From: Byungchul Park Date: Tue, 24 Feb 2026 05:13:47 +0000 (+0900) Subject: mm: introduce a new page type for page pool in page type X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=db359fccf212e7fa3136e6edbed6228475646fd7;p=thirdparty%2Fkernel%2Flinux.git mm: introduce a new page type for page pool in page type Currently, the condition 'page->pp_magic == PP_SIGNATURE' is used to determine if a page belongs to a page pool. However, with the planned removal of @pp_magic, we should instead leverage the page_type in struct page, such as PGTY_netpp, for this purpose. Introduce and 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(). Plus, add @page_type to struct net_iov at the same offset as struct page so as to use the page_type APIs for struct net_iov as well. While at it, reorder @type and @owner in struct net_iov to avoid a hole and increasing the struct size. This work was inspired by the following link: https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com/ While at it, move the sanity check for page pool to on the free path. [byungchul@sk.com: gate the sanity check, per Johannes] Link: https://lkml.kernel.org/r/20260316223113.20097-1-byungchul@sk.com Link: https://lkml.kernel.org/r/20260224051347.19621-1-byungchul@sk.com Co-developed-by: Pavel Begunkov Signed-off-by: Pavel Begunkov Signed-off-by: Byungchul Park Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Acked-by: Zi Yan Acked-by: Vlastimil Babka Reviewed-by: Toke Høiland-Jørgensen Acked-by: Mike Rapoport (Microsoft) Acked-by: Johannes Weiner Acked-by: Jakub Kicinski Acked-by: Jesper Dangaard Brouer Acked-by: Ilias Apalodimas Cc: Alexei Starovoitov Cc: Andrew Lunn Cc: Baolin Wang Cc: Brendan Jackman Cc: Christian Brauner Cc: Daniel Borkmann Cc: David S. Miller Cc: David Wei Cc: Dragos Tatulea Cc: Eric Dumazet Cc: John Fastabend Cc: Leon Romanovsky Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Mark Bloch Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mina Almasry Cc: Paolo Abeni Cc: Saeed Mahameed Cc: Simon Horman Cc: Stanislav Fomichev Cc: Stehen Rothwell Cc: Suren Baghdasaryan Cc: Taehee Yoo Cc: Tariq Toukan Cc: Usama Arif Cc: Yu Zhao Signed-off-by: Andrew Morton --- diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c index 80f9fc10877ad..7d90d2485c787 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 63d1f619260ee..c758f4e687278 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4840,10 +4840,9 @@ 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. * @@ -4878,26 +4877,6 @@ 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 - #define PAGE_SNAPSHOT_FAITHFUL (1 << 0) #define PAGE_SNAPSHOT_PG_BUDDY (1 << 1) #define PAGE_SNAPSHOT_PG_IDLE (1 << 2) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 7223f6f4e2b40..0e03d816e8b9d 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -923,6 +923,7 @@ enum pagetype { PGTY_zsmalloc = 0xf6, PGTY_unaccepted = 0xf7, PGTY_large_kmalloc = 0xf8, + PGTY_netpp = 0xf9, PGTY_mapcount_underflow = 0xff }; @@ -1055,6 +1056,11 @@ PAGE_TYPE_OPS(Zsmalloc, zsmalloc, zsmalloc) PAGE_TYPE_OPS(Unaccepted, unaccepted, unaccepted) PAGE_TYPE_OPS(LargeKmalloc, 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 a96b3e5e5574c..85e3b26ec547f 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -110,10 +110,21 @@ struct net_iov { atomic_long_t pp_ref_count; }; }; - struct net_iov_area *owner; + + unsigned int page_type; enum net_iov_type type; + struct net_iov_area *owner; }; +/* Make sure 'the offset of page_type in struct page == the offset of + * type in struct net_iov'. + */ +#define NET_IOV_ASSERT_OFFSET(pg, iov) \ + static_assert(offsetof(struct page, pg) == \ + offsetof(struct net_iov, iov)) +NET_IOV_ASSERT_OFFSET(page_type, page_type); +#undef NET_IOV_ASSERT_OFFSET + struct net_iov_area { /* Array of net_iovs for this area. */ struct net_iov *niovs; @@ -256,7 +267,7 @@ static