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Mon, 28 Jul 2025 10:51:09 -0700 (PDT) MIME-Version: 1.0 References: <20250728052742.81294-1-byungchul@sk.com> <20250728082008.34091-1-byungchul@sk.com> In-Reply-To: <20250728082008.34091-1-byungchul@sk.com> From: Mina Almasry Date: Mon, 28 Jul 2025 10:50:55 -0700 X-Gm-Features: Ac12FXxVdVrRJS8-nghy7iGoNOdvPeYRQkCbX14O9WycDp4E_Y6QBKwCNMt-Clw Message-ID: Subject: Re: [PATCH v2 rebase as of Jul 28] mm, page_pool: introduce a new page type for page pool in page type To: Byungchul Park 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, 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, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 54gaxae4kdm93x3oucmegyn4thaq6jur X-Rspam-User: X-Rspamd-Queue-Id: 979451C0012 X-Rspamd-Server: rspam02 X-HE-Tag: 1753725071-807824 X-HE-Meta: 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 RFSMijPM 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 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: On Mon, Jul 28, 2025 at 1:20=E2=80=AFAM Byungchul Park w= rote: > > Rebasing on the latest linux-next/master is required. Otherwise, a > build fail is observed. Sorry about the noise. > > Changes from v1: > 1. Rebase on linux-next. > 2. Initialize net_iov->pp =3D NULL when allocating net_iov in > net_devmem_bind_dmabuf() and io_zcrx_create_area(). > 3. Use ->pp for net_iov to identify if it's pp rather than > always consider net_iov as pp. > 4. Add Suggested-by: David Hildenbrand . > > ---8<--- > From 26c9a731f388b788d6ea972c313bc8da8831412b Mon Sep 17 00:00:00 2001 > From: Byungchul Park > Date: Mon, 28 Jul 2025 17:09:20 +0900 > Subject: [PATCH v2 rebase as of Jul 28] mm, page_pool: introduce a new pa= ge 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, ->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(). > > For net_iov, use ->pp to identify if it's pp, with making sure that ->pp > is NULL for non-pp net_iov. > > This work was inspired by the following link: > > [1] https://lore.kernel.org/all/582f41c0-2742-4400-9c81-0d46bf4e8314@gmai= l.com/ > > While at it, move the sanity check for page pool to on free. > > Suggested-by: David Hildenbrand > Signed-off-by: Byungchul Park > --- > .../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 +- > io_uring/zcrx.c | 1 + > mm/page_alloc.c | 7 +++-- > net/core/devmem.c | 1 + > net/core/netmem_priv.h | 23 +++++++--------- > net/core/page_pool.c | 10 +++++-- > 9 files changed, 34 insertions(+), 45 deletions(-) > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/n= et/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 =3D mlx5e_xdpi_fifo_pop(xdpi_fifo); > page =3D 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_nmdes= c(page)->pp, > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0d4ee569aa6b..d01b296e7184 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4171,10 +4171,9 @@ int arch_lock_shadow_stack_status(struct task_stru= ct *t, unsigned long status); > * DMA mapping IDs for page_pool > * > * When DMA-mapping a page, page_pool allocates an ID (from an xarray) a= nd > - * 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 ca= nnot > + * 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 t= his > * field. > * > @@ -4205,26 +4204,6 @@ int arch_lock_shadow_stack_status(struct task_stru= ct *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_magi= c 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) =3D=3D 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 8d3fa3a91ce4..84247e39e9e7 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -933,6 +933,7 @@ enum pagetype { > PGTY_zsmalloc =3D 0xf6, > PGTY_unaccepted =3D 0xf7, > PGTY_large_kmalloc =3D 0xf8, > + PGTY_netpp =3D 0xf9, > > PGTY_mapcount_underflow =3D 0xff > }; > @@ -1077,6 +1078,11 @@ 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(netm= em_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/io_uring/zcrx.c b/io_uring/zcrx.c > index e5ff49f3425e..4cceb97ca26a 100644 > --- a/io_uring/zcrx.c > +++ b/io_uring/zcrx.c > @@ -444,6 +444,7 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *if= q, > area->freelist[i] =3D i; > atomic_set(&area->user_refs[i], 0); > niov->type =3D NET_IOV_IOURING; > + niov->pp =3D NULL; > } > > area->free_count =3D nr_iovs; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d1d037f97c5f..2f6a55fab942 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 & check_flags))) > return false; > > @@ -1069,8 +1068,6 @@ static const char *page_bad_reason(struct page *pag= e, unsigned long flags) > if (unlikely(page->memcg_data)) > bad_reason =3D "page still charged to cgroup"; > #endif > - if (unlikely(page_pool_page_is_pp(page))) > - bad_reason =3D "page_pool leak"; > return bad_reason; > } > > @@ -1379,9 +1376,11 @@ __always_inline bool free_pages_prepare(struct pag= e *page, > mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); > folio->mapping =3D NULL; > } > - if (unlikely(page_has_type(page))) > + if (unlikely(page_has_type(page))) { > + WARN_ON_ONCE(PageNetpp(page)); > /* Reset the page_type (which overlays _mapcount) */ > page->page_type =3D UINT_MAX; > + } > > if (is_check_pages_enabled()) { > if (free_page_is_bad(page)) > diff --git a/net/core/devmem.c b/net/core/devmem.c > index b3a62ca0df65..40e7a4ec9009 100644 > --- a/net/core/devmem.c > +++ b/net/core/devmem.c > @@ -285,6 +285,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, > niov =3D &owner->area.niovs[i]; > niov->type =3D NET_IOV_DMABUF; > niov->owner =3D &owner->area; > + niov->pp =3D NULL; > page_pool_set_dma_addr_netmem(net_iov_to_netmem(n= iov), > net_devmem_get_dma_= addr(niov)); > if (direction =3D=3D DMA_TO_DEVICE) > diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h > index cd95394399b4..4b90332d6c64 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_clear_lsb(netmem)->pp_magic & ~PP_DMA_INDEX_MASK; > } > > -static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned long p= p_magic) > -{ > - __netmem_clear_lsb(netmem)->pp_magic |=3D pp_magic; > -} > - > -static inline void netmem_clear_pp_magic(netmem_ref netmem) > -{ > - WARN_ON_ONCE(__netmem_clear_lsb(netmem)->pp_magic & PP_DMA_INDEX_= MASK); > - > - __netmem_clear_lsb(netmem)->pp_magic =3D 0; > -} > - > static inline bool netmem_is_pp(netmem_ref netmem) > { > - return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) =3D=3D PP_SI= GNATURE; > + /* Use ->pp for net_iov to identify if it's pp, which requires > + * that non-pp net_iov should have ->pp NULL'd. > + */ > + if (netmem_is_net_iov(netmem)) > + return !!__netmem_clear_lsb(netmem)->pp; > + > + /* For system memory, page type bit in struct page can be used > + * to identify if it's pp. > + */ > + return PageNetpp(__netmem_to_page(netmem)); > } > > static inline void netmem_set_pp(netmem_ref netmem, struct page_pool *po= ol) > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 05e2e22a8f7c..0a10f3026faa 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -654,7 +654,6 @@ 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); > > /* Ensuring all pages have been split into one fragment initially= : > * page_pool_set_pp_info() is only called once for every page whe= n it > @@ -665,12 +664,19 @@ void page_pool_set_pp_info(struct page_pool *pool, = netmem_ref netmem) > page_pool_fragment_netmem(netmem, 1); > if (pool->has_init_callback) > pool->slow.init_callback(netmem, pool->slow.init_arg); > + > + if (netmem_is_net_iov(netmem)) > + return; > + __SetPageNetpp(__netmem_to_page(netmem)); nit: if (!netmem_is_net_iov(netmem)) __SetPageNetpp(__netmem_to_page(netmem)); i.e. no need for the early return. I would also move the diff to replace netmem_or_pp_magic. > } > > void page_pool_clear_pp_info(netmem_ref netmem) > { > - netmem_clear_pp_magic(netmem); > netmem_set_pp(netmem, NULL); > + > + if (netmem_is_net_iov(netmem)) > + return; > + __ClearPageNetpp(__netmem_to_page(netmem)); Same here. I would do: if (!netmem_is_net_iov(netmem)) __ClearPageNetpp(__netmem_to_page(netmem)); and no need for the early return. Reviewed-by: Mina Almasry --=20 Thanks, Mina