From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A40BCC83F1B for ; Thu, 17 Jul 2025 03:09:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 424BC8D0007; Wed, 16 Jul 2025 23:09:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3D5078D0001; Wed, 16 Jul 2025 23:09:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2C3848D0007; Wed, 16 Jul 2025 23:09:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 172FD8D0001 for ; Wed, 16 Jul 2025 23:09:11 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 95AA61DA91D for ; Thu, 17 Jul 2025 03:09:10 +0000 (UTC) X-FDA: 83672275260.14.6EF7A20 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by imf21.hostedemail.com (Postfix) with ESMTP id 06B591C0009 for ; Thu, 17 Jul 2025 03:09:07 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; spf=pass (imf21.hostedemail.com: domain of byungchul@sk.com designates 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=1752721748; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JGZ/1Og0czLznV+mlPk7Sjk/Sg2KLk4Z7sVVdK9QVzQ=; b=QpOmYjs8k0/ehmR0JvemaKv7K5RMjZchjLn94CoC2F3zT+tILn6Ct8DQbnBQIXnpDOcXBB 732706AbLiucAN74ko5QC9OWHuFsdtEs3VwZZIfB1Z9EiGMjRgOfYDCsDJ1bQKVDaex1je pzMHI8NZvcizD4BVSHw+KDv2Z5NGmAU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1752721749; a=rsa-sha256; cv=none; b=zn8AtKNBr0RCR1GiMZFsApa+U3EDYgS5O85nJdaob1xKb0OXX+m+gy7BH2sfwjLbAmW0dS P5KwblP9CVZlr4hJCYMV7h/AMs75Zpy49SGEtlaCcOsa7oZE2nEL1GJ0tKW7YtDGfAUPdm CCmLQH7agy3bSfLWrhugDrP8sPAAn74= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf21.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-681ff7000002311f-57-6878694f2f10 Date: Thu, 17 Jul 2025 12:08:58 +0900 From: Byungchul Park To: Pavel Begunkov Cc: Mina Almasry , David Hildenbrand , "willy@infradead.org" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, kuba@kernel.org, ilias.apalodimas@linaro.org, harry.yoo@oracle.com, hawk@kernel.org, akpm@linux-foundation.org, davem@davemloft.net, john.fastabend@gmail.com, andrew+netdev@lunn.ch, toke@redhat.com, tariqt@nvidia.com, edumazet@google.com, pabeni@redhat.com, saeedm@nvidia.com, leon@kernel.org, ast@kernel.org, daniel@iogearbox.net, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, vishal.moola@gmail.com, hannes@cmpxchg.org, ziy@nvidia.com, jackmanb@google.com Subject: Re: [PATCH net-next v9 3/8] page_pool: access ->pp_magic through struct netmem_desc in page_pool_page_is_pp() Message-ID: <20250717030858.GA26168@system.software.com> References: <20250710082807.27402-1-byungchul@sk.com> <20250710082807.27402-4-byungchul@sk.com> <20250711011435.GC40145@system.software.com> <582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <582f41c0-2742-4400-9c81-0d46bf4e8314@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+e+cnXNcDv6tsr8VgasIlOyCH17SrIjg0B2iLxXl1EMbzWWz dBOtVUI20jK7zgWTzGwaqyVzSVot0yRhscjWzdVMQzTN28hMzaNEfnt43uf58X54OEpxVbqA 0+iOCXqdSqtkZLTsR3jpip0ag3qVyb8SrI4qBip/GeDOF7cUrHYXgqGRjywMNjQxcKs0RIHV m0fDsOM3BR2NQRYqndshUN5Jw+OzNRQEL7xkoCBvlIK6kV4WTrsrJPDaVSiFy79vU1Bj+sLC m1orA21VE1Lo9BTQ0Gy5S0OgcAM02iIg9KoHQYOjRgKh8zcZKPbZGGjPCyDwPQ/SUHKqEIGj 3i+F0V+TjJIXbeyGpfzznj6Kr777XsI/snxmeZvzOP+wIpo3+30U77SfY3jnwCWW/9T6mOFf Xh+l+UfuQQlfcKaX4fs7PtB8X/1bhndUv6X5FlsDu2v2XllCqqDVZAr6lYlJMrW7KESnl603 lNaW0CZUv8qMOI7gOFLsjjOjsCn59FofI9o0XkY89hWizeDlxO8foUQ9F8eQ7nceVtQUfseQ cmeiGJ+DDcT+aqopx0B8Y3vNSMYpsFlCHP3dUjEux7NJ841v9HQ1mvjHuyRinsILyZ1xTrTD 8Dpiqeuaos/DS8hTV5NE5BDs5sjlsjLp9JeR5FmFn76IsGUG1jIDa/mPtSHKjhQaXWaaSqON i1UbdRpDbMqRNCeaXEt57p99bjTwercHYQ4pw+VJ97PUCqkqM8OY5kGEo5Rz5cW+TLVCnqoy