diff mbox series

[RFC,v3,02/12] net: page_pool: create hooks for custom page providers

Message ID 20231106024413.2801438-3-almasrymina@google.com
State New
Headers
Series Device Memory TCP |

Commit Message

Mina Almasry Nov. 6, 2023, 2:44 a.m. UTC 
  From: Jakub Kicinski <kuba@kernel.org>

The page providers which try to reuse the same pages will
need to hold onto the ref, even if page gets released from
the pool - as in releasing the page from the pp just transfers
the "ownership" reference from pp to the provider, and provider
will wait for other references to be gone before feeding this
page back into the pool.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mina Almasry <almasrymina@google.com>


---

This is implemented by Jakub in his RFC:
https://lore.kernel.org/netdev/f8270765-a27b-6ccf-33ea-cda097168d79@redhat.com/T/

I take no credit for the idea or implementation; I only added minor
edits to make this workable with device memory TCP, and removed some
hacky test code. This is a critical dependency of device memory TCP
and thus I'm pulling it into this series to make it revewable and
mergable.

---
 include/net/page_pool/types.h | 18 +++++++++++++
 net/core/page_pool.c          | 51 +++++++++++++++++++++++++++++++----
 2 files changed, 64 insertions(+), 5 deletions(-)

Comments

Jakub Kicinski Nov. 13, 2023, 10:10 p.m. UTC | #1 
On Sun, 12 Nov 2023 19:28:52 -0800 Mina Almasry wrote:
> My issue with this is that if the driver doesn't support dmabuf then
> the driver will accidentally use the pp backed by the dmabuf, allocate
> a page from it, then call page_address() on it or something, and
> crash.
> 
> Currently I avoid that by having the driver be responsible for picking
> up the dmabuf from the netdev_rx_queue and giving it to the page pool.
> What would be the appropriate way to check for driver support in the
> netlink API? Perhaps adding something to ndo_features_check?

We need some form of capabilities. I was expecting to add that as part
of the queue API. Either a new field in struct net_device or in ndos.
I tend to put static driver caps of this nature into ops.
See for instance .supported_ring_params in ethtool ops.
diff mbox series

Patch

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 6fc5134095ed..d4bea053bb7e 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -60,6 +60,8 @@  struct page_pool_params {
 	int		nid;
 	struct device	*dev;
 	struct napi_struct *napi;
+	u8		memory_provider;
+	void            *mp_priv;
 	enum dma_data_direction dma_dir;
 	unsigned int	max_len;
 	unsigned int	offset;
@@ -118,6 +120,19 @@  struct page_pool_stats {
 };
 #endif
 
+struct mem_provider;
+
+enum pp_memory_provider_type {
+	__PP_MP_NONE, /* Use system allocator directly */
+};
+
+struct pp_memory_provider_ops {
+	int (*init)(struct page_pool *pool);
+	void (*destroy)(struct page_pool *pool);
+	struct page *(*alloc_pages)(struct page_pool *pool, gfp_t gfp);
+	bool (*release_page)(struct page_pool *pool, struct page *page);
+};
+
 struct page_pool {
 	struct page_pool_params p;
 
@@ -165,6 +180,9 @@  struct page_pool {
 	 */
 	struct ptr_ring ring;
 
+	const struct pp_memory_provider_ops *mp_ops;
+	void *mp_priv;
+
 #ifdef CONFIG_PAGE_POOL_STATS
 	/* recycle stats are per-cpu to avoid locking */
 	struct page_pool_recycle_stats __percpu *recycle_stats;
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 578b6f2eeb46..7ea1f4682479 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -23,6 +23,8 @@ 
 
 #include <trace/events/page_pool.h>
 
+static DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
+
 #define DEFER_TIME (msecs_to_jiffies(1000))
 #define DEFER_WARN_INTERVAL (60 * HZ)
 
@@ -172,6 +174,7 @@  static int page_pool_init(struct page_pool *pool,
 			  const struct page_pool_params *params)
 {
 	unsigned int ring_qsize = 1024; /* Default */
+	int err;
 
 	memcpy(&pool->p, params, sizeof(pool->p));
 
@@ -225,10 +228,34 @@  static int page_pool_init(struct page_pool *pool,
 	/* Driver calling page_pool_create() also call page_pool_destroy() */
 	refcount_set(&pool->user_cnt, 1);
 
+	switch (pool->p.memory_provider) {
+	case __PP_MP_NONE:
+		break;
+	default:
+		err = -EINVAL;
+		goto free_ptr_ring;
+	}
+
+	pool->mp_priv = pool->p.mp_priv;
+	if (pool->mp_ops) {
+		err = pool->mp_ops->init(pool);
+		if (err) {
+			pr_warn("%s() mem-provider init failed %d\n",
+				__func__, err);
+			goto free_ptr_ring;
+		}
+
+		static_branch_inc(&page_pool_mem_providers);
+	}
+
 	if (pool->p.flags & PP_FLAG_DMA_MAP)
 		get_device(pool->p.dev);
 
 	return 0;
+
+free_ptr_ring:
+	ptr_ring_cleanup(&pool->ring, NULL);
+	return err;
 }
 
 /**
@@ -490,7 +517,10 @@  struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
 		return page;
 
 	/* Slow-path: cache empty, do real allocation */
-	page = __page_pool_alloc_pages_slow(pool, gfp);
+	if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_ops)
+		page = pool->mp_ops->alloc_pages(pool, gfp);
+	else
+		page = __page_pool_alloc_pages_slow(pool, gfp);
 	return page;
 }
 EXPORT_SYMBOL(page_pool_alloc_pages);
@@ -542,10 +572,13 @@  void __page_pool_release_page_dma(struct page_pool *pool, struct page *page)
 void page_pool_return_page(struct page_pool *pool, struct page *page)
 {
 	int count;
+	bool put;
 
-	__page_pool_release_page_dma(pool, page);
-
-	page_pool_clear_pp_info(page);
+	put = true;
+	if (static_branch_unlikely(&page_pool_mem_providers) && pool->mp_ops)
+		put = pool->mp_ops->release_page(pool, page);
+	else
+		__page_pool_release_page_dma(pool, page);
 
 	/* This may be the last page returned, releasing the pool, so
 	 * it is not safe to reference pool afterwards.
@@ -553,7 +586,10 @@  void page_pool_return_page(struct page_pool *pool, struct page *page)
 	count = atomic_inc_return_relaxed(&pool->pages_state_release_cnt);
 	trace_page_pool_state_release(pool, page, count);
 
-	put_page(page);
+	if (put) {
+		page_pool_clear_pp_info(page);
+		put_page(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).
@@ -821,6 +857,11 @@  static void __page_pool_destroy(struct page_pool *pool)
 	if (pool->disconnect)
 		pool->disconnect(pool);
 
+	if (pool->mp_ops) {
+		pool->mp_ops->destroy(pool);
+		static_branch_dec(&page_pool_mem_providers);
+	}
+
 	ptr_ring_cleanup(&pool->ring, NULL);
 
 	if (pool->p.flags & PP_FLAG_DMA_MAP)