <jonathan.lemon@xxxxxxxxx>
---
 include/net/page_pool.h |  6 ++++++
 net/core/page_pool.c    | 41 ++++++++++++++++++++++++++++++++++-------
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index 813c93499f20..85c8423f9a7e 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -82,6 +82,12 @@ struct page_pool_params {
 	unsigned int	offset;  /* DMA addr offset */
 	void (*init_callback)(struct page *page, void *arg);
 	void *init_arg;
+	struct page *(*alloc_pages)(void *arg, int nid, gfp_t gfp,
+				    unsigned int order);
+	unsigned long (*alloc_bulk)(void *arg, gfp_t gfp, int nid,
+				    unsigned long nr_pages,
+				    struct page **page_array);
+	void (*put_page)(void *arg, struct page *page);
 };
 
 #ifdef CONFIG_PAGE_POOL_STATS
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 9b203d8660e4..21c6ee97bc7f 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -342,19 +342,47 @@ static void page_pool_clear_pp_info(struct page *page)
 	page->pp = NULL;
 }
 
+/* hooks to either page provider or system page allocator */
+static void page_pool_mm_put_page(struct page_pool *pool, struct page *page)
+{
+	if (pool->p.put_page)
+		return pool->p.put_page(pool->p.init_arg, page);
+	put_page(page);
+}
+
+static unsigned long page_pool_mm_alloc_bulk(struct page_pool *pool,
+					     gfp_t gfp,
+					     unsigned long nr_pages)
+{
+	if (pool->p.alloc_bulk)
+		return pool->p.alloc_bulk(pool->p.init_arg, gfp,
+					  pool->p.nid, nr_pages,
+					  pool->alloc.cache);
+	return alloc_pages_bulk_array_node(gfp, pool->p.nid,
+					   nr_pages, pool->alloc.cache);
+}
+
+static struct page *page_pool_mm_alloc(struct page_pool *pool, gfp_t gfp)
+{
+	if (pool->p.alloc_pages)
+		return pool->p.alloc_pages(pool->p.init_arg, pool->p.nid,
+					   gfp, pool->p.order);
+	return alloc_pages_node(pool->p.nid, gfp, pool->p.order);
+}
+
 static struct page *__page_pool_alloc_page_order(struct page_pool *pool,
 						 gfp_t gfp)
 {
 	struct page *page;
 
 	gfp |= __GFP_COMP;
-	page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
+	page = page_pool_mm_alloc(pool, gfp);
 	if (unlikely(!page))
 		return NULL;
 
 	if ((pool->p.flags & PP_FLAG_DMA_MAP) &&
 	    unlikely(!page_pool_dma_map(pool, page))) {
-		put_page(page);
+		page_pool_mm_put_page(pool, page);
 		return NULL;
 	}
 
@@ -389,8 +417,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 	/* Mark empty alloc.cache slots "empty" for alloc_pages_bulk_array */
 	memset(&pool->alloc.cache, 0, sizeof(void *) * bulk);
 
-	nr_pages = alloc_pages_bulk_array_node(gfp, pool->p.nid, bulk,
-					       pool->alloc.cache);
+	nr_pages = page_pool_mm_alloc_bulk(pool, gfp, bulk);
 	if (unlikely(!nr_pages))
 		return NULL;
 
@@ -401,7 +428,7 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
 		page = pool->alloc.cache[i];
 		if ((pp_flags & PP_FLAG_DMA_MAP) &&
 		    unlikely(!page_pool_dma_map(pool, page))) {
-			put_page(page);
+			page_pool_mm_put_page(pool, page);
 			continue;
 		}
 
@@ -501,7 +528,7 @@ static void page_pool_return_page(struct page_pool *pool, struct page *page)
 {
 	page_pool_release_page(pool, page);
 
-	put_page(page);
+	page_pool_mm_put_page(pool, page);
 	/* An optimization would be to call __free_pages(page, pool->p.order)
 	 * knowing page is not part of page-cache (thus avoiding a
 	 * __page_cache_release() call).
@@ -593,7 +620,7 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
 	recycle_stat_inc(pool, released_refcnt);
 	/* Do not replace this with page_pool_return_page() */
 	page_pool_release_page(pool, page);
-	put_page(page);
+	page_pool_mm_put_page(pool, page);
 
 	return NULL;
 }
-- 
2.30.2