Zgv6Iwf1x7VChgct5GjlfPmaUFaqAh9SHRMOC0K6oP93lXBhC0zoKK7d49JpmqxRmybWGmcl DjQuTqYSwnMeNDyJNy3aHxiuunVg6OSWXO1a/VBXtTLqe7N3oyUpR5MSolq0Eds+umIsV53X o0uftHgvjM2v3J5a5D0U4/BmByPb6zbHRMV/HdPHng4k5LfuS95R2Lo1+LN+64l7csFn3CXL 97snrijpDLVqdTSlz1D9BfwjHZcpAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+59zdnZcDY7L8jSFYiGBkhoZvHSxUZF/BLtAENSHHHloS121 6ZxBZDoq56XsgrUtWlSzLWGxZE5T02leEDIm5krLWhaVknmlua4ror49PO/v93x6GVISpKSM Sp3Ha9SKHBktokQ7NpSs3qnSK5MfP4gFi7OWhrtf9FDzyiMAi8ONYCY4JITpji4abt6YI8HS Z6Bg1jlPwtvOgBDuujJgxPaOgqYz9SQEznXTUGEIkdAc/CSEYs8dAtqv9QjgibtSAJfmb5NQ X/RKCP2NFhpe1v4QwDtvBQU9JjsFI5Vy6LQuhbnecQQdznoC5sqv0XDRZ6XhjWEEga89QIH5 VCUCZ4tfAKEvvzbMj14K5XG4fXyCxHX2ZwRuML0QYqsrH9+/E4+Nfh+JXY5SGrumLgjx8NMm GndfCVG4wTNN4IqSTzSefPucwhMtAzS++f4zgZ11A9QuyT7Rxiw+R6XjNUmpmSKlp2qOOnpr s/5Go5kqQi3JRhTBcGwK11o9QRsRw1BsHOd1rA7XNLuK8/uDZDhHsQnc2KBXGM4kO0hzNldq GF/M6jlH729TzALn+7bPiESMhDUSnHNyTBDGxWwk13N1lPqjxnP+7x+IME+yMVzNdyZcR7Cb OFPzh9/rS9iVXKu7iziPxKb/bNN/tumfbUWkA0Wp1LpchSpnXaI2W1moVukTDx7JdaFfD2E7 8bXKg2b607yIZZBskTjzXoFSIlDotIW5XsQxpCxKfNGnU0rEWYrC47zmyAFNfg6v9aIYhpJF i9P38pkS9pAij8/m+aO85u+VYCKkRehh3NfLeR3BVQ0xw9qgQR/oGPuoXtD8se16mX3gpGp/ 9/LW8t3VoWPbl/f0Vc3LY+tN9jTT+tJvsPF0+miG0bhiPHqh133G1iZ9oA+dlR9OS1pWMHp1 6zbvdLK8+DRRNvR6uE4q2zJ4YjCxPHLaPNUPblxQmzK73Z8AgeiRPWtllFapWBNParSKn16C 57gMAwAA X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 06B591C0009 X-Stat-Signature: 8gojbi8z7nrciz1je8asni1eg5azbm64 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1752721747-841757 X-HE-Meta: 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 XJJzHjY+ aTjXErHXdXwbTodrpsUFi5YuKlieAv8pw5oNjpIrzN/5vPIfCBDi22f6Hx9NFTPaLQYpcpOlFBNdwftaqcmwYBwXlFtDFi05xmAu53S51x08Tsi8nkOLGGDEMErEEwMtJYL0IdVcS4S7D+Pk= 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 Sat, Jul 12, 2025 at 02:58:14PM +0100, Pavel Begunkov wrote: > On 7/11/25 02:14, Byungchul Park wrote: > ...>>> +#ifdef CONFIG_PAGE_POOL > > > > +/* XXX: This would better be moved to mm, once mm gets its way to > > > > + * identify the type of page for page pool. > > > > + */ > > > > +static inline bool page_pool_page_is_pp(struct page *page) > > > > +{ > > > > + struct netmem_desc *desc = page_to_nmdesc(page); > > > > + > > > > + return (desc->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE; > > > > +} > > > > > > pages can be pp pages (where they have pp fields inside of them) or > > > non-pp pages (where they don't have pp fields inside them, because > > > they were never allocated from the page_pool). > > > > > > Casting a page to a netmem_desc, and then checking if the page was a > > > pp page doesn't makes sense to me on a fundamental level. The > > > netmem_desc is only valid if the page was a pp page in the first > > > place. Maybe page_to_nmdesc should reject the cast if the page is not > > > a pp page or something. > > > > Right, as you already know, the current mainline code already has the > > same problem but we've been using the werid way so far, in other words, > > mm code is checking if it's a pp page or not by using ->pp_magic, but > > it's ->lur, ->buddy_list, or ->pcp_list if it's not a pp page. > > > > Both the mainline code and this patch can make sense *only if* it's > > actually a pp page. It's unevitable until mm provides a way to identify > > the type of page for page pool. Thoughts? > Question to mm folks, can we add a new PGTY for page pool and use > that to filter page pool originated pages? Like in the incomplete > and untested diff