[PATCH net-next v6 0/6] introduce page_pool_alloc() related API

[PATCH net-next v6 0/6] introduce page_pool_alloc() related API

[Yunsheng Lin]

In [1] & [2] & [3], there are usecases for veth and virtio_net
to use frag support in page pool to reduce memory usage, and it
may request different frag size depending on the head/tail
room space for xdp_frame/shinfo and mtu/packet size. When the
requested frag size is large enough that a single page can not
be split into more than one frag, using frag support only have
performance penalty because of the extra frag count handling
for frag support.

So this patchset provides a page pool API for the driver to
allocate memory with least memory utilization and performance
penalty when it doesn't know the size of memory it need
beforehand.

1. https://patchwork.kernel.org/project/netdevbpf/patch/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/
2. https://patchwork.kernel.org/project/netdevbpf/patch/20230526054621.18371-3-liangchen.linux@gmail.com/
3. https://github.com/alobakin/linux/tree/iavf-pp-frag

V6: add a PP_FLAG_PAGE_SPLIT_IN_DRIVER flag to fail the page_pool
    creation for 32-bit arch with 64-bit DMA when driver tries to
    do the page splitting itself, adjust the requested size to
    include head/tail room in veth, and rebased on the latest
    next-net.

v5 RFC: add a new page_pool_cache_alloc() API, and other minor
        change as discussed in v4. As there seems to be three
        comsumers that might be made use of the new API, so
        repost it as RFC and CC the relevant authors to see
        if the new API fits their need.

V4. Fix a typo and add a patch to update document about frag
    API, PAGE_POOL_DMA_USE_PP_FRAG_COUNT is not renamed yet
    as we may need a different thread to discuss that.

V3: Incorporate changes from the disscusion with Alexander,
    mostly the inline wraper, PAGE_POOL_DMA_USE_PP_FRAG_COUNT
    change split to separate patch and comment change.
V2: Add patch to remove PP_FLAG_PAGE_FRAG flags and mention
    virtio_net usecase in the cover letter.
V1: Drop RFC tag and page_pool_frag patch.

Yunsheng Lin (6):
  page_pool: frag API support for 32-bit arch with 64-bit DMA
  page_pool: unify frag_count handling in page_pool_is_last_frag()
  page_pool: remove PP_FLAG_PAGE_FRAG
  page_pool: introduce page_pool[_cache]_alloc() API
  page_pool: update document about frag API
  net: veth: use newly added page pool API for veth with xdp

 Documentation/networking/page_pool.rst        |   4 +-
 drivers/net/ethernet/broadcom/bnxt/bnxt.c     |   2 -
 .../net/ethernet/hisilicon/hns3/hns3_enet.c   |   3 +-
 .../marvell/octeontx2/nic/otx2_common.c       |   2 +-
 .../net/ethernet/mellanox/mlx5/core/en_main.c |   3 +-
 drivers/net/veth.c                            |  24 +-
 drivers/net/wireless/mediatek/mt76/mac80211.c |   2 +-
 include/net/page_pool/helpers.h               | 210 ++++++++++++++++--
 include/net/page_pool/types.h                 |  38 ++--
 net/core/page_pool.c                          |  30 +--
 net/core/skbuff.c                             |   2 +-
 11 files changed, 251 insertions(+), 69 deletions(-)

-- 
2.33.0

[PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Yunsheng Lin]

Currently page_pool_alloc_frag() is not supported in 32-bit
arch with 64-bit DMA because of the overlap issue between
pp_frag_count and dma_addr_upper in 'struct page' for those
arches, which seems to be quite common, see [1], which means
driver may need to handle it when using frag API.

In order to simplify the driver's work when using frag API
this patch allows page_pool_alloc_frag() to call
page_pool_alloc_pages() to return pages for those arches.

Add a PP_FLAG_PAGE_SPLIT_IN_DRIVER flag in order to fail the
page_pool creation for 32-bit arch with 64-bit DMA when driver
tries to do the page splitting itself.

Note that it may aggravate truesize underestimate problem for
skb as there is no page splitting for those pages, if driver
need a accurate truesize, it may calculate that according to
frag size, page order and PAGE_POOL_DMA_USE_PP_FRAG_COUNT
being true or not. And we may provide a helper for that if it
turns out to be helpful.

1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@huawei.com/

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 .../net/ethernet/mellanox/mlx5/core/en_main.c |  3 +-
 include/net/page_pool/helpers.h               | 38 +++++++++++++++--
 include/net/page_pool/types.h                 | 42 ++++++++++++-------
 net/core/page_pool.c                          | 15 +++----
 4 files changed, 68 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index bc9d5a5bea01..ec9c5a8cbda6 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -834,7 +834,8 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
 		struct page_pool_params pp_params = { 0 };
 
 		pp_params.order     = 0;
-		pp_params.flags     = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | PP_FLAG_PAGE_FRAG;
+		pp_params.flags     = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV |
+					PP_FLAG_PAGE_SPLIT_IN_DRIVER;
 		pp_params.pool_size = pool_size;
 		pp_params.nid       = node;
 		pp_params.dev       = rq->pdev;
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 94231533a369..cb18de55f239 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -29,8 +29,12 @@
 #ifndef _NET_PAGE_POOL_HELPERS_H
 #define _NET_PAGE_POOL_HELPERS_H
 
+#include <linux/dma-mapping.h>
 #include <net/page_pool/types.h>
 
+#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT	\
+		(sizeof(dma_addr_t) > sizeof(unsigned long))
+
 #ifdef CONFIG_PAGE_POOL_STATS
 int page_pool_ethtool_stats_get_count(void);
 u8 *page_pool_ethtool_stats_get_strings(u8 *data);
@@ -73,6 +77,29 @@ static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
 	return page_pool_alloc_pages(pool, gfp);
 }
 
+static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
+						unsigned int *offset,
+						unsigned int size, gfp_t gfp)
+{
+	unsigned int max_size = PAGE_SIZE << pool->p.order;
+
+	size = ALIGN(size, dma_get_cache_alignment());
+
+	if (WARN_ON(size > max_size))
+		return NULL;
+
+	/* Don't allow page splitting and allocate one big frag
+	 * for 32-bit arch with 64-bit DMA, corresponding to
+	 * the checking in page_pool_is_last_frag().
+	 */
+	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) {
+		*offset = 0;
+		return page_pool_alloc_pages(pool, gfp);
+	}
+
+	return __page_pool_alloc_frag(pool, offset, size, gfp);
+}
+
 static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
 						    unsigned int *offset,
 						    unsigned int size)
@@ -134,8 +161,14 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
 static inline bool page_pool_is_last_frag(struct page_pool *pool,
 					  struct page *page)
 {
-	/* If fragments aren't enabled or count is 0 we were the last user */
+	/* We assume we are the last frag user that is still holding
+	 * on to the page if:
+	 * 1. Fragments aren't enabled.
+	 * 2. We are running in 32-bit arch with 64-bit DMA.
+	 * 3. page_pool_defrag_page() indicate we are the last user.
+	 */
 	return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
+	       PAGE_POOL_DMA_USE_PP_FRAG_COUNT ||
 	       (page_pool_defrag_page(page, 1) == 0);
 }
 
@@ -197,9 +230,6 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
 	page_pool_put_full_page(pool, page, true);
 }
 
-#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT	\
-		(sizeof(dma_addr_t) > sizeof(unsigned long))
-
 /**
  * page_pool_get_dma_addr() - Retrieve the stored DMA address.
  * @page:	page allocated from a page pool
diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 887e7946a597..079337c42aa6 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -6,21 +6,29 @@
 #include <linux/dma-direction.h>
 #include <linux/ptr_ring.h>
 
-#define PP_FLAG_DMA_MAP		BIT(0) /* Should page_pool do the DMA
-					* map/unmap
-					*/
-#define PP_FLAG_DMA_SYNC_DEV	BIT(1) /* If set all pages that the driver gets
-					* from page_pool will be
-					* DMA-synced-for-device according to
-					* the length provided by the device
-					* driver.
-					* Please note DMA-sync-for-CPU is still
-					* device driver responsibility
-					*/
-#define PP_FLAG_PAGE_FRAG	BIT(2) /* for page frag feature */
+/* Should page_pool do the DMA map/unmap */
+#define PP_FLAG_DMA_MAP			BIT(0)
+
+/* If set all pages that the driver gets from page_pool will be
+ * DMA-synced-for-device according to the length provided by the device driver.
+ * Please note DMA-sync-for-CPU is still device driver responsibility
+ */
+#define PP_FLAG_DMA_SYNC_DEV		BIT(1)
+
+/* for page frag feature */
+#define PP_FLAG_PAGE_FRAG		BIT(2)
+
+/* If set driver will do the page splitting itself. This is used to fail the
+ * page_pool creation because there is overlap issue between pp_frag_count and
+ * dma_addr_upper in 'struct page' for some arches with
+ * PAGE_POOL_DMA_USE_PP_FRAG_COUNT being true.
+ */
+#define PP_FLAG_PAGE_SPLIT_IN_DRIVER	BIT(3)
+
 #define PP_FLAG_ALL		(PP_FLAG_DMA_MAP |\
 				 PP_FLAG_DMA_SYNC_DEV |\
-				 PP_FLAG_PAGE_FRAG)
+				 PP_FLAG_PAGE_FRAG |\
+				 PP_FLAG_PAGE_SPLIT_IN_DRIVER)
 
