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166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761205498; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=lyaLQ+gYFf6FLMP+MiLbS2IZ4+W485nU1ADqrG7+vE4=; b=6zLrsuEk55BY5izA2/u6XvoodG/Hfz5V5SFYOQGX9eohstKEsQwRingP5XbUXXF0z1Hb1N 5cUpGclY/bg+T3ku6sGML3KgKFLLZL8r8PxxD0PhbgSsh8fN5E9LI5ZBtaFvHgtB09ObYd NLAz0IxQLtrOQo73wRQOwzV5TVp3gb8= X-AuditID: a67dfc5b-c2dff70000001609-d6-68f9dcf85542 From: Byungchul Park To: linux-mm@kvack.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, 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: [RFC mm v4 2/2] mm: introduce a new page type for page pool in page type Date: Thu, 23 Oct 2025 16:44:10 +0900 Message-Id: <20251023074410.78650-3-byungchul@sk.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20251023074410.78650-1-byungchul@sk.com> References: <20251023074410.78650-1-byungchul@sk.com> 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I6KBD4YGfwCEeV51yUIwdbeRx5K9/+iBj/9E5jAL1NN+cd++cLl4lxLpbT4FszdtEgeFgNMBRgHRcRYuK4uyC/LV12sQ6pMwC2v6Sw++egMO0PUejYYIOQ5aakx/Syqg92GdaJv8tXPBFuMRRF37AE2jDOmVBMGy2pwSXOxek7C5vgUqwn4eyZ1WdHGJI/aZ138SNQp69CU3d4I0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: ->pp_magic field in struct page is current used to identify if a page belongs to a page pool. However, ->pp_magic will be removed and page type bit in struct page e.i. PGTY_netpp can be used for that 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(). This work was inspired by the following link: [1] https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com/ While at it, move the sanity check for page pool to on free. Suggested-by: David Hildenbrand Co-developed-by: Pavel Begunkov Signed-off-by: Pavel Begunkov Signed-off-by: Byungchul Park Acked-by: David Hildenbrand Acked-by: Zi Yan --- Hi Mina, I dropped your Reviewed-by tag since there are updates on some comments in network part. Can I still keep your Reviewed-by? Byungchul --- .../net/ethernet/mellanox/mlx5/core/en/xdp.c | 2 +- include/linux/mm.h | 27 +++---------------- include/linux/page-flags.h | 6 +++++ include/net/netmem.h | 2 +- mm/page_alloc.c | 8 +++--- net/core/netmem_priv.h | 17 +++--------- net/core/page_pool.c | 14 +++++----- 7 files changed, 25 insertions(+), 51 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 b6fdf3557807..f5155f1c75f5 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -4361,10 +4361,9 @@ 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. * @@ -4399,26 +4398,6 @@ 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..0ec4c7561081 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -260,7 +260,7 @@ 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 fb91c566327c..c69ed3741bbc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1042,7 +1042,6 @@ 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; @@ -1069,8 +1068,6 @@ 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; } @@ -1379,9 +1376,12 @@ __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 5561fd556bc5..664a9fe87c66 100644 --- a/net/core/netmem_priv.h +++ b/net/core/netmem_priv.h @@ -8,18 +8,6 @@ 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) { /* net_iov may be part of a page pool. For net_iov, ->pp in @@ -30,7 +18,10 @@ static inline bool netmem_is_pp(netmem_ref netmem) if (netmem_is_net_iov(netmem)) return !!netmem_to_nmdesc(netmem)->pp; - return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_SIGNATURE; + /* For system memory, page type in struct page can be used to + * determine if the pages belong to a page pool. + */ + return PageNetpp(__netmem_to_page(netmem)); } 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 2756b78754b0..c43a0f4479d4 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -700,12 +700,11 @@ void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem) { netmem_set_pp(netmem, pool); - /* For page-backed, pp_magic is used to identify if it's pp. - * For net_iov, it's ensured nmdesc->pp is non-NULL if it's pp - * and nmdesc->pp is NULL if it's not. + /* For system memory, page type in struct page is used to + * determine if the pages belong to a page pool. */ if (!netmem_is_net_iov(netmem)) - netmem_or_pp_magic(netmem, PP_SIGNATURE); + __SetPageNetpp(__netmem_to_page(netmem)); /* Ensuring all pages have been split into one fragment initially: * page_pool_set_pp_info() is only called once for every page when it @@ -720,12 +719,11 @@ void page_pool_set_pp_info(struct page_pool *pool, netmem_ref netmem) void page_pool_clear_pp_info(netmem_ref netmem) { - /* For page-backed, pp_magic is used to identify if it's pp. - * For net_iov, it's ensured nmdesc->pp is non-NULL if it's pp - * and nmdesc->pp is NULL if it's not. + /* For system memory, page type in struct page is used to + * determine if the pages belong to a page pool. */ if (!netmem_is_net_iov(netmem)) - netmem_clear_pp_magic(netmem); + __ClearPageNetpp(__netmem_to_page(netmem)); netmem_set_pp(netmem, NULL); } -- 2.17.1