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

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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: Byungchul Park <byungchul@sk.com>
Link: https://patch.msgid.link/20250721021835.63939-4-byungchul@sk.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Byungchul Park 2025-07-21 11:18:26 +09:00 committed by Jakub Kicinski
parent 38a436d4e2
commit 89ade7c730
3 changed files with 22 additions and 3 deletions
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4
drivers/net/ethernet/mellanox/mlx4/en_rx.c
View File

@ -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) {

4
include/linux/mm.h
View File

@ -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;
}

17
include/net/netmem.h
View File

@ -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