 /*
  * Fast allocation side cache array/stack
@@ -45,7 +53,8 @@ struct pp_alloc_cache {
 
 /**
  * struct page_pool_params - page pool parameters
- * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG
+ * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG,
+ *		PP_FLAG_PAGE_SPLIT_IN_DRIVER
  * @order:	2^order pages on allocation
  * @pool_size:	size of the ptr_ring
  * @nid:	NUMA node id to allocate from pages from
@@ -183,8 +192,9 @@ struct page_pool {
 };
 
 struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
-struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset,
-				  unsigned int size, gfp_t gfp);
+struct page *__page_pool_alloc_frag(struct page_pool *pool,
+				    unsigned int *offset, unsigned int size,
+				    gfp_t gfp);
 struct page_pool *page_pool_create(const struct page_pool_params *params);
 
 struct xdp_mem_info;
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 77cb75e63aca..d62c11aaea9a 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -14,7 +14,6 @@
 #include <net/xdp.h>
 
 #include <linux/dma-direction.h>
-#include <linux/dma-mapping.h>
 #include <linux/page-flags.h>
 #include <linux/mm.h> /* for put_page() */
 #include <linux/poison.h>
@@ -212,7 +211,7 @@ static int page_pool_init(struct page_pool *pool,
 	}
 
 	if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT &&
-	    pool->p.flags & PP_FLAG_PAGE_FRAG)
+	    pool->p.flags & PP_FLAG_PAGE_SPLIT_IN_DRIVER)
 		return -EINVAL;
 
 #ifdef CONFIG_PAGE_POOL_STATS
@@ -737,18 +736,16 @@ static void page_pool_free_frag(struct page_pool *pool)
 	page_pool_return_page(pool, page);
 }
 
-struct page *page_pool_alloc_frag(struct page_pool *pool,
-				  unsigned int *offset,
-				  unsigned int size, gfp_t gfp)
+struct page *__page_pool_alloc_frag(struct page_pool *pool,
+				    unsigned int *offset,
+				    unsigned int size, gfp_t gfp)
 {
 	unsigned int max_size = PAGE_SIZE << pool->p.order;
 	struct page *page = pool->frag_page;
 
-	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
-		    size > max_size))
+	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG))
 		return NULL;
 
-	size = ALIGN(size, dma_get_cache_alignment());
 	*offset = pool->frag_offset;
 
 	if (page && *offset + size > max_size) {
@@ -781,7 +778,7 @@ struct page *page_pool_alloc_frag(struct page_pool *pool,
 	alloc_stat_inc(pool, fast);
 	return page;
 }
-EXPORT_SYMBOL(page_pool_alloc_frag);
+EXPORT_SYMBOL(__page_pool_alloc_frag);
 
 static void page_pool_empty_ring(struct page_pool *pool)
 {
-- 
2.33.0

[PATCH net-next v6 2/6] page_pool: unify frag_count handling in page_pool_is_last_frag()

[Yunsheng Lin]

Currently when page_pool_create() is called with
PP_FLAG_PAGE_FRAG flag, page_pool_alloc_pages() is only
allowed to be called under the below constraints:
1. page_pool_fragment_page() need to be called to setup
   page->pp_frag_count immediately.
2. page_pool_defrag_page() often need to be called to drain
   the page->pp_frag_count when there is no more user will
   be holding on to that page.

Those constraints exist in order to support a page to be
split into multi frags.

And those constraints have some overhead because of the
cache line dirtying/bouncing and atomic update.

Those constraints are unavoidable for case when we need a
page to be split into more than one frag, but there is also
case that we want to avoid the above constraints and their
overhead when a page can't be split as it can only hold a big
frag as requested by user, depending on different use cases:
use case 1: allocate page without page splitting.
use case 2: allocate page with page splitting.
use case 3: allocate page with or without page splitting
            depending on the frag size.

Currently page pool only provide page_pool_alloc_pages() and
page_pool_alloc_frag() API to enable the 1 & 2 separately,
so we can not use a combination of 1 & 2 to enable 3, it is
not possible yet because of the per page_pool flag
PP_FLAG_PAGE_FRAG.

So in order to allow allocating unsplit page without the
overhead of split page while still allow allocating split
page we need to remove the per page_pool flag in
page_pool_is_last_frag(), as best as I can think of, it seems
there are two methods as below:
1. Add per page flag/bit to indicate a page is split or
   not, which means we might need to update that flag/bit
   everytime the page is recycled, dirtying the cache line
   of 'struct page' for use case 1.
2. Unify the page->pp_frag_count handling for both split and
   unsplit page by assuming all pages in the page pool is split
   into a big frag initially.

As page pool already supports use case 1 without dirtying the
cache line of 'struct page' whenever a page is recyclable, we
need to support the above use case 3 with minimal overhead,
especially not adding any noticeable overhead for use case 1,
and we are already doing an optimization by not updating
pp_frag_count in page_pool_defrag_page() for the last frag
user, this patch chooses to unify the pp_frag_count handling
to support the above use case 3.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 include/net/page_pool/helpers.h | 54 +++++++++++++++++++++++----------
 net/core/page_pool.c            | 10 +++++-
 2 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index cb18de55f239..19e8ba056868 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -134,7 +134,8 @@ inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
  */
 static inline void page_pool_fragment_page(struct page *page, long nr)
 {
-	atomic_long_set(&page->pp_frag_count, nr);
+	if (!PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
+		atomic_long_set(&page->pp_frag_count, nr);
 }
 
 static inline long page_pool_defrag_page(struct page *page, long nr)
@@ -142,33 +143,54 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
 	long ret;
 
 	/* If nr == pp_frag_count then we have cleared all remaining
-	 * references to the page. No need to actually overwrite it, instead
-	 * we can leave this to be overwritten by the calling function.
+	 * references to the page:
+	 * 1. 'n == 1': no need to actually overwrite it.
+	 * 2. 'n != 1': overwrite it with one, which is the rare case
+	 *              for frag draining.
 	 *
-	 * The main advantage to doing this is that an atomic_read is
-	 * generally a much cheaper operation than an atomic update,
-	 * especially when dealing with a page that may be partitioned
-	 * into only 2 or 3 pieces.
+	 * The main advantage to doing this is that not only we avoid a
+	 * atomic update, as an atomic_read is generally a much cheaper
+	 * operation than an atomic update, especially when dealing with
+	 * a page that may be partitioned into only 2 or 3 pieces; but
+	 * also unify the frag and non-frag handling by ensuring all
+	 * pages have been split into one big frag initially, and only
+	 * overwrite it when the page is split into more than one frag.
 	 */
-	if (atomic_long_read(&page->pp_frag_count) == nr)
+	if (atomic_long_read(&page->pp_frag_count) == nr) {
+		/* As we have ensured nr is always one for constant case
+		 * using the BUILD_BUG_ON(), only need to handle the
+		 * non-constant case here for frag count draining, which
+		 * is a rare case.
+		 */
+		BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
+		if (!__builtin_constant_p(nr))
+			atomic_long_set(&page->pp_frag_count, 1);
+
 		return 0;
+	}
 
 	ret = atomic_long_sub_return(nr, &page->pp_frag_count);
 	WARN_ON(ret < 0);
+
+	/* We are the last user here too, reset frag count back to 1 to
+	 * ensure all pages have been split into one big frag initially,
+	 * this should be the rare case when the last two frag users call
+	 * page_pool_defrag_page() currently.
+	 */
+	if (unlikely(!ret))
+		atomic_long_set(&page->pp_frag_count, 1);
+
 	return ret;
 }
 
-static inline bool page_pool_is_last_frag(struct page_pool *pool,
-					  struct page *page)
+static inline bool page_pool_is_last_frag(struct page *page)
 {
 	/* We assume we are the last frag user that is still holding
 	 * on to the page if:
-	 * 1. Fragments aren't enabled.
-	 * 2. We are running in 32-bit arch with 64-bit DMA.
-	 * 3. page_pool_defrag_page() indicate we are the last user.
+	 * 1. We are running in 32-bit arch with 64-bit DMA.
+	 * 2. page_pool_defrag_page() indicate we are the last user.
 	 */
-	return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
-	       PAGE_POOL_DMA_USE_PP_FRAG_COUNT ||
+	return PAGE_POOL_DMA_USE_PP_FRAG_COUNT ||
 	       (page_pool_defrag_page(page, 1) == 0);
 }
 
