__xdp_build_skb_from_frame() was the last user of
{__,}xdp_release_frame(), which detaches pages from the page_pool.
All the consumers now recycle Page Pool skbs and page, except mlx5,
stmmac and tsnep drivers, which use page_pool_release_page() directly
(might change one day). It's safe to assume this functionality is not
needed anymore and can be removed (in favor of recycling).

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
 include/net/xdp.h | 29 -----------------------------
 net/core/xdp.c    | 15 ---------------
 2 files changed, 44 deletions(-)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index d517bfac937b..5393b3ebe56e 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -317,35 +317,6 @@ void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq);
 void xdp_return_frame_bulk(struct xdp_frame *xdpf,
 			   struct xdp_frame_bulk *bq);
 
-/* When sending xdp_frame into the network stack, then there is no
- * return point callback, which is needed to release e.g. DMA-mapping
- * resources with page_pool.  Thus, have explicit function to release
- * frame resources.
- */
-void __xdp_release_frame(void *data, struct xdp_mem_info *mem);
-static inline void xdp_release_frame(struct xdp_frame *xdpf)
-{
-	struct xdp_mem_info *mem = &xdpf->mem;
-	struct skb_shared_info *sinfo;
-	int i;
-
-	/* Curr only page_pool needs this */
-	if (mem->type != MEM_TYPE_PAGE_POOL)
-		return;
-
-	if (likely(!xdp_frame_has_frags(xdpf)))
-		goto out;
-
-	sinfo = xdp_get_shared_info_from_frame(xdpf);
-	for (i = 0; i < sinfo->nr_frags; i++) {
-		struct page *page = skb_frag_page(&sinfo->frags[i]);
-
-		__xdp_release_frame(page_address(page), mem);
-	}
-out:
-	__xdp_release_frame(xdpf->data, mem);
-}
-
 static __always_inline unsigned int xdp_get_frame_len(struct xdp_frame *xdpf)
 {
 	struct skb_shared_info *sinfo;
diff --git a/net/core/xdp.c b/net/core/xdp.c
index a2237cfca8e9..8d3ad315f18d 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -531,21 +531,6 @@ void xdp_return_buff(struct xdp_buff *xdp)
 }
 EXPORT_SYMBOL_GPL(xdp_return_buff);
 
-/* Only called for MEM_TYPE_PAGE_POOL see xdp.h */
-void __xdp_release_frame(void *data, struct xdp_mem_info *mem)
-{
-	struct xdp_mem_allocator *xa;
-	struct page *page;
-
-	rcu_read_lock();
-	xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
-	page = virt_to_head_page(data);
-	if (xa)
-		page_pool_release_page(xa->page_pool, page);
-	rcu_read_unlock();
-}
-EXPORT_SYMBOL_GPL(__xdp_release_frame);
-
 void xdp_attachment_setup(struct xdp_attachment_info *info,
 			  struct netdev_bpf *bpf)
 {
-- 
2.39.2

