[PATCH net-next v5 1/2] page_pool: Move pp_magic check into helper functions

Toke Høiland-Jørgensen
2025-03-28T12:19:24Z

Since we are about to stash some more information into the pp_magic
field, let's move the magic signature checks into a pair of helper
functions so it can be changed in one place.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Tested-by: Yonglong Liu <liuyonglong@huawei.com>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 4 ++--
include/net/page_pool/types.h | 18 ++++++++++++++++++
mm/page_alloc.c | 9 +++------
net/core/netmem_priv.h | 5 +++++
net/core/skbuff.c | 16 ++--------------
net/core/xdp.c | 4 ++--
6 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index f803e1c93590068d3a7829b0683be4af019266d1..5ce1b463b7a8dd7969e391618658d66f6e836cc1 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -707,8 +707,8 @@ static void mlx5e_free_xdpsq_desc(struct mlx5e_xdpsq *sq,
xdpi = mlx5e_xdpi_fifo_pop(xdpi_fifo);
page = xdpi.page.page;

- /* No need to check ((page->pp_magic & ~0x3UL) == PP_SIGNATURE)
- * as we know this is a page_pool page.
+ /* No need to check page_pool_page_is_pp() as we
+ * know this is a page_pool page.
*/
page_pool_recycle_direct(page->pp, page);
} while (++n < num);
diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 36eb57d73abc6cfc601e700ca08be20fb8281055..df0d3c1608929605224feb26173135ff37951ef8 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -54,6 +54,14 @@ struct pp_alloc_cache {
netmem_ref cache[PP_ALLOC_CACHE_SIZE];
};

+/* Mask used for checking in page_pool_page_is_pp() below. page->pp_magic is
+ * OR'ed with PP_SIGNATURE after the allocation in order to preserve bit 0 for
+ * the head page of compound page and bit 1 for pfmemalloc page.
+ * page_is_pfmemalloc() is checked in __page_pool_put_page() to avoid recycling
+ * the pfmemalloc page.
+ */
+#define PP_MAGIC_MASK ~0x3UL
+
/**
* struct page_pool_params - page pool parameters
* @fast: params accessed frequently on hotpath
@@ -264,6 +272,11 @@ void page_pool_destroy(struct page_pool *pool);
void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
const struct xdp_mem_info *mem);
void page_pool_put_netmem_bulk(netmem_ref *data, u32 count);
+
+static inline bool page_pool_page_is_pp(struct page *page)
+{
+ return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE;
+}
#else
static inline void page_pool_destroy(struct page_pool *pool)
{
@@ -278,6 +291,11 @@ static inline void page_pool_use_xdp_mem(struct page_pool *pool,
static inline void page_pool_put_netmem_bulk(netmem_ref *data, u32 count)
{
}
+
+static inline bool page_pool_page_is_pp(struct page *page)
+{
+ return false;
+}
#endif

void page_pool_put_unrefed_netmem(struct page_pool *pool, netmem_ref netmem,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 542d25f77be80304b731411ffd29b276ee13be0c..3535ee76afe946cbb042ecbce603bdbedc9233b9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -55,6 +55,7 @@
#include <linux/delayacct.h>
#include <linux/cacheinfo.h>
#include <linux/pgalloc_tag.h>
+#include <net/page_pool/types.h>
#include <asm/div64.h>
#include "internal.h"
#include "shuffle.h"
@@ -872,9 +873,7 @@ static inline bool page_expected_state(struct page *page,
#ifdef CONFIG_MEMCG
page->memcg_data |
#endif
-#ifdef CONFIG_PAGE_POOL
- ((page->pp_magic & ~0x3UL) == PP_SIGNATURE) |
-#endif
+ page_pool_page_is_pp(page) |
(page->flags & check_flags)))
return false;

@@ -901,10 +900,8 @@ static const char *page_bad_reason(struct page *page, unsigned long flags)
if (unlikely(page->memcg_data))
bad_reason = "page still charged to cgroup";
#endif
-#ifdef CONFIG_PAGE_POOL
- if (unlikely((page->pp_magic & ~0x3UL) == PP_SIGNATURE))
+ if (unlikely(page_pool_page_is_pp(page)))
bad_reason = "page_pool leak";
-#endif
return bad_reason;
}

diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h
index 7eadb8393e002fd1cc2cef8a313d2ea7df76f301..f33162fd281c23e109273ba09950c5d0a2829bc9 100644
--- a/net/core/netmem_priv.h
+++ b/net/core/netmem_priv.h
@@ -18,6 +18,11 @@ static inline void netmem_clear_pp_magic(netmem_ref netmem)
__netmem_clear_lsb(netmem)->pp_magic = 0;
}

+static inline bool netmem_is_pp(netmem_ref netmem)
+{
+ return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_SIGNATURE;
+}
+
static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool)
{
__netmem_clear_lsb(netmem)->pp = pool;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 6cbf77bc61fce74c934628fd74b3a2cb7809e464..74a2d886a35b518d55b6d3cafcb8442212f9beee 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -893,11 +893,6 @@ static void skb_clone_fraglist(struct sk_buff *skb)
skb_get(list);
}

-static bool is_pp_netmem(netmem_ref netmem)
-{
- return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
-}
-
int skb_pp_cow_data(struct page_pool *pool, struct sk_buff **pskb,
unsigned int headroom)
{
@@ -995,14 +990,7 @@ bool napi_pp_put_page(netmem_ref netmem)
{
netmem = netmem_compound_head(netmem);

- /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
- * in order to preserve any existing bits, such as bit 0 for the
- * head page of compound page and bit 1 for pfmemalloc page, so
- * mask those bits for freeing side when doing below checking,
- * and page_is_pfmemalloc() is checked in __page_pool_put_page()
- * to avoid recycling the pfmemalloc page.
- */
- if (unlikely(!is_pp_netmem(netmem)))
+ if (unlikely(!netmem_is_pp(netmem)))
return false;

page_pool_put_full_netmem(netmem_get_pp(netmem), netmem, false);
@@ -1042,7 +1030,7 @@ static int skb_pp_frag_ref(struct sk_buff *skb)

for (i = 0; i < shinfo->nr_frags; i++) {
head_netmem = netmem_compound_head(shinfo->frags[i].netmem);
- if (likely(is_pp_netmem(head_netmem)))
+ if (likely(netmem_is_pp(head_netmem)))
page_pool_ref_netmem(head_netmem);
else
page_ref_inc(netmem_to_page(head_netmem));
diff --git a/net/core/xdp.c b/net/core/xdp.c
index f86eedad586a77eb63a96a85aa6d068d3e94f077..0ba73943c6eed873b3d1c681b3b9a802b590f2d9 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -437,8 +437,8 @@ void __xdp_return(netmem_ref netmem, enum xdp_mem_type mem_type,
netmem = netmem_compound_head(netmem);
if (napi_direct && xdp_return_frame_no_direct())
napi_direct = false;
- /* No need to check ((page->pp_magic & ~0x3UL) == PP_SIGNATURE)
- * as mem->type knows this a page_pool page
+ /* No need to check netmem_is_pp() as mem->type knows this a
+ * page_pool page
*/
page_pool_put_full_netmem(netmem_get_pp(netmem), netmem,
napi_direct);

--
2.48.1