@@ -194,7 +216,7 @@ static inline void page_pool_put_page(struct page_pool *pool,
 	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
 	 */
 #ifdef CONFIG_PAGE_POOL
-	if (!page_pool_is_last_frag(pool, page))
+	if (!page_pool_is_last_frag(page))
 		return;
 
 	page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index d62c11aaea9a..653263fb5c85 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -371,6 +371,14 @@ static void page_pool_set_pp_info(struct page_pool *pool,
 {
 	page->pp = pool;
 	page->pp_magic |= PP_SIGNATURE;
+
+	/* Ensuring all pages have been split into one big frag initially:
+	 * page_pool_set_pp_info() is only called once for every page when it
+	 * is allocated from the page allocator and page_pool_fragment_page()
+	 * is dirtying the same cache line as the page->pp_magic above, so
+	 * the overhead is negligible.
+	 */
+	page_pool_fragment_page(page, 1);
 	if (pool->p.init_callback)
 		pool->p.init_callback(page, pool->p.init_arg);
 }
@@ -667,7 +675,7 @@ void page_pool_put_page_bulk(struct page_pool *pool, void **data,
 		struct page *page = virt_to_head_page(data[i]);
 
 		/* It is not the last user for the page frag case */
-		if (!page_pool_is_last_frag(pool, page))
+		if (!page_pool_is_last_frag(page))
 			continue;
 
 		page = __page_pool_put_page(pool, page, -1, false);
-- 
2.33.0

[PATCH net-next v6 3/6] page_pool: remove PP_FLAG_PAGE_FRAG

[Yunsheng Lin]

PP_FLAG_PAGE_FRAG is not really needed after pp_frag_count
handling is unified and page_pool_alloc_frag() is supported
in 32-bit arch with 64-bit DMA, so remove it.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c                | 2 --
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c          | 3 +--
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c | 2 +-
 drivers/net/wireless/mediatek/mt76/mac80211.c            | 2 +-
 include/net/page_pool/types.h                            | 8 ++------
 net/core/page_pool.c                                     | 3 ---
 net/core/skbuff.c                                        | 2 +-
 7 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 7be917a8da48..60b699be0d9b 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -3249,8 +3249,6 @@ static int bnxt_alloc_rx_page_pool(struct bnxt *bp,
 	pp.napi = &rxr->bnapi->napi;
 	pp.dev = &bp->pdev->dev;
 	pp.dma_dir = DMA_BIDIRECTIONAL;
-	if (PAGE_SIZE > BNXT_RX_PAGE_SIZE)
-		pp.flags |= PP_FLAG_PAGE_FRAG;
 
 	rxr->page_pool = page_pool_create(&pp);
 	if (IS_ERR(rxr->page_pool)) {
diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index eac2d0573241..ff0c219365f1 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -4926,8 +4926,7 @@ static void hns3_put_ring_config(struct hns3_nic_priv *priv)
 static void hns3_alloc_page_pool(struct hns3_enet_ring *ring)
 {
 	struct page_pool_params pp_params = {
-		.flags = PP_FLAG_DMA_MAP | PP_FLAG_PAGE_FRAG |
-				PP_FLAG_DMA_SYNC_DEV,
+		.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
 		.order = hns3_page_order(ring),
 		.pool_size = ring->desc_num * hns3_buf_size(ring) /
 				(PAGE_SIZE << hns3_page_order(ring)),
diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
index dce3cea00032..edc6acebf369 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
@@ -1433,7 +1433,7 @@ int otx2_pool_init(struct otx2_nic *pfvf, u16 pool_id,
 		return 0;
 	}
 
-	pp_params.flags = PP_FLAG_PAGE_FRAG | PP_FLAG_DMA_MAP;
+	pp_params.flags = PP_FLAG_DMA_MAP;
 	pp_params.pool_size = numptrs;
 	pp_params.nid = NUMA_NO_NODE;
 	pp_params.dev = pfvf->dev;
diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
index d158320bc15d..fe7cc67b7ee2 100644
--- a/drivers/net/wireless/mediatek/mt76/mac80211.c
+++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
@@ -566,7 +566,7 @@ int mt76_create_page_pool(struct mt76_dev *dev, struct mt76_queue *q)
 {
 	struct page_pool_params pp_params = {
 		.order = 0,
-		.flags = PP_FLAG_PAGE_FRAG,
+		.flags = 0,
 		.nid = NUMA_NO_NODE,
 		.dev = dev->dma_dev,
 	};
diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 079337c42aa6..4775cf95edb7 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -15,19 +15,15 @@
  */
 #define PP_FLAG_DMA_SYNC_DEV		BIT(1)
 
-/* for page frag feature */
-#define PP_FLAG_PAGE_FRAG		BIT(2)
-
 /* If set driver will do the page splitting itself. This is used to fail the
  * page_pool creation because there is overlap issue between pp_frag_count and
  * dma_addr_upper in 'struct page' for some arches with
  * PAGE_POOL_DMA_USE_PP_FRAG_COUNT being true.
  */
-#define PP_FLAG_PAGE_SPLIT_IN_DRIVER	BIT(3)
+#define PP_FLAG_PAGE_SPLIT_IN_DRIVER	BIT(2)
 
 #define PP_FLAG_ALL		(PP_FLAG_DMA_MAP |\
 				 PP_FLAG_DMA_SYNC_DEV |\
-				 PP_FLAG_PAGE_FRAG |\
 				 PP_FLAG_PAGE_SPLIT_IN_DRIVER)
 
 /*
@@ -53,7 +49,7 @@ struct pp_alloc_cache {
 
 /**
  * struct page_pool_params - page pool parameters
- * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG,
+ * @flags:	PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV,
  *		PP_FLAG_PAGE_SPLIT_IN_DRIVER
  * @order:	2^order pages on allocation
  * @pool_size:	size of the ptr_ring
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 653263fb5c85..d3b8efe98d5e 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -751,9 +751,6 @@ struct page *__page_pool_alloc_frag(struct page_pool *pool,
 	unsigned int max_size = PAGE_SIZE << pool->p.order;
 	struct page *page = pool->frag_page;
 
-	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG))
-		return NULL;
-
 	*offset = pool->frag_offset;
 
 	if (page && *offset + size > max_size) {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 33fdf04d4334..4b90b6ed10b2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5709,7 +5709,7 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 	/* In general, avoid mixing page_pool and non-page_pool allocated
 	 * pages within the same SKB. Additionally avoid dealing with clones
 	 * with page_pool pages, in case the SKB is using page_pool fragment
-	 * references (PP_FLAG_PAGE_FRAG). Since we only take full page
+	 * references (page_pool_alloc_frag()). Since we only take full page
 	 * references for cloned SKBs at the moment that would result in
 	 * inconsistent reference counts.
 	 * In theory we could take full references if @from is cloned and
-- 
2.33.0

[PATCH net-next v6 4/6] page_pool: introduce page_pool[_cache]_alloc() API

[Yunsheng Lin]

Currently page pool supports the below use cases:
use case 1: allocate page without page splitting using
            page_pool_alloc_pages() API if the driver knows
            that the memory it need is always bigger than
            half of the page allocated from page pool.
use case 2: allocate page frag with page splitting using
            page_pool_alloc_frag() API if the driver knows
            that the memory it need is always smaller than
            or equal to the half of the page allocated from
            page pool.

There is emerging use case [1] & [2] that is a mix of the
above two case: the driver doesn't know the size of memory it
need beforehand, so the driver may use something like below to
allocate memory with least memory utilization and performance
penalty:

if (size << 1 > max_size)
	page = page_pool_alloc_pages();
else
	page = page_pool_alloc_frag();

To avoid the driver doing something like above, add the
page_pool[_cache]_alloc() API to support the above use case,
and update the true size of memory that is acctually allocated
by updating '*size' back to the driver in order to avoid
exacerbating truesize underestimate problem.

Rename page_pool_free() which is used in the destroy process to
__page_pool_destroy() to avoid confusion with the newly added
API.

1. https://lore.kernel.org/all/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/
2. https://lore.kernel.org/all/20230526054621.18371-3-liangchen.linux@gmail.com/

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 include/net/page_pool/helpers.h | 70 +++++++++++++++++++++++++++++++++
 net/core/page_pool.c            |  4 +-
 2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 19e8ba056868..b920224f6584 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -109,6 +109,70 @@ static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
 	return page_pool_alloc_frag(pool, offset, size, gfp);
 }
 
+static inline struct page *page_pool_alloc(struct page_pool *pool,
+					   unsigned int *offset,
+					   unsigned int *size, gfp_t gfp)
+{
+	unsigned int max_size = PAGE_SIZE << pool->p.order;
+	struct page *page;
+
+	*size = ALIGN(*size, dma_get_cache_alignment());
+
+	if (WARN_ON(*size > max_size))
+		return NULL;
+
+	if ((*size << 1) > max_size || PAGE_POOL_DMA_USE_PP_FRAG_COUNT) {
+		*size = max_size;
+		*offset = 0;
+		return page_pool_alloc_pages(pool, gfp);
+	}
+
+	page = __page_pool_alloc_frag(pool, offset, *size, gfp);
+	if (unlikely(!page))
+		return NULL;
+
+	/* There is very likely not enough space for another frag, so append the
+	 * remaining size to the current frag to avoid truesize underestimate
+	 * problem.
+	 */
+	if (pool->frag_offset + *size > max_size) {
+		*size = max_size - *offset;
+		pool->frag_offset = max_size;
+	}
+
+	return page;
+}
+
+static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
+					       unsigned int *offset,
+					       unsigned int *size)
+{
+	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
+
+	return page_pool_alloc(pool, offset, size, gfp);
+}
+
+static inline void *page_pool_cache_alloc(struct page_pool *pool,
+					  unsigned int *size, gfp_t gfp)
+{
+	unsigned int offset;
+	struct page *page;
+
+	page = page_pool_alloc(pool, &offset, size, gfp);
+	if (unlikely(!page))
+		return NULL;
+
+	return page_address(page) + offset;
+}
+
+static inline void *page_pool_dev_cache_alloc(struct page_pool *pool,
+					      unsigned int *size)
+{
+	gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);
+
+	return page_pool_cache_alloc(pool, size, gfp);
+}
+
 /**
  * page_pool_get_dma_dir() - Retrieve the stored DMA direction.
  * @pool:	pool from which page was allocated
@@ -252,6 +316,12 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
 	page_pool_put_full_page(pool, page, true);
 }
 
