Commit 89ade7c7 authored by Byungchul Park's avatar Byungchul Park Committed by Jakub Kicinski
Browse files

netmem, mlx4: access ->pp_ref_count through netmem_desc instead of page 



To eliminate the use of struct page in page pool, the page pool users
should use netmem descriptor and APIs instead.

Make mlx4 access ->pp_ref_count through netmem_desc instead of page.

While at it, add a helper, pp_page_to_nmdesc() and __pp_page_to_nmdesc(),
that can be used to get netmem_desc from page only if it's a pp page.
For now that netmem_desc overlays on page, it can be achieved by just
casting, and use macro and _Generic to cover const casting as well.

Plus, change page_pool_page_is_pp() to check for 'const struct page *'
instead of 'struct page *' since it doesn't modify data and additionally
covers const type.

Signed-off-by: default avatarByungchul Park <byungchul@sk.com>
Link: https://patch.msgid.link/20250721021835.63939-4-byungchul@sk.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 38a436d4

drivers/net/ethernet/mellanox/mlx4/en_rx.c

+3 −1
Original line number Diff line number Diff line
@@ -460,9 +460,11 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv, 


		truesize += frag_info->frag_stride;

		if (frag_info->frag_stride == PAGE_SIZE / 2) {

			struct netmem_desc *desc = pp_page_to_nmdesc(page);



			frags->page_offset ^= PAGE_SIZE / 2;

			release = page_count(page) != 1 ||

				  atomic_long_read(&page->pp_ref_count) != 1 ||

				  atomic_long_read(&desc->pp_ref_count) != 1 ||

				  page_is_pfmemalloc(page) ||

				  page_to_nid(page) != numa_mem_id();

		} else if (!priv->rx_headroom) {

include/linux/mm.h

+2 −2
Original line number Diff line number Diff line
@@ -4178,12 +4178,12 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status); 
#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)



#ifdef CONFIG_PAGE_POOL

static inline bool page_pool_page_is_pp(struct page *page)

static inline bool page_pool_page_is_pp(const struct page *page)

{

	return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;

}

#else

static inline bool page_pool_page_is_pp(struct page *page)

static inline bool page_pool_page_is_pp(const struct page *page)

{

	return false;

}

include/net/netmem.h

+17 −0
Original line number Diff line number Diff line
@@ -285,6 +285,23 @@ static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem) 
	return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);

}



/* XXX: How to extract netmem_desc from page must be changed, once

 * netmem_desc no longer overlays on page and will be allocated through

 * slab.

 */

#define __pp_page_to_nmdesc(p)	(_Generic((p),				\

	const struct page * :	(const struct netmem_desc *)(p),	\

	struct page * :		(struct netmem_desc *)(p)))



/* CAUTION: Check if the page is a pp page before calling this helper or

 * know it's a pp page.

 */

#define pp_page_to_nmdesc(p)						\

({									\

	DEBUG_NET_WARN_ON_ONCE(!page_pool_page_is_pp(p));		\

	__pp_page_to_nmdesc(p);						\

})



/**

 * __netmem_get_pp - unsafely get pointer to the &page_pool backing @netmem

 * @netmem: netmem reference to get the pointer from