On 21.07.25 07:49, Byungchul Park wrote:
Hi,
I focused on converting the existing APIs accessing ->pp_magic field to
page type APIs. However, yes. Additional works would better be
considered on top like:
1. Adjust how to store and retrieve dma index. Maybe network guys
can work better on top.
2. Move the sanity check for page pool in mm/page_alloc.c to on free.
Byungchul
---8<---
From 7d207a1b3e9f4ff2a72f5b54b09e3ed0c4aaaca3 Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul@xxxxxx>
Date: Mon, 21 Jul 2025 14:05:20 +0900
Subject: [PATCH] mm, page_pool: introduce a new page type for page pool in page type
->pp_magic field in struct page is current used to identify if a page
belongs to a page pool. However, page type e.i. PGTY_netpp can be used
for that purpose.
Use the page type APIs e.g. PageNetpp(), __SetPageNetpp(), and
__ClearPageNetpp() instead, and remove the existing APIs accessing
->pp_magic e.g. page_pool_page_is_pp(), netmem_or_pp_magic(), and
netmem_clear_pp_magic() since they are totally replaced.
This work was inspired by the following link by Pavel:
[1] https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@xxxxxxxxx/
I'm, sure you saw my comment (including my earlier suggestion for using
a page type), in particular around ...
---
.../net/ethernet/mellanox/mlx5/core/en/xdp.c | 2 +-
include/linux/mm.h | 28 ++-----------------
include/linux/page-flags.h | 6 ++++
include/net/netmem.h | 2 +-
mm/page_alloc.c | 4 +--
net/core/netmem_priv.h | 16 ++---------
net/core/page_pool.c | 10 +++++--
7 files changed, 24 insertions(+), 44 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 5d51600935a6..def274f5c1ca 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -707,7 +707,7 @@ 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_pool_page_is_pp() as we
+ /* No need to check PageNetpp() as we
* know this is a page_pool page.
*/
page_pool_recycle_direct(pp_page_to_nmdesc(page)->pp,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ae50c1641bed..736061749535 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4135,10 +4135,9 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
* DMA mapping IDs for page_pool
*
* When DMA-mapping a page, page_pool allocates an ID (from an xarray) and
- * stashes it in the upper bits of page->pp_magic. We always want to be able to
- * unambiguously identify page pool pages (using page_pool_page_is_pp()). Non-PP
- * pages can have arbitrary kernel pointers stored in the same field as pp_magic
- * (since it overlaps with page->lru.next), so we must ensure that we cannot
+ * stashes it in the upper bits of page->pp_magic. Non-PP pages can have
+ * arbitrary kernel pointers stored in the same field as pp_magic (since
+ * it overlaps with page->lru.next), so we must ensure that we cannot
* mistake a valid kernel pointer with any of the values we write into this
* field.
*
@@ -4168,25 +4167,4 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status);
#define PP_DMA_INDEX_MASK GENMASK(PP_DMA_INDEX_BITS + PP_DMA_INDEX_SHIFT - 1, \
PP_DMA_INDEX_SHIFT)
-
-/* 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, as well as the
- * bits used for the DMA index. page_is_pfmemalloc() is checked in
- * __page_pool_put_page() to avoid recycling the pfmemalloc page.
- */
-#define PP_MAGIC_MASK ~(PP_DMA_INDEX_MASK | 0x3UL)
-
-#ifdef CONFIG_PAGE_POOL
-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(const struct page *page)
-{
- return false;
-}
-#endif
-
#endif /* _LINUX_MM_H */
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 4fe5ee67535b..906ba7c9e372 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -957,6 +957,7 @@ enum pagetype {
PGTY_zsmalloc = 0xf6,
PGTY_unaccepted = 0xf7,
PGTY_large_kmalloc = 0xf8,
+ PGTY_netpp = 0xf9,
PGTY_mapcount_underflow = 0xff
};
@@ -1101,6 +1102,11 @@ PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc)
PAGE_TYPE_OPS(Unaccepted, unaccepted, unaccepted)
FOLIO_TYPE_OPS(large_kmalloc, large_kmalloc)
+/*
+ * Marks page_pool allocated pages.
+ */
+PAGE_TYPE_OPS(Netpp, netpp, netpp)
+
/**
* PageHuge - Determine if the page belongs to hugetlbfs
* @page: The page to test.
diff --git a/include/net/netmem.h b/include/net/netmem.h
index f7dacc9e75fd..3667334e16e7 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -298,7 +298,7 @@ static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
*/
#define pp_page_to_nmdesc(p) \
({ \
- DEBUG_NET_WARN_ON_ONCE(!page_pool_page_is_pp(p)); \
+ DEBUG_NET_WARN_ON_ONCE(!PageNetpp(p)); \
__pp_page_to_nmdesc(p); \
})
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ef3c07266b3..71c7666e48a9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -898,7 +898,7 @@ static inline bool page_expected_state(struct page *page,
#ifdef CONFIG_MEMCG
page->memcg_data |
#endif
- page_pool_page_is_pp(page) |
+ PageNetpp(page) |
(page->flags & check_flags)))
return false;
@@ -925,7 +925,7 @@ 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
- if (unlikely(page_pool_page_is_pp(page)))
+ if (unlikely(PageNetpp(page)))
bad_reason = "page_pool leak";
return bad_reason;
}
^ this
This will not work they way you want it once you rebase on top of
linux-next, where we have (from mm/mm-stable)
commit 2dfcd1608f3a96364f10de7fcfe28727c0292e5d
Author: David Hildenbrand <david@xxxxxxxxxx>
Date: Fri Jul 4 12:24:58 2025 +0200
mm/page_alloc: let page freeing clear any set page type
I commented what to do already.
--
Cheers,
David / dhildenb