+static inline void page_pool_cache_free(struct page_pool *pool, void *data,
+					bool allow_direct)
+{
+	page_pool_put_page(pool, virt_to_head_page(data), -1, allow_direct);
+}
+
 /**
  * page_pool_get_dma_addr() - Retrieve the stored DMA address.
  * @page:	page allocated from a page pool
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index d3b8efe98d5e..6f970fc7a0a7 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -800,7 +800,7 @@ static void page_pool_empty_ring(struct page_pool *pool)
 	}
 }
 
-static void page_pool_free(struct page_pool *pool)
+static void __page_pool_destroy(struct page_pool *pool)
 {
 	if (pool->disconnect)
 		pool->disconnect(pool);
@@ -851,7 +851,7 @@ static int page_pool_release(struct page_pool *pool)
 	page_pool_scrub(pool);
 	inflight = page_pool_inflight(pool);
 	if (!inflight)
-		page_pool_free(pool);
+		__page_pool_destroy(pool);
 
 	return inflight;
 }
-- 
2.33.0

[PATCH net-next v6 5/6] page_pool: update document about frag API

[Yunsheng Lin]

As more drivers begin to use the frag API, update the
document about how to decide which API to use for the
driver author.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 Documentation/networking/page_pool.rst |  4 +-
 include/net/page_pool/helpers.h        | 58 +++++++++++++++++++++++---
 2 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/Documentation/networking/page_pool.rst b/Documentation/networking/page_pool.rst
index 215ebc92752c..0c0705994f51 100644
--- a/Documentation/networking/page_pool.rst
+++ b/Documentation/networking/page_pool.rst
@@ -58,7 +58,9 @@ a page will cause no race conditions is enough.
 
 .. kernel-doc:: include/net/page_pool/helpers.h
    :identifiers: page_pool_put_page page_pool_put_full_page
-		 page_pool_recycle_direct page_pool_dev_alloc_pages
+		 page_pool_recycle_direct page_pool_cache_free
+		 page_pool_dev_alloc_pages page_pool_dev_alloc_frag
+		 page_pool_dev_alloc page_pool_dev_cache_alloc
 		 page_pool_get_dma_addr page_pool_get_dma_dir
 
 .. kernel-doc:: net/core/page_pool.c
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index b920224f6584..0f1eaa2986f9 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -8,13 +8,28 @@
 /**
  * DOC: page_pool allocator
  *
- * The page_pool allocator is optimized for the XDP mode that
- * uses one frame per-page, but it can fallback on the
- * regular page allocator APIs.
+ * The page_pool allocator is optimized for recycling page or page frag used by
+ * skb packet and xdp frame.
  *
- * Basic use involves replacing alloc_pages() calls with the
- * page_pool_alloc_pages() call.  Drivers should use
- * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
+ * Basic use involves replacing napi_alloc_frag() and alloc_pages() calls with
+ * page_pool_cache_alloc() and page_pool_alloc(), which allocate memory with or
+ * without page splitting depending on the requested memory size.
+ *
+ * If the driver knows that it always requires full pages or its allocates are
+ * always smaller than half a page, it can use one of the more specific API
+ * calls:
+ *
+ * 1. page_pool_alloc_pages(): allocate memory without page splitting when
+ * driver knows that the memory it need is always bigger than half of the page
+ * allocated from page pool. There is no cache line dirtying for 'struct page'
+ * when a page is recycled back to the page pool.
+ *
+ * 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
+ * knows that the memory it need is always smaller than or equal to half of the
+ * page allocated from page pool. Page splitting enables memory saving and thus
+ * avoid TLB/cache miss for data access, but there also is some cost to
+ * implement page splitting, mainly some cache line dirtying/bouncing for
+ * 'struct page' and atomic operation for page->pp_frag_count.
  *
  * API keeps track of in-flight pages, in order to let API user know
  * when it is safe to free a page_pool object.  Thus, API users
@@ -100,6 +115,14 @@ static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
 	return __page_pool_alloc_frag(pool, offset, size, gfp);
 }
 
+/**
+ * page_pool_dev_alloc_frag() - allocate a page frag.
+ * @pool[in]	pool from which to allocate
+ * @offset[out]	offset to the allocated page
+ * @size[in]	requested size
+ *
+ * Get a page frag from the page allocator or page_pool caches.
+ */
 static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
 						    unsigned int *offset,
 						    unsigned int size)
@@ -143,6 +166,14 @@ static inline struct page *page_pool_alloc(struct page_pool *pool,
 	return page;
 }
 
+/**
+ * page_pool_dev_alloc() - allocate a page or a page frag.
+ * @pool[in]:		pool from which to allocate
+ * @offset[out]:	offset to the allocated page
+ * @size[in, out]:	in as the requested size, out as the allocated size
+ *
+ * Get a page or a page frag from the page allocator or page_pool caches.
+ */
 static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
 					       unsigned int *offset,
 					       unsigned int *size)
@@ -165,6 +196,13 @@ static inline void *page_pool_cache_alloc(struct page_pool *pool,
 	return page_address(page) + offset;
 }
 
+/**
+ * page_pool_dev_cache_alloc() - allocate a cache.
+ * @pool[in]:		pool from which to allocate
+ * @size[in, out]:	in as the requested size, out as the allocated size
+ *
+ * Get a cache from the page allocator or page_pool caches.
+ */
 static inline void *page_pool_dev_cache_alloc(struct page_pool *pool,
 					      unsigned int *size)
 {
@@ -316,6 +354,14 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
 	page_pool_put_full_page(pool, page, true);
 }
 
+/**
+ * page_pool_cache_free() - free a cache into the page_pool
+ * @pool[in]:		pool from which cache was allocated
+ * @data[in]:		cache to free
+ * @allow_direct[in]:	freed by the consumer, allow lockless caching
+ *
+ * Free a cache allocated from page_pool_dev_cache_alloc().
+ */
 static inline void page_pool_cache_free(struct page_pool *pool, void *data,
 					bool allow_direct)
 {
-- 
2.33.0

[PATCH net-next v6 6/6] net: veth: use newly added page pool API for veth with xdp

[Yunsheng Lin]

Use page_pool[_cache]_alloc() API to allocate memory with
least memory utilization and performance penalty.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 drivers/net/veth.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 953f6d8f8db0..aaef234be0d8 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -736,10 +736,11 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
 	if (skb_shared(skb) || skb_head_is_locked(skb) ||
 	    skb_shinfo(skb)->nr_frags ||
 	    skb_headroom(skb) < XDP_PACKET_HEADROOM) {
-		u32 size, len, max_head_size, off;
+		u32 size, len, max_head_size, off, truesize, page_offset;
 		struct sk_buff *nskb;
 		struct page *page;
 		int i, head_off;
+		void *data;
 
 		/* We need a private copy of the skb and data buffers since
 		 * the ebpf program can modify it. We segment the original skb
@@ -752,14 +753,17 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
 		if (skb->len > PAGE_SIZE * MAX_SKB_FRAGS + max_head_size)
 			goto drop;
 
+		size = min_t(u32, skb->len, max_head_size);
+		truesize = SKB_HEAD_ALIGN(size) + VETH_XDP_HEADROOM;
+
 		/* Allocate skb head */
-		page = page_pool_dev_alloc_pages(rq->page_pool);
-		if (!page)
+		data = page_pool_dev_cache_alloc(rq->page_pool, &truesize);
+		if (!data)
 			goto drop;
 
-		nskb = napi_build_skb(page_address(page), PAGE_SIZE);
+		nskb = napi_build_skb(data, truesize);
 		if (!nskb) {
-			page_pool_put_full_page(rq->page_pool, page, true);
+			page_pool_cache_free(rq->page_pool, data, true);
 			goto drop;
 		}
 
@@ -767,7 +771,6 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
 		skb_copy_header(nskb, skb);
 		skb_mark_for_recycle(nskb);
 
-		size = min_t(u32, skb->len, max_head_size);
 		if (skb_copy_bits(skb, 0, nskb->data, size)) {
 			consume_skb(nskb);
 			goto drop;
@@ -782,14 +785,17 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
 		len = skb->len - off;
 
 		for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) {
-			page = page_pool_dev_alloc_pages(rq->page_pool);
+			size = min_t(u32, len, PAGE_SIZE);
+			truesize = size;
+
+			page = page_pool_dev_alloc(rq->page_pool, &page_offset,
+						   &truesize);
 			if (!page) {
 				consume_skb(nskb);
 				goto drop;
 			}
 
