From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 700D1341AA; Fri, 25 Jul 2025 00:26:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753403199; cv=none; b=Y8Y7KwYrnEcEmI5P1tOXLDcKT62vMRIv3ozFVO8DDHQJK6IUjZz6pyNGFIrd/83Fd8BFoh5vw0+pnUX8NnNzvMeMV9YeasGf6WeKLEY9z8I+wLBhGLSeyP99VrBZuY8ujtG4XB5/JZ2UgmLUejmZtZ4GJwZvbotb0ki6/ZetEEo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753403199; c=relaxed/simple; bh=agpv9S9Mak0o5aKUB9hyX3H8IhS+yjKewsgU+wSUly4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=b10dT4L4JQnLE+nKC0g47DdPWfFCfEz4A/e9/dBVsBsEK6WBf8UxrDFo3Dvc9nMO2sGvriy90aQSWFlBqbd0qINcTLomCOui9Q0os7g6jLzbI1HNEDcEBazt9K6vTWDQ29kTUn3BFwwERkkZFg+Xsc8rizpcfZ0jCxo0iXEEu4Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-681ff7000002311f-cb-6882cf2f93ac Date: Fri, 25 Jul 2025 09:26:18 +0900 From: Byungchul Park To: Mina Almasry 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 Subject: Re: [PATCH] mm, page_pool: introduce a new page type for page pool in page type Message-ID: <20250725002618.GA11321@system.software.com> References: <20250721054903.39833-1-byungchul@sk.com> <20250723044610.GA80428@system.software.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa1BMYRjHvXvOnnNarTltyiszjG1oZERk5nGZ5Ns74zIMPmAMOzrs0s2W aplm1mrIUnJnW2wuqURsqTbVqK1cGlNWy1KJbj4grDS2bWK3GH37zf953+f3//BwlOy5OIhT xSUJ6jhFjJyR0JIvvrnz5jfrlAsq7XPBWFzEwO1fqXDrfYUYjIVlCAZcbSz8rm5E8KP+MQOf rE4E13MHKTA2p9Pws3iIgt7GLhZum9dAZ14fDVVHyynoOvmEgcx0NwXVrn4WdBX5IjCWaFlo KcsSw9mhmxSUa9+z8LLSyMC7ot9i6KvLpOGpoYCGb+fqKejMioJGUyAMNn1GUF9cLoLBE5cZ sF+qFMEZm4mB7vROBDZrFw3nhjMYyDmUhcD9y7OtP3tADDkN79ioUGL9/JUipQVvRMRR80xE LIYOlpjM+0lJfijRO2wUMRceY4jZeZol7a+qGPLkopsmlg9LiKXih4hkHu5nyPfetzT5WmNn 1vlvkSyPFmJUyYJ6fuQOibLW1YgS2jenjvR1i7XofpQe+XCYj8BNd44x/7jKbWX1iONofhYe erbCGzN8CHY4XJSXJ/Nz8I2aU2IvU/x5Fl8/MsnL/vwW3KKtFnlZygPWZbtH38h4J8INRQlj uR9+eqmHHvsbgoev2CiviuKn4Vsj3Fg8Ax9+kDOq8uHX45IC/WizAD4YPyp77Fkv8bTs4fDx R21/K0/FtfkOOhv5GcYpDOMUhv8KwziFCdGFSKaKS45VqGIiwpSaOFVq2M74WDPyHFle2vDW CuRs2VCHeA7JfaUkRKeUiRXJiZrYOoQ5Sj5Z2nbPE0mjFZoDgjp+u3p/jJBYh6ZxtHyKdOFg SrSM361IEvYKQoKg/jcVcT5BWqRxLNs4vTM6zHDeVxO5Psj+Zunaia4UY1pDU8Oe7tIVpXNn t0f4536Z2WG9cyEkj7+6a3EHXnmyqNWyr+rGalXk0pVLdlpsZ16k2Pjg1qMB+tno4/dTmp7U gJzcn6En8jvA+XDbLl1GUvzdkT0TAux4+aYEv0WBM8INqw4KGQPXal/L6USlIjyUUicq/gAl 8aVOYAMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA02Se0hTcRTH+d230uS2rC5FFIuwDLOo4NjDpKB+BPagKJJAR17acE67S3FB sVR6SJrae1u10ExttJz5qinldGYFimFZmaY2CSwtU3FuZS6J/O/D95zz+f5zOFJuoxdwau1x UdIqNQomkArctTEjLLwlXbXa9G0WmG1WBu6Pp8G9T9U0mEsrEYx4PrAwWetC8LOhiYEB5zCC gjtjJJhbMikYtU2Q4Hb1snDfHg3dRf0UOM5WkdB78TkD2ZleEmo9gyykVxcTYC43sOC82UxD a2UODZcn7pJQZfjEwuvHZga6rJM09NdnU9BsLKHg+5UGErpzosBlmQdjL78iaLBVETB24SYD 7TceE3CpzcJAX2Y3gjZnLwVXfOcYMJ3OQeAdn7IN5o7QYGrsYqNWYufXIRI/KnlH4I66FwSu