On 2023/3/14 5:55, Alexander Lobakin wrote:
> __xdp_build_skb_from_frame() was the last user of
> {__,}xdp_release_frame(), which detaches pages from the page_pool.
> All the consumers now recycle Page Pool skbs and page, except mlx5,
> stmmac and tsnep drivers, which use page_pool_release_page() directly
> (might change one day). It's safe to assume this functionality is not
> needed anymore and can be removed (in favor of recycling).
> 
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> ---
>  include/net/xdp.h | 29 -----------------------------
>  net/core/xdp.c    | 15 ---------------
>  2 files changed, 44 deletions(-)
> 
> diff --git a/include/net/xdp.h b/include/net/xdp.h
> index d517bfac937b..5393b3ebe56e 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -317,35 +317,6 @@ void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq);
>  void xdp_return_frame_bulk(struct xdp_frame *xdpf,
>  			   struct xdp_frame_bulk *bq);
>  
> -/* When sending xdp_frame into the network stack, then there is no
> - * return point callback, which is needed to release e.g. DMA-mapping
> - * resources with page_pool.  Thus, have explicit function to release
> - * frame resources.
> - */
> -void __xdp_release_frame(void *data, struct xdp_mem_info *mem);
> -static inline void xdp_release_frame(struct xdp_frame *xdpf)
> -{
> -	struct xdp_mem_info *mem = &xdpf->mem;
> -	struct skb_shared_info *sinfo;
> -	int i;
> -
> -	/* Curr only page_pool needs this */
> -	if (mem->type != MEM_TYPE_PAGE_POOL)
> -		return;
> -
> -	if (likely(!xdp_frame_has_frags(xdpf)))
> -		goto out;
> -
> -	sinfo = xdp_get_shared_info_from_frame(xdpf);
> -	for (i = 0; i < sinfo->nr_frags; i++) {
> -		struct page *page = skb_frag_page(&sinfo->frags[i]);
> -
> -		__xdp_release_frame(page_address(page), mem);
> -	}
> -out:
> -	__xdp_release_frame(xdpf->data, mem);
> -}
> -
>  static __always_inline unsigned int xdp_get_frame_len(struct xdp_frame *xdpf)
>  {
>  	struct skb_shared_info *sinfo;
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index a2237cfca8e9..8d3ad315f18d 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -531,21 +531,6 @@ void xdp_return_buff(struct xdp_buff *xdp)
>  }
>  EXPORT_SYMBOL_GPL(xdp_return_buff);
>  
> -/* Only called for MEM_TYPE_PAGE_POOL see xdp.h */
> -void __xdp_release_frame(void *data, struct xdp_mem_info *mem)
> -{
> -	struct xdp_mem_allocator *xa;
> -	struct page *page;
> -
> -	rcu_read_lock();
> -	xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
> -	page = virt_to_head_page(data);
> -	if (xa)
> -		page_pool_release_page(xa->page_pool, page);

page_pool_release_page() is only call here when xa is not NULL
and mem->type == MEM_TYPE_PAGE_POOL.

But skb_mark_for_recycle() is call when mem->type == MEM_TYPE_PAGE_POOL
without checking xa, it does not seems symmetric to patch 3, if this is
intended?

> -	rcu_read_unlock();
> -}
> -EXPORT_SYMBOL_GPL(__xdp_release_frame);
> -
>  void xdp_attachment_setup(struct xdp_attachment_info *info,
>  			  struct netdev_bpf *bpf)
>  {
>

From: Yunsheng Lin <linyunsheng@huawei.com>
Date: Tue, 14 Mar 2023 19:37:23 +0800

> On 2023/3/14 5:55, Alexander Lobakin wrote:
>> __xdp_build_skb_from_frame() was the last user of
>> {__,}xdp_release_frame(), which detaches pages from the page_pool.

[...]

>> -/* Only called for MEM_TYPE_PAGE_POOL see xdp.h */
>> -void __xdp_release_frame(void *data, struct xdp_mem_info *mem)
>> -{
>> -	struct xdp_mem_allocator *xa;
>> -	struct page *page;
>> -
>> -	rcu_read_lock();
>> -	xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
>> -	page = virt_to_head_page(data);
>> -	if (xa)
>> -		page_pool_release_page(xa->page_pool, page);
> 
> page_pool_release_page() is only call here when xa is not NULL
> and mem->type == MEM_TYPE_PAGE_POOL.
> 
> But skb_mark_for_recycle() is call when mem->type == MEM_TYPE_PAGE_POOL
> without checking xa, it does not seems symmetric to patch 3, if this is
> intended?

Intended. page_pool_return_skb_page() checks for %PP_SIGNATURE and if
a page doesn't belong to any PP, it will be returned to the MM layer.
Moreover, cases `mem->type == MEM_TYPE_PAGE_POOL && xa == NULL` are more
of an exception rather than regular -- this means the page was released
from its PP before reaching the function and IIRC it's even impossible
with our current drivers. Adding a hashtable lookup to
{__,}xdp_build_skb_from_frame() would only add hotpath overhead with no
positive impact.

> 
>> -	rcu_read_unlock();
>> -}
>> -EXPORT_SYMBOL_GPL(__xdp_release_frame);
>> -
>>  void xdp_attachment_setup(struct xdp_attachment_info *info,
>>  			  struct netdev_bpf *bpf)
>>  {
>>

Thanks,
Olek