-			size = min_t(u32, len, PAGE_SIZE);
-			skb_add_rx_frag(nskb, i, page, 0, size, PAGE_SIZE);
+			skb_add_rx_frag(nskb, i, page, page_offset, size, truesize);
 			if (skb_copy_bits(skb, off, page_address(page),
 					  size)) {
 				consume_skb(nskb);
-- 
2.33.0

Re: [PATCH net-next v6 5/6] page_pool: update document about frag API

[Randy Dunlap]

Hi--

On 8/14/23 05:56, Yunsheng Lin wrote:
> As more drivers begin to use the frag API, update the
> document about how to decide which API to use for the
> driver author.
> 
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> CC: Lorenzo Bianconi <lorenzo@kernel.org>
> CC: Alexander Duyck <alexander.duyck@gmail.com>
> CC: Liang Chen <liangchen.linux@gmail.com>
> CC: Alexander Lobakin <aleksander.lobakin@intel.com>
> ---
>   Documentation/networking/page_pool.rst |  4 +-
>   include/net/page_pool/helpers.h        | 58 +++++++++++++++++++++++---
>   2 files changed, 55 insertions(+), 7 deletions(-)
> 

> diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
> index b920224f6584..0f1eaa2986f9 100644
> --- a/include/net/page_pool/helpers.h
> +++ b/include/net/page_pool/helpers.h
> @@ -8,13 +8,28 @@
>   /**
>    * DOC: page_pool allocator
>    *
> - * The page_pool allocator is optimized for the XDP mode that
> - * uses one frame per-page, but it can fallback on the
> - * regular page allocator APIs.
> + * The page_pool allocator is optimized for recycling page or page frag used by
> + * skb packet and xdp frame.
>    *
> - * Basic use involves replacing alloc_pages() calls with the
> - * page_pool_alloc_pages() call.  Drivers should use
> - * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
> + * Basic use involves replacing napi_alloc_frag() and alloc_pages() calls with
> + * page_pool_cache_alloc() and page_pool_alloc(), which allocate memory with or
> + * without page splitting depending on the requested memory size.
> + *
> + * If the driver knows that it always requires full pages or its allocates are

                                                              allocations

> + * always smaller than half a page, it can use one of the more specific API
> + * calls:
> + *
> + * 1. page_pool_alloc_pages(): allocate memory without page splitting when
> + * driver knows that the memory it need is always bigger than half of the page
> + * allocated from page pool. There is no cache line dirtying for 'struct page'
> + * when a page is recycled back to the page pool.
> + *
> + * 2. page_pool_alloc_frag(): allocate memory with page splitting when driver
> + * knows that the memory it need is always smaller than or equal to half of the
> + * page allocated from page pool. Page splitting enables memory saving and thus
> + * avoid TLB/cache miss for data access, but there also is some cost to

       avoids

> + * implement page splitting, mainly some cache line dirtying/bouncing for
> + * 'struct page' and atomic operation for page->pp_frag_count.
>    *
>    * API keeps track of in-flight pages, in order to let API user know
>    * when it is safe to free a page_pool object.  Thus, API users
> @@ -100,6 +115,14 @@ static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
>   	return __page_pool_alloc_frag(pool, offset, size, gfp);
>   }
>   
> +/**
> + * page_pool_dev_alloc_frag() - allocate a page frag.
> + * @pool[in]	pool from which to allocate
> + * @offset[out]	offset to the allocated page
> + * @size[in]	requested size

Please use kernel-doc syntax/notation here.

> + *
> + * Get a page frag from the page allocator or page_pool caches.
> + */
>   static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
>   						    unsigned int *offset,
>   						    unsigned int size)
> @@ -143,6 +166,14 @@ static inline struct page *page_pool_alloc(struct page_pool *pool,
>   	return page;
>   }
>   
> +/**
> + * page_pool_dev_alloc() - allocate a page or a page frag.
> + * @pool[in]:		pool from which to allocate
> + * @offset[out]:	offset to the allocated page
> + * @size[in, out]:	in as the requested size, out as the allocated size

and here.

> + *
> + * Get a page or a page frag from the page allocator or page_pool caches.
> + */
>   static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
>   					       unsigned int *offset,
>   					       unsigned int *size)
> @@ -165,6 +196,13 @@ static inline void *page_pool_cache_alloc(struct page_pool *pool,
>   	return page_address(page) + offset;
>   }
>   
> +/**
> + * page_pool_dev_cache_alloc() - allocate a cache.
> + * @pool[in]:		pool from which to allocate
> + * @size[in, out]:	in as the requested size, out as the allocated size

and here.

> + *
> + * Get a cache from the page allocator or page_pool caches.
> + */
>   static inline void *page_pool_dev_cache_alloc(struct page_pool *pool,
>   					      unsigned int *size)
>   {
> @@ -316,6 +354,14 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
>   	page_pool_put_full_page(pool, page, true);
>   }
>   
> +/**
> + * page_pool_cache_free() - free a cache into the page_pool
> + * @pool[in]:		pool from which cache was allocated
> + * @data[in]:		cache to free
> + * @allow_direct[in]:	freed by the consumer, allow lockless caching

and here.

> + *
> + * Free a cache allocated from page_pool_dev_cache_alloc().
> + */
>   static inline void page_pool_cache_free(struct page_pool *pool, void *data,
>   					bool allow_direct)
>   {

Thanks.

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Simon Horman]

On Mon, Aug 14, 2023 at 08:56:38PM +0800, Yunsheng Lin wrote:

...

> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 77cb75e63aca..d62c11aaea9a 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c

...

> @@ -737,18 +736,16 @@ static void page_pool_free_frag(struct page_pool *pool)
>  	page_pool_return_page(pool, page);
>  }
>  
> -struct page *page_pool_alloc_frag(struct page_pool *pool,
> -				  unsigned int *offset,
> -				  unsigned int size, gfp_t gfp)
> +struct page *__page_pool_alloc_frag(struct page_pool *pool,
> +				    unsigned int *offset,
> +				    unsigned int size, gfp_t gfp)
>  {
>  	unsigned int max_size = PAGE_SIZE << pool->p.order;
>  	struct page *page = pool->frag_page;
>  
> -	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
> -		    size > max_size))
> +	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG))

Hi Yunsheng Lin,

There is a ')' missing on the line above, which results in a build failure.

>  		return NULL;
>  
> -	size = ALIGN(size, dma_get_cache_alignment());
>  	*offset = pool->frag_offset;
>  
>  	if (page && *offset + size > max_size) {
> @@ -781,7 +778,7 @@ struct page *page_pool_alloc_frag(struct page_pool *pool,
>  	alloc_stat_inc(pool, fast);
>  	return page;
>  }
> -EXPORT_SYMBOL(page_pool_alloc_frag);
> +EXPORT_SYMBOL(__page_pool_alloc_frag);
>  
>  static void page_pool_empty_ring(struct page_pool *pool)
>  {

-- 
pw-bot: changes-requested

Re: [PATCH net-next v6 5/6] page_pool: update document about frag API

[Yunsheng Lin]

On 2023/8/15 6:42, Randy Dunlap wrote:
> Hi--

Thanks for the reviewing.

> 

...

>> @@ -100,6 +115,14 @@ static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
>>       return __page_pool_alloc_frag(pool, offset, size, gfp);
>>   }
>>   +/**
>> + * page_pool_dev_alloc_frag() - allocate a page frag.
>> + * @pool[in]    pool from which to allocate
>> + * @offset[out]    offset to the allocated page
>> + * @size[in]    requested size
> 
> Please use kernel-doc syntax/notation here.

Will change to:

/**
 * page_pool_dev_alloc_frag() - allocate a page frag.
 * @pool: pool from which to allocate
 * @offset: offset to the allocated page
 * @size: requested size
 *
 * Get a page frag from the page allocator or page_pool caches.
 *
 * Return:
 * Returns allocated page frag, otherwise return NULL.
 */


> 
>> + *
>> + * Get a page frag from the page allocator or page_pool caches.
>> + */
>>   static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
>>                               unsigned int *offset,
>>                               unsigned int size)
>> @@ -143,6 +166,14 @@ static inline struct page *page_pool_alloc(struct page_pool *pool,
>>       return page;
>>   }
>>   +/**
>> + * page_pool_dev_alloc() - allocate a page or a page frag.
>> + * @pool[in]:        pool from which to allocate
>> + * @offset[out]:    offset to the allocated page
>> + * @size[in, out]:    in as the requested size, out as the allocated size
> 
> and here.

/**
 * page_pool_dev_alloc() - allocate a page or a page frag.
 * @pool: pool from which to allocate
 * @offset: offset to the allocated page
 * @size: in as the requested size, out as the allocated size
 *
 * Get a page or a page frag from the page allocator or page_pool caches.
 *
 * Return:
 * Returns a page or a page frag, otherwise return NULL.
 */

> 
>> + *
>> + * Get a page or a page frag from the page allocator or page_pool caches.
>> + */
>>   static inline struct page *page_pool_dev_alloc(struct page_pool *pool,
>>                              unsigned int *offset,
>>                              unsigned int *size)
>> @@ -165,6 +196,13 @@ static inline void *page_pool_cache_alloc(struct page_pool *pool,
>>       return page_address(page) + offset;
>>   }
>>   +/**
>> + * page_pool_dev_cache_alloc() - allocate a cache.
>> + * @pool[in]:        pool from which to allocate
>> + * @size[in, out]:    in as the requested size, out as the allocated size
> 
> and here.


