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Thu, 24 Jul 2025 14:23:18 -0700 (PDT) MIME-Version: 1.0 References: <20250721054903.39833-1-byungchul@sk.com> <20250723044610.GA80428@system.software.com> In-Reply-To: <20250723044610.GA80428@system.software.com> From: Mina Almasry Date: Thu, 24 Jul 2025 14:23:05 -0700 X-Gm-Features: Ac12FXz-gExQLTDVuATyXHwkSGv0B-njaHRD7KrjKadlfvJJk-4Hay1UO-wB7MU Message-ID: Subject: Re: [PATCH] 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-Rspamd-Queue-Id: 459C1C0006 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: nbcfec3yiazo1y8x1sum1zfh9mr1kjqy X-HE-Tag: 1753392200-445363 X-HE-Meta: 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 Kbn+m3L8 cwWQErs2k+cvNLW2jrEj30HAhqB4ZJvX3pW1lCtex3QfefUde8lQJWONZQ/Pk09s1wVekFwqrMQSmGBKsYOfYTQbP0XWCHlZdTvoTf0yuZSd05gkGKYEfLLynY2/9utaid1bRkZDJDwwh/CkWRius9+L1WtluMCwJ6YtmkAsjLqjlCp1qNcBrJy6AD0duVerkfiTfcojebIshnYrjvalA7CIreZiQLUlRHAVN4WB1jhn9TEzxAKE/86myYG6taGG83JW/QZ8M7DPo2LhPs1iTyAh3BFKfEz9YTQpzCb/wugTANgpaMLjP/bKRFJNfxbhGGUkWWEF8SRL3sPSUs29d4NwwHTWXKy6CTXhNz82ENJh/BBUT0JFusmjK+6L/6ONT6lIaOS1WZ7VNTF10o5UT9HNuELc38dnR0D72hRHx7nB6SPdRI72LjXZoVU0PXQ86AJxy04dLAiH/are3tm7DyCzNIxRDXbGTkSxvatYcu1GAgHM= 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 Tue, Jul 22, 2025 at 9:46=E2=80=AFPM Byungchul Park w= rote: > > On Tue, Jul 22, 2025 at 03:17:15PM -0700, Mina Almasry wrote: > > On Sun, Jul 20, 2025 at 10:49=E2=80=AFPM 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 fr= ee. > > > > > > Byungchul > > > > > > ---8<--- > > > From 7d207a1b3e9f4ff2a72f5b54b09e3ed0c4aaaca3 Mon Sep 17 00:00:00 200= 1 > > > From: Byungchul Park > > > Date: Mon, 21 Jul 2025 14:05:20 +0900 > > > Subject: [PATCH] mm, page_pool: introduce a new page type for page po= ol 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 us= ed > > > 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@= gmail.com/ > > > > > > Suggested-by: Pavel Begunkov > > > Signed-off-by: Byungchul Park > > > --- > > > .../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/drive= rs/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_xd= psq *sq, > > > xdpi =3D mlx5e_xdpi_fifo_pop(xdpi_fif= o); > > > 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_n= mdesc(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 xarra= y) 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_p= p()). 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 w= e 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 (s= ince > > > + * it overlaps with page->lru.next), so we must ensure that we canno= t > > > * mistake a valid kernel pointer with any of the values we write in= to 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_S= HIFT - 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) =3D=3D 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 =3D 0xf6, > > > PGTY_unaccepted =3D 0xf7, > > > PGTY_large_kmalloc =3D 0xf8, > > > + PGTY_netpp =3D 0xf9, > > > > > > PGTY_mapcount_underflow =3D 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 pag= e *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 *p= age, 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))) > > > + if (unlikely(PageNetpp(page))) > > > bad_reason =3D "page_pool leak"; > > > return bad_reason; > > > } > > > diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h > > > index cd95394399b4..39a97703d9ed 100644 > > > --- a/net/core/netmem_priv.h > > > +++ b/net/core/netmem_priv.h > > > @@ -8,21 +8,11 @@ static inline unsigned long netmem_get_pp_magic(net= mem_ref netmem) > > > return __netmem_clear_lsb(netmem)->pp_magic & ~PP_DMA_INDEX_M= ASK; > > > } > > > > > > -static inline void netmem_or_pp_magic(netmem_ref netmem, unsigned lo= ng pp_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_IN= DEX_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 P= P_SIGNATURE; > > > + if (netmem_is_net_iov(netmem)) > > > + return true; > > > > As Pavel alludes, this is dubious, and at least it's difficult to > > reason about it. > > > > There could be net_iovs that are not attached to pp, and should not be > > treated as pp memory. These are in the devmem (and future net_iov) tx > > paths. > > > > We need a way to tell if a net_iov is pp or not. A couple of options: > > > > 1. We could have it such that if net_iov->pp is set, then the > > netmem_is_pp =3D=3D true, otherwise false. > > 2. We could implement a page-flags equivalent for net_iov. > > > > Option #1 is simpler and is my preferred. To do that properly, you need= to: > > > > 1. Make sure everywhere net_iovs are allocated that pp=3DNULL in the > > non-pp case and pp=3Dnon NULL in the pp case. those callsites are > > net_devmem_bind_dmabuf (devmem rx & tx path), io_zcrx_create_area > > (io_uring rx path). > > > > 2. Change netmem_is_pp to check net_iov->pp in the net_iov case. > > Good idea, but I'm not sure if I could work on it without consuming your > additional review efforts. Can anyone add net_iov_is_pp() helper? > Things did indeed get busy for me with work work the past week and I still need to look at your merged netmem desc series, but I'm happy to review whenever I can. > Or use the page type, Netpp, as an additional way to identify if it's a > pp page for system memory, keeping the current way using ->pp_magic. > So the page type, Netpp, is used for system memory, and ->pp_magic is > used for net_iov. The clean up for ->pp_magic can be done if needed. > IMO I would like to avoid deviations like this, especially since ->pp_magic is in the netmem_desc struct that is now shared between page and net_iov. I'd rather both use pp_magic or both not, but that may just be me. --=20 Thanks, Mina