inline unsigned long netmem_pfn_trace(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 f11f38ba2e124..fdcc2fde565b7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1043,7 +1043,6 @@ static inline bool page_expected_state(struct page *page, #ifdef CONFIG_MEMCG page->memcg_data | #endif - page_pool_page_is_pp(page) | (page->flags.f & check_flags))) return false; @@ -1070,8 +1069,6 @@ 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))) - bad_reason = "page_pool leak"; return bad_reason; } @@ -1380,9 +1377,17 @@ __always_inline bool __free_pages_prepare(struct page *page, mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); folio->mapping = NULL; } - if (unlikely(page_has_type(page))) + if (unlikely(page_has_type(page))) { + /* networking expects to clear its page type before releasing */ + if (is_check_pages_enabled()) { + if (unlikely(PageNetpp(page))) { + bad_page(page, "page_pool leak"); + return false; + } + } /* Reset the page_type (which overlays _mapcount) */ page->page_type = UINT_MAX; + } if (is_check_pages_enabled()) { if (free_page_is_bad(page)) diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h index 23175cb2bd866..3e6fde8f1726f 100644 --- a/net/core/netmem_priv.h +++ b/net/core/netmem_priv.h @@ -8,21 +8,18 @@ static inline unsigned long netmem_get_pp_magic(netmem_ref netmem) return netmem_to_nmdesc(netmem)->pp_magic & ~PP_DMA_INDEX_MASK; } -static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long pp_magic) -{ - netmem_to_nmdesc(netmem)->pp_magic |= pp_magic; -} - -static inline void netmem_clear_pp_magic(netmem_ref netmem) -{ - WARN_ON_ONCE(netmem_to_nmdesc(netmem)->pp_magic & PP_DMA_INDEX_MASK); - - netmem_to_nmdesc(netmem)->pp_magic = 0; -} - static inline bool netmem_is_pp(netmem_ref netmem) { - return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_SIGNATURE; + struct page *page; + + /* XXX: Now that the offset of page_type is shared between + * struct page and net_iov, just cast the netmem to struct page + * unconditionally by clearing NET_IOV if any, no matter whether + * it comes from struct net_iov or struct page. This should be + * adjusted once the offset is no longer shared. + */ + page = (struct page *)((__force unsigned long)netmem & ~NET_IOV); + return PageNetpp(page); } static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *pool) diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 265a729431bb7..877bbf7a19389 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -702,8 +702,18 @@ s32 page_pool_inflight(const struct page_pool *pool, bool strict) void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem) { + struct page *page; + netmem_set_pp(netmem, pool); - netmem_or_pp_magic(netmem, PP_SIGNATURE); + + /* XXX: Now that the offset of page_type is shared between + * struct page and net_iov, just cast the netmem to struct page + * unconditionally by clearing NET_IOV if any, no matter whether + * it comes from struct net_iov or struct page. This should be + * adjusted once the offset is no longer shared. + */ + page = (struct page *)((__force unsigned long)netmem & ~NET_IOV); + __SetPageNetpp(page); /* Ensuring all pages have been split into one fragment initially: * page_pool_set_pp_info() is only called once for every page when it @@ -718,7 +728,17 @@ void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem) void page_pool_clear_pp_info(netmem_ref netmem) { - netmem_clear_pp_magic(netmem); + struct page *page; + + /* XXX: Now that the offset of page_type is shared between + * struct page and net_iov, just cast the netmem to struct page + * unconditionally by clearing NET_IOV if any, no matter whether + * it comes from struct net_iov or struct page. This should be + * adjusted once the offset is no longer shared. + */ + page = (struct page *)((__force unsigned long)netmem & ~NET_IOV); + __ClearPageNetpp(page); + netmem_set_pp(netmem, NULL); }