/**
 * page_pool_dev_cache_alloc() - allocate a cache.
 * @pool: pool from which to allocate
 * @size: in as the requested size, out as the allocated size
 *
 * Get a cache from the page allocator or page_pool caches.
 *
 * Return:
 * Returns the addr for the allocated cache, otherwise return NULL.
 */

> 
>> + *
>> + * Get a cache from the page allocator or page_pool caches.
>> + */
>>   static inline void *page_pool_dev_cache_alloc(struct page_pool *pool,
>>                             unsigned int *size)
>>   {
>> @@ -316,6 +354,14 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
>>       page_pool_put_full_page(pool, page, true);
>>   }
>>   +/**
>> + * page_pool_cache_free() - free a cache into the page_pool
>> + * @pool[in]:        pool from which cache was allocated
>> + * @data[in]:        cache to free
>> + * @allow_direct[in]:    freed by the consumer, allow lockless caching
> 
> and here.

/**
 * page_pool_cache_free() - free a cache into the page_pool
 * @pool: pool from which cache was allocated
 * @data: addr of cache to be free
 * @allow_direct: freed by the consumer, allow lockless caching
 *
 * Free a cache allocated from page_pool_dev_cache_alloc().
 */


> 
>> + *
>> + * Free a cache allocated from page_pool_dev_cache_alloc().
>> + */
>>   static inline void page_pool_cache_free(struct page_pool *pool, void *data,
>>                       bool allow_direct)
>>   {
> 
> Thanks.

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Yunsheng Lin]

On 2023/8/15 19:24, Simon Horman wrote:
> On Mon, Aug 14, 2023 at 08:56:38PM +0800, Yunsheng Lin wrote:
> 
> ...
> 
>> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
>> index 77cb75e63aca..d62c11aaea9a 100644
>> --- a/net/core/page_pool.c
>> +++ b/net/core/page_pool.c
> 
> ...
> 
>> @@ -737,18 +736,16 @@ static void page_pool_free_frag(struct page_pool *pool)
>>  	page_pool_return_page(pool, page);
>>  }
>>  
>> -struct page *page_pool_alloc_frag(struct page_pool *pool,
>> -				  unsigned int *offset,
>> -				  unsigned int size, gfp_t gfp)
>> +struct page *__page_pool_alloc_frag(struct page_pool *pool,
>> +				    unsigned int *offset,
>> +				    unsigned int size, gfp_t gfp)
>>  {
>>  	unsigned int max_size = PAGE_SIZE << pool->p.order;
>>  	struct page *page = pool->frag_page;
>>  
>> -	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
>> -		    size > max_size))
>> +	if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG))
> 
> Hi Yunsheng Lin,
> 
> There is a ')' missing on the line above, which results in a build failure.

Yes, thanks for noticing.
As the above checking is removed in patch 3, so it is not noticeable in testing
when the whole patchset is applied.

> 

Re: [PATCH net-next v6 5/6] page_pool: update document about frag API

[Randy Dunlap]

On 8/15/23 05:24, Yunsheng Lin wrote:
> On 2023/8/15 6:42, Randy Dunlap wrote:
>> Hi--
> Thanks for the reviewing.
> 
> ...
> 
>>> @@ -100,6 +115,14 @@ static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
>>>       return __page_pool_alloc_frag(pool, offset, size, gfp);
>>>   }
>>>   +/**
>>> + * page_pool_dev_alloc_frag() - allocate a page frag.
>>> + * @pool[in]    pool from which to allocate
>>> + * @offset[out]    offset to the allocated page
>>> + * @size[in]    requested size
>> Please use kernel-doc syntax/notation here.
> Will change to:

Thanks. Those look good.

-- 
~Randy

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Ilias Apalodimas]

Hi Yunsheng

On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> Currently page_pool_alloc_frag() is not supported in 32-bit
> arch with 64-bit DMA because of the overlap issue between
> pp_frag_count and dma_addr_upper in 'struct page' for those
> arches, which seems to be quite common, see [1], which means
> driver may need to handle it when using frag API.

That wasn't so common. IIRC it was a single TI platform that was breaking?

>
> In order to simplify the driver's work when using frag API
> this patch allows page_pool_alloc_frag() to call
> page_pool_alloc_pages() to return pages for those arches.

Do we have any use cases of people needing this?  Those architectures
should be long dead and although we have to support them in the
kernel,  I don't personally see the advantage of adjusting the API to
do that.  Right now we have a very clear separation between allocating
pages or fragments.   Why should we hide a page allocation under a
frag allocation?  A driver writer can simply allocate pages for those
boards.  Am I the only one not seeing a clean win here?

