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d=hostedemail.com; t=1762933290; a=rsa-sha256; cv=none; b=p9XXjxm/++//sk5q7aFlU8+wBoKkp/4Vp7jODQrSjfl7G0/q9wCGNOPF7HYgWaNQbvbti6 S/0h8M6ukCM5IklLrFuvGpaeW63RD/YEho5hkPXAL8Yw2x8VyFoNRmqVsRsi227TUDzu2Q 5Zt7WuUUgJgrnfHb5x6hydtPaPEGT5o= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf28.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-c2dff70000001609-5a-69143a24e040 Date: Wed, 12 Nov 2025 16:41:18 +0900 From: Byungchul Park To: Jakub Kicinski Cc: linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, almasrymina@google.com, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, sfr@canb.auug.org.au, dw@davidwei.uk, ap420073@gmail.com, dtatulea@nvidia.com Subject: Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as page pool for net_iov not page-backed Message-ID: <20251112074118.GA31149@system.software.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> <20251106173320.2f8e683a@kernel.org> <20251107015902.GA3021@system.software.com> <20251106180810.6b06f71a@kernel.org> <20251107044708.GA54407@system.software.com> <20251107174129.62a3f39c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; 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Can we not move owner > to _pp_mapping_pad ? Or reorder it with type, enum net_iov_type > only has 2 values we can smoosh it with page_type easily. At the beginning I tried to smoosh it with page_type but it requires the additional logic or something to save and restore the value of enum net_iov_type if the netmem is net_iov when updating page_type like: if (netmem_is_net_iov(netmem)) type = get_type_from_niov(netmem_to_niov(netmem)); /* Unconditionally clear the value of enum net_iov_type. */ __{Set,Clear}PageNetpp(__netmem_to_page((__force unsigned long)netmem & ~NET_IOV)); if (netmem_is_net_iov(netmem)) set_type_to_niov(netmem_to_niov(netmem), type); Or page_pool_{set,clear}_pp_info() callers should handle it in a similar way. I'd like to check if you are okay with this approach. Or I can make it simpler by adding page_type to struct net_iov like the following. Jakub, do these approachs work for you? Byungchul --- 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 a3f97c551ad8..081e365caa1a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4252,10 +4252,9 @@ 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. * @@ -4290,26 +4289,6 @@ 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 0091ad1986bf..edf5418c91dd 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -934,6 +934,7 @@ enum pagetype { PGTY_zsmalloc = 0xf6, PGTY_unaccepted = 0xf7, PGTY_large_kmalloc = 0xf8, + PGTY_netpp = 0xf9, PGTY_mapcount_underflow = 0xff }; @@ -1078,6 +1079,11 @@ 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 651e2c62d1dd..b42d75ecd411 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -114,10 +114,21 @@ struct net_iov { atomic_long_t pp_ref_count; }; }; + + unsigned int page_type; struct net_iov_area *owner; enum net_iov_type type; }; +/* 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; @@ -260,7 +271,7 @@ 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 600d9e981c23..01dd14123065 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1041,7 +1041,6 @@ 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; @@ -1068,8 +1067,6 @@ 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; } @@ -1378,9 +1375,12 @@ __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 */ + WARN_ON_ONCE(PageNetpp(page)); /* 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 23175cb2bd86..6b7d90b8ebb9 100644 --- a/net/core/netmem_priv.h +++ b/net/core/netmem_priv.h @@ -8,21 +8,15 @@ 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; + /* 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. + */ + return PageNetpp(__netmem_to_page((__force unsigned long)netmem & ~NET_IOV)); } 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 1a5edec485f1..27650ca789d1 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -699,7 +699,14 @@ s32 page_pool_inflight(const struct page_pool *pool, bool strict) void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem) { 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. + */ + __SetPageNetpp(__netmem_to_page((__force unsigned long)netmem & ~NET_IOV)); /* Ensuring all pages have been split into one fragment initially: * page_pool_set_pp_info() is only called once for every page when it @@ -714,7 +721,14 @@ 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); + /* 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. + */ + __ClearPageNetpp(__netmem_to_page((__force unsigned long)netmem & ~NET_IOV)); + netmem_set_pp(netmem, NULL); }