MX5kscWegsuLQ3FWRxuJ7aXnGWwfzmdx5xsHg59f91K4picC11T/JHB2xiCDf7jfU3iorp3Z ExwTuCle1KhTRSk8Mi5Q9czjQsmdh9J+9/fRBlQWlYUCOIFfJzi8TjYLcRzFLxMmXmzxxwwf InR0eEg/B/MrhMK6PNrPJH+VFQrOBPl5Dh8jtBpqCT/LeBDSc71/d+T8MBIarcnT+Wyh+cZn avo2RPDdaiP9VSS/ULj3m5uOFwsZFaa/VQH8XqG8JIvx81x+qfC0sonIRUHGGSbjDJPxv8k4 w2RBVCkKVmtTE5VqzfpVugSVXqtOW3UkKdGOpt6o6KQvrxqNvN5Rj3gOKWbJcEi6Sk4rU3X6 xHokcKQiWPbh4VQki1fqT4hSUqyUohF19WghRynmy3YeFOPk/FHlcTFBFJNF6d+U4AIWGND2 24vaW38V6p/tcy/O2+8wDIXuKN45UGkNO7UkQvugaXJ08/jguSpv6RuJjO5bn29JKNBo2+W8 pzemMcEdaXf8mLN7g1SkXFeRv20Pv/xsRNmT74c/d3I9sXlWaeumtYmjTfNerbw4MPuAz0DJ LkXH2VwT14K+9Kxd/Xa489iKA5EKSqdSrgklJZ3yD3IX9RFCAwAA X-CFilter-Loop: Reflected On Thu, Jul 24, 2025 at 02:23:05PM -0700, Mina Almasry wrote: > On Tue, Jul 22, 2025 at 9:46 PM Byungchul Park wrote: > > > > On Tue, Jul 22, 2025 at 03:17:15PM -0700, Mina Almasry wrote: > > > On Sun, Jul 20, 2025 at 10:49 PM 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 free. > > > > > > > > Byungchul > > > > > > > > ---8<--- > > > > From 7d207a1b3e9f4ff2a72f5b54b09e3ed0c4aaaca3 Mon Sep 17 00:00:00 2001 > > > > From: Byungchul Park > > > > Date: Mon, 21 Jul 2025 14:05:20 +0900 > > > > Subject: [PATCH] mm, page_pool: introduce a new page 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, page type e.i. PGTY_netpp can be used > > > > 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/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 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 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. > > > > * > > > > @@ -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_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 > > > > - > > > > #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 = 0xf6, > > > > PGTY_unaccepted = 0xf7, > > > > PGTY_large_kmalloc = 0xf8, > > > > + PGTY_netpp = 0xf9, > > > > > > > > PGTY_mapcount_underflow = 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 page *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 *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))) > > > > + if (unlikely(PageNetpp(page))) > > > > bad_reason = "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(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 pp_magic) > > > > -{ > > > > - __netmem_clear_lsb(netmem)->pp_magic |= 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 = 0; > > > > -} > > > > - > > > > static inline bool netmem_is_pp(netmem_ref netmem) > > > > { > > > > - return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_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 == 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=NULL in the > > > non-pp case and pp=non 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. Totally Agree. Lemme try your option #1 then. Byungchul > > > -- > Thanks, > Mina