Thanks
/Ilias

>
> Add a PP_FLAG_PAGE_SPLIT_IN_DRIVER flag in order to fail the
> page_pool creation for 32-bit arch with 64-bit DMA when driver
> tries to do the page splitting itself.
>
> Note that it may aggravate truesize underestimate problem for
> skb as there is no page splitting for those pages, if driver
> need a accurate truesize, it may calculate that according to
> frag size, page order and PAGE_POOL_DMA_USE_PP_FRAG_COUNT
> being true or not. And we may provide a helper for that if it
> turns out to be helpful.
>
> 1. https://lore.kernel.org/all/20211117075652.58299-1-linyunsheng@huawei.com/
>
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> CC: Lorenzo Bianconi <lorenzo@kernel.org>
> CC: Alexander Duyck <alexander.duyck@gmail.com>
> CC: Liang Chen <liangchen.linux@gmail.com>
> CC: Alexander Lobakin <aleksander.lobakin@intel.com>
> ---
>  .../net/ethernet/mellanox/mlx5/core/en_main.c |  3 +-
>  include/net/page_pool/helpers.h               | 38 +++++++++++++++--
>  include/net/page_pool/types.h                 | 42 ++++++++++++-------
>  net/core/page_pool.c                          | 15 +++----
>  4 files changed, 68 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index bc9d5a5bea01..ec9c5a8cbda6 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -834,7 +834,8 @@ static int mlx5e_alloc_rq(struct mlx5e_params *params,
>                 struct page_pool_params pp_params = { 0 };
>
>                 pp_params.order     = 0;
> -               pp_params.flags     = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV | PP_FLAG_PAGE_FRAG;
> +               pp_params.flags     = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV |
> +                                       PP_FLAG_PAGE_SPLIT_IN_DRIVER;
>                 pp_params.pool_size = pool_size;
>                 pp_params.nid       = node;
>                 pp_params.dev       = rq->pdev;
> diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
> index 94231533a369..cb18de55f239 100644
> --- a/include/net/page_pool/helpers.h
> +++ b/include/net/page_pool/helpers.h
> @@ -29,8 +29,12 @@
>  #ifndef _NET_PAGE_POOL_HELPERS_H
>  #define _NET_PAGE_POOL_HELPERS_H
>
> +#include <linux/dma-mapping.h>
>  #include <net/page_pool/types.h>
>
> +#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT        \
> +               (sizeof(dma_addr_t) > sizeof(unsigned long))
> +
>  #ifdef CONFIG_PAGE_POOL_STATS
>  int page_pool_ethtool_stats_get_count(void);
>  u8 *page_pool_ethtool_stats_get_strings(u8 *data);
> @@ -73,6 +77,29 @@ static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
>         return page_pool_alloc_pages(pool, gfp);
>  }
>
> +static inline struct page *page_pool_alloc_frag(struct page_pool *pool,
> +                                               unsigned int *offset,
> +                                               unsigned int size, gfp_t gfp)
> +{
> +       unsigned int max_size = PAGE_SIZE << pool->p.order;
> +
> +       size = ALIGN(size, dma_get_cache_alignment());
> +
> +       if (WARN_ON(size > max_size))
> +               return NULL;
> +
> +       /* Don't allow page splitting and allocate one big frag
> +        * for 32-bit arch with 64-bit DMA, corresponding to
> +        * the checking in page_pool_is_last_frag().
> +        */
> +       if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT) {
> +               *offset = 0;
> +               return page_pool_alloc_pages(pool, gfp);
> +       }
> +
> +       return __page_pool_alloc_frag(pool, offset, size, gfp);
> +}
> +
>  static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
>                                                     unsigned int *offset,
>                                                     unsigned int size)
> @@ -134,8 +161,14 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
>  static inline bool page_pool_is_last_frag(struct page_pool *pool,
>                                           struct page *page)
>  {
> -       /* If fragments aren't enabled or count is 0 we were the last user */
> +       /* We assume we are the last frag user that is still holding
> +        * on to the page if:
> +        * 1. Fragments aren't enabled.
> +        * 2. We are running in 32-bit arch with 64-bit DMA.
> +        * 3. page_pool_defrag_page() indicate we are the last user.
> +        */
>         return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
> +              PAGE_POOL_DMA_USE_PP_FRAG_COUNT ||
>                (page_pool_defrag_page(page, 1) == 0);
>  }
>
> @@ -197,9 +230,6 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
>         page_pool_put_full_page(pool, page, true);
>  }
>
> -#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT        \
> -               (sizeof(dma_addr_t) > sizeof(unsigned long))
> -
>  /**
>   * page_pool_get_dma_addr() - Retrieve the stored DMA address.
>   * @page:      page allocated from a page pool
> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
> index 887e7946a597..079337c42aa6 100644
> --- a/include/net/page_pool/types.h
> +++ b/include/net/page_pool/types.h
> @@ -6,21 +6,29 @@
>  #include <linux/dma-direction.h>
>  #include <linux/ptr_ring.h>
>
> -#define PP_FLAG_DMA_MAP                BIT(0) /* Should page_pool do the DMA
> -                                       * map/unmap
> -                                       */
> -#define PP_FLAG_DMA_SYNC_DEV   BIT(1) /* If set all pages that the driver gets
> -                                       * from page_pool will be
> -                                       * DMA-synced-for-device according to
> -                                       * the length provided by the device
> -                                       * driver.
> -                                       * Please note DMA-sync-for-CPU is still
> -                                       * device driver responsibility
> -                                       */
> -#define PP_FLAG_PAGE_FRAG      BIT(2) /* for page frag feature */
> +/* Should page_pool do the DMA map/unmap */
> +#define PP_FLAG_DMA_MAP                        BIT(0)
> +
> +/* If set all pages that the driver gets from page_pool will be
> + * DMA-synced-for-device according to the length provided by the device driver.
> + * Please note DMA-sync-for-CPU is still device driver responsibility
> + */
> +#define PP_FLAG_DMA_SYNC_DEV           BIT(1)
> +
> +/* for page frag feature */
> +#define PP_FLAG_PAGE_FRAG              BIT(2)
> +
> +/* If set driver will do the page splitting itself. This is used to fail the
> + * page_pool creation because there is overlap issue between pp_frag_count and
> + * dma_addr_upper in 'struct page' for some arches with
> + * PAGE_POOL_DMA_USE_PP_FRAG_COUNT being true.
> + */
> +#define PP_FLAG_PAGE_SPLIT_IN_DRIVER   BIT(3)
> +
>  #define PP_FLAG_ALL            (PP_FLAG_DMA_MAP |\
>                                  PP_FLAG_DMA_SYNC_DEV |\
> -                                PP_FLAG_PAGE_FRAG)
> +                                PP_FLAG_PAGE_FRAG |\
> +                                PP_FLAG_PAGE_SPLIT_IN_DRIVER)
>
>  /*
>   * Fast allocation side cache array/stack
> @@ -45,7 +53,8 @@ struct pp_alloc_cache {
>
>  /**
>   * struct page_pool_params - page pool parameters
> - * @flags:     PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG
> + * @flags:     PP_FLAG_DMA_MAP, PP_FLAG_DMA_SYNC_DEV, PP_FLAG_PAGE_FRAG,
> + *             PP_FLAG_PAGE_SPLIT_IN_DRIVER
>   * @order:     2^order pages on allocation
>   * @pool_size: size of the ptr_ring
>   * @nid:       NUMA node id to allocate from pages from
> @@ -183,8 +192,9 @@ struct page_pool {
>  };
>
>  struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);
> -struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset,
> -                                 unsigned int size, gfp_t gfp);
> +struct page *__page_pool_alloc_frag(struct page_pool *pool,
> +                                   unsigned int *offset, unsigned int size,
> +                                   gfp_t gfp);
>  struct page_pool *page_pool_create(const struct page_pool_params *params);
>
>  struct xdp_mem_info;
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 77cb75e63aca..d62c11aaea9a 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -14,7 +14,6 @@
>  #include <net/xdp.h>
>
>  #include <linux/dma-direction.h>
> -#include <linux/dma-mapping.h>
>  #include <linux/page-flags.h>
>  #include <linux/mm.h> /* for put_page() */
>  #include <linux/poison.h>
> @@ -212,7 +211,7 @@ static int page_pool_init(struct page_pool *pool,
>         }
>
>         if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT &&
> -           pool->p.flags & PP_FLAG_PAGE_FRAG)
> +           pool->p.flags & PP_FLAG_PAGE_SPLIT_IN_DRIVER)
>                 return -EINVAL;
>
>  #ifdef CONFIG_PAGE_POOL_STATS
> @@ -737,18 +736,16 @@ static void page_pool_free_frag(struct page_pool *pool)
>         page_pool_return_page(pool, page);
>  }
>
> -struct page *page_pool_alloc_frag(struct page_pool *pool,
> -                                 unsigned int *offset,
> -                                 unsigned int size, gfp_t gfp)
> +struct page *__page_pool_alloc_frag(struct page_pool *pool,
> +                                   unsigned int *offset,
> +                                   unsigned int size, gfp_t gfp)
>  {
>         unsigned int max_size = PAGE_SIZE << pool->p.order;
>         struct page *page = pool->frag_page;
>
> -       if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
> -                   size > max_size))
> +       if (WARN_ON(!(pool->p.flags & PP_FLAG_PAGE_FRAG))
>                 return NULL;
>
> -       size = ALIGN(size, dma_get_cache_alignment());
>         *offset = pool->frag_offset;
>
>         if (page && *offset + size > max_size) {
> @@ -781,7 +778,7 @@ struct page *page_pool_alloc_frag(struct page_pool *pool,
>         alloc_stat_inc(pool, fast);
>         return page;
>  }
> -EXPORT_SYMBOL(page_pool_alloc_frag);
> +EXPORT_SYMBOL(__page_pool_alloc_frag);
>
>  static void page_pool_empty_ring(struct page_pool *pool)
>  {
> --
> 2.33.0
>

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Yunsheng Lin]

On 2023/8/16 19:26, Ilias Apalodimas wrote:
> Hi Yunsheng
> 
> On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>>
>> Currently page_pool_alloc_frag() is not supported in 32-bit
>> arch with 64-bit DMA because of the overlap issue between
>> pp_frag_count and dma_addr_upper in 'struct page' for those
>> arches, which seems to be quite common, see [1], which means
>> driver may need to handle it when using frag API.
> 
> That wasn't so common. IIRC it was a single TI platform that was breaking?

I am not so sure about that as grepping 'ARM_LPAE' has a long
list for that.

> 
>>
>> In order to simplify the driver's work when using frag API
>> this patch allows page_pool_alloc_frag() to call
>> page_pool_alloc_pages() to return pages for those arches.
> 
> Do we have any use cases of people needing this?  Those architectures
> should be long dead and although we have to support them in the
> kernel,  I don't personally see the advantage of adjusting the API to
> do that.  Right now we have a very clear separation between allocating
> pages or fragments.   Why should we hide a page allocation under a
> frag allocation?  A driver writer can simply allocate pages for those
> boards.  Am I the only one not seeing a clean win here?

It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag
in this patchset.

> 
> Thanks
> /Ilias
> 

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Ilias Apalodimas]

On Wed, 16 Aug 2023 at 15:49, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/8/16 19:26, Ilias Apalodimas wrote:
> > Hi Yunsheng
> >
> > On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@huawei.com> wrote:
> >>
> >> Currently page_pool_alloc_frag() is not supported in 32-bit
> >> arch with 64-bit DMA because of the overlap issue between
> >> pp_frag_count and dma_addr_upper in 'struct page' for those
> >> arches, which seems to be quite common, see [1], which means
> >> driver may need to handle it when using frag API.
> >
> > That wasn't so common. IIRC it was a single TI platform that was breaking?
>
> I am not so sure about that as grepping 'ARM_LPAE' has a long
> list for that.

Shouldn't we be grepping for CONFIG_ARCH_DMA_ADDR_T_64BIT and
PHYS_ADDR_T_64BIT to find the affected platforms?  Why LPAE?

>
> >
> >>
> >> In order to simplify the driver's work when using frag API
> >> this patch allows page_pool_alloc_frag() to call
> >> page_pool_alloc_pages() to return pages for those arches.
> >
> > Do we have any use cases of people needing this?  Those architectures
> > should be long dead and although we have to support them in the
> > kernel,  I don't personally see the advantage of adjusting the API to
> > do that.  Right now we have a very clear separation between allocating
> > pages or fragments.   Why should we hide a page allocation under a
> > frag allocation?  A driver writer can simply allocate pages for those
> > boards.  Am I the only one not seeing a clean win here?
>
> It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag
> in this patchset.

Yes, that happens *because* of this patchset.  I am not against the
change.  In fact, I'll have a closer look tomorrow.  I am just trying
to figure out if we really need it.  When the recycling patches were
introduced into page pool we had a very specific reason.  Due to the
XDP verifier we *had* to allocate a packet per page.  That was
expensive so we added the recycling capabilities to compensate and get
some performance back. Eventually we added page fragments and had a
very clear separation on the API.

Regards
/Ilias
>
> >
> > Thanks
> > /Ilias
> >

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Yunsheng Lin]

On 2023/8/17 1:01, Ilias Apalodimas wrote:
> On Wed, 16 Aug 2023 at 15:49, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>>
>> On 2023/8/16 19:26, Ilias Apalodimas wrote:
>>> Hi Yunsheng
>>>
>>> On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>>>>
>>>> Currently page_pool_alloc_frag() is not supported in 32-bit
>>>> arch with 64-bit DMA because of the overlap issue between
>>>> pp_frag_count and dma_addr_upper in 'struct page' for those
>>>> arches, which seems to be quite common, see [1], which means
>>>> driver may need to handle it when using frag API.
>>>
>>> That wasn't so common. IIRC it was a single TI platform that was breaking?
>>
>> I am not so sure about that as grepping 'ARM_LPAE' has a long
>> list for that.
> 
> Shouldn't we be grepping for CONFIG_ARCH_DMA_ADDR_T_64BIT and
> PHYS_ADDR_T_64BIT to find the affected platforms?  Why LPAE?


I used the key in the  original report:

https://www.spinics.net/lists/netdev/msg779890.html

>> Please see the bisection report below about a boot failure on
>> rk3288-rock2-square which is pointing to this patch.  The issue
>> appears to only happen with CONFIG_ARM_LPAE=y.

grepping the 'CONFIG_PHYS_ADDR_T_64BIT' seems to be more common?
https://elixir.free-electrons.com/linux/v6.4-rc6/K/ident/CONFIG_PHYS_ADDR_T_64BIT

> 
>>
>>>
>>>>
>>>> In order to simplify the driver's work when using frag API
>>>> this patch allows page_pool_alloc_frag() to call
>>>> page_pool_alloc_pages() to return pages for those arches.
>>>
>>> Do we have any use cases of people needing this?  Those architectures
>>> should be long dead and although we have to support them in the
>>> kernel,  I don't personally see the advantage of adjusting the API to
>>> do that.  Right now we have a very clear separation between allocating
>>> pages or fragments.   Why should we hide a page allocation under a
>>> frag allocation?  A driver writer can simply allocate pages for those
>>> boards.  Am I the only one not seeing a clean win here?
>>
>> It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag
>> in this patchset.
> 
> Yes, that happens *because* of this patchset.  I am not against the
> change.  In fact, I'll have a closer look tomorrow.  I am just trying
> to figure out if we really need it.  When the recycling patches were
> introduced into page pool we had a very specific reason.  Due to the
> XDP verifier we *had* to allocate a packet per page.  That was

Did you mean a xdp frame containing a frag page can not be passed to the
xdp core?
What is exact reason why the XDP verifier need a packet per page?
Is there a code block that you can point me to?

I wonder if it is still the case for now, as bnxt and mlx5 seems to be
supporting frag page and xdp now.

> expensive so we added the recycling capabilities to compensate and get
> some performance back. Eventually we added page fragments and had a
> very clear separation on the API.
> 
> Regards
> /Ilias
>>
>>>
>>> Thanks
>>> /Ilias
>>>
> .
> 

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Ilias Apalodimas]

On Thu, 17 Aug 2023 at 12:06, Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/8/17 1:01, Ilias Apalodimas wrote:
> > On Wed, 16 Aug 2023 at 15:49, Yunsheng Lin <linyunsheng@huawei.com> wrote:
> >>
> >> On 2023/8/16 19:26, Ilias Apalodimas wrote:
> >>> Hi Yunsheng
> >>>
> >>> On Mon, 14 Aug 2023 at 15:59, Yunsheng Lin <linyunsheng@huawei.com> wrote:
> >>>>
> >>>> Currently page_pool_alloc_frag() is not supported in 32-bit
> >>>> arch with 64-bit DMA because of the overlap issue between
> >>>> pp_frag_count and dma_addr_upper in 'struct page' for those
> >>>> arches, which seems to be quite common, see [1], which means
> >>>> driver may need to handle it when using frag API.
> >>>
> >>> That wasn't so common. IIRC it was a single TI platform that was breaking?
> >>
> >> I am not so sure about that as grepping 'ARM_LPAE' has a long
> >> list for that.
> >
> > Shouldn't we be grepping for CONFIG_ARCH_DMA_ADDR_T_64BIT and
> > PHYS_ADDR_T_64BIT to find the affected platforms?  Why LPAE?
>
>
> I used the key in the  original report:
>
> https://www.spinics.net/lists/netdev/msg779890.html
>
> >> Please see the bisection report below about a boot failure on
> >> rk3288-rock2-square which is pointing to this patch.  The issue
> >> appears to only happen with CONFIG_ARM_LPAE=y.
>
> grepping the 'CONFIG_PHYS_ADDR_T_64BIT' seems to be more common?
> https://elixir.free-electrons.com/linux/v6.4-rc6/K/ident/CONFIG_PHYS_ADDR_T_64BIT
>

Yes, grepping around a bit uncovered this arch/arm/mm/Kconfig, which
enables PHYS_ADDR_T_64BIT if ARM_LPAE is enabled.  Then
ARCH_DMA_ADDR_T_64BIT
is also enabled from kernel/dma/Kconfig.  But that doesn't mean
grepping for any of those uncovers all the problematic platforms,
there are more than Arm platforms.  The ones that will actually fail
are
- ARCH_DMA_ADDR_T_64BIT is enabled and it's a 32bit architecture
- You have a network driver for that platform that uses page pool.

The combination of these shouldn't be that common.  The only one that
comes to mind is the stmmac driver, which the report was for.

> >
> >>
> >>>
> >>>>
> >>>> In order to simplify the driver's work when using frag API
> >>>> this patch allows page_pool_alloc_frag() to call
> >>>> page_pool_alloc_pages() to return pages for those arches.
> >>>
> >>> Do we have any use cases of people needing this?  Those architectures
> >>> should be long dead and although we have to support them in the
> >>> kernel,  I don't personally see the advantage of adjusting the API to
> >>> do that.  Right now we have a very clear separation between allocating
> >>> pages or fragments.   Why should we hide a page allocation under a
> >>> frag allocation?  A driver writer can simply allocate pages for those
> >>> boards.  Am I the only one not seeing a clean win here?
> >>
> >> It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag
> >> in this patchset.
> >
> > Yes, that happens *because* of this patchset.  I am not against the
> > change.  In fact, I'll have a closer look tomorrow.  I am just trying
> > to figure out if we really need it.  When the recycling patches were
> > introduced into page pool we had a very specific reason.  Due to the
> > XDP verifier we *had* to allocate a packet per page.  That was
>
> Did you mean a xdp frame containing a frag page can not be passed to the
> xdp core?
> What is exact reason why the XDP verifier need a packet per page?
> Is there a code block that you can point me to?

It's been a while since I looked at this, but doesn't __xdp_return()
still sync the entire page if the mem type comes from page_pool?

>
> I wonder if it is still the case for now, as bnxt and mlx5 seems to be
> supporting frag page and xdp now.

I only looked at bnxt, but that doesnt seem to be entirely true.  That
code still allocates pages if an XDP prog is installed.  The only case
where it allocates fragments is if the kernel is compiled with 65k
pages, but the hardware doesnt support that (check for
BNXT_RX_PAGE_SHIFT)


Thanks
/Ilias
>
> > expensive so we added the recycling capabilities to compensate and get
> > some performance back. Eventually we added page fragments and had a
> > very clear separation on the API.
> >
> > Regards
> > /Ilias
> >>
> >>>
> >>> Thanks
> >>> /Ilias
> >>>
> > .
> >

Re: [PATCH net-next v6 1/6] page_pool: frag API support for 32-bit arch with 64-bit DMA

[Yunsheng Lin]

On 2023/8/17 19:43, Ilias Apalodimas wrote:
>>>>>>
>>>>>> In order to simplify the driver's work when using frag API
>>>>>> this patch allows page_pool_alloc_frag() to call
>>>>>> page_pool_alloc_pages() to return pages for those arches.
>>>>>
>>>>> Do we have any use cases of people needing this?  Those architectures
>>>>> should be long dead and although we have to support them in the
>>>>> kernel,  I don't personally see the advantage of adjusting the API to
>>>>> do that.  Right now we have a very clear separation between allocating
>>>>> pages or fragments.   Why should we hide a page allocation under a
>>>>> frag allocation?  A driver writer can simply allocate pages for those
>>>>> boards.  Am I the only one not seeing a clean win here?
>>>>
>>>> It is also a part of removing the per page_pool PP_FLAG_PAGE_FRAG flag
>>>> in this patchset.
>>>
>>> Yes, that happens *because* of this patchset.  I am not against the
>>> change.  In fact, I'll have a closer look tomorrow.  I am just trying
>>> to figure out if we really need it.  When the recycling patches were
>>> introduced into page pool we had a very specific reason.  Due to the
>>> XDP verifier we *had* to allocate a packet per page.  That was
>>
>> Did you mean a xdp frame containing a frag page can not be passed to the
>> xdp core?
>> What is exact reason why the XDP verifier need a packet per page?
>> Is there a code block that you can point me to?
> 
> It's been a while since I looked at this, but doesn't __xdp_return()
> still sync the entire page if the mem type comes from page_pool?

Yes, I checked that too.
It is supposed to sync the entire page if the mem type comes from page_pool,
as it depend on the last freed frag to do the sync_for_device operation.