below? > > > commit 8fc2347fb3ff4a3fc7929c70a5a21e1128935d4a > Author: Pavel Begunkov > Date: Sat Jul 12 14:29:52 2025 +0100 > > net/mm: use PGTY for tracking page pool pages > > Currently, we use page->pp_magic to determine whether a page belongs to > a page pool. It's not ideal as the field is aliased with other page > types, and thus needs to to rely on elaborated rules to work. Add a new > page type for page pool. Hi Pavel, I need this work to be done to remove ->pp_magic in struct page. Will you let me work on this work? Or can you please refine and post this work? If you let me, I will go for this as a separate patch from this series. Byungchul > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0ef2ba0c667a..975a013f1f17 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4175,7 +4175,7 @@ int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status); > #ifdef CONFIG_PAGE_POOL > static inline bool page_pool_page_is_pp(struct page *page) > { > - return (page->pp_magic & PP_MAGIC_MASK) == PP_SIGNATURE; > + return PageNetpp(page); > } > #else > static inline bool page_pool_page_is_pp(struct page *page) > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 4fe5ee67535b..9bd1dfded2fc 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 de1d95f04076..20f5dbb08149 100644 > --- a/include/net/netmem.h > +++ b/include/net/netmem.h > @@ -113,6 +113,8 @@ static inline bool netmem_is_net_iov(const netmem_ref netmem) > */ > static inline struct page *__netmem_to_page(netmem_ref netmem) > { > + DEBUG_NET_WARN_ON_ONCE(netmem_is_net_iov(netmem)); > + > return (__force struct page *)netmem; > } > > diff --git a/net/core/netmem_priv.h b/net/core/netmem_priv.h > index cd95394399b4..e38c64da1a78 100644 > --- a/net/core/netmem_priv.h > +++ b/net/core/netmem_priv.h > @@ -13,16 +13,11 @@ 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; > + return page_pool_page_is_pp(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 05e2e22a8f7c..52120e2912a6 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -371,6 +371,13 @@ struct page_pool *page_pool_create(const struct page_pool_params *params) > } > EXPORT_SYMBOL(page_pool_create); > > +static void page_pool_set_page_pp_info(struct page_pool *pool, > + struct page *page) > +{ > + __SetPageNetpp(page); > + page_pool_set_pp_info(page_to_netmem(page)); > +} > + > static void page_pool_return_netmem(struct page_pool *pool, netmem_ref netmem); > > static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool) > @@ -534,7 +541,7 @@ static struct page *__page_pool_alloc_page_order(struct page_pool *pool, > } > > alloc_stat_inc(pool, slow_high_order); > - page_pool_set_pp_info(pool, page_to_netmem(page)); > + page_pool_set_page_pp_info(pool, page); > > /* Track how many pages are held 'in-flight' */ > pool->pages_state_hold_cnt++; > @@ -579,7 +586,7 @@ static noinline netmem_ref __page_pool_alloc_netmems_slow(struct page_pool *pool > continue; > } > > - page_pool_set_pp_info(pool, netmem); > + page_pool_set_page_pp_info(pool, __netmem_to_page(netmem)); > pool->alloc.cache[pool->alloc.count++] = netmem; > /* Track how many pages are held 'in-flight' */ > pool->pages_state_hold_cnt++; > @@ -654,7 +661,6 @@ 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 when it > @@ -669,7 +675,6 @@ 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); > netmem_set_pp(netmem, NULL); > } > > @@ -730,8 +735,11 @@ static void page_pool_return_netmem(struct page_pool *pool, netmem_ref netmem) > trace_page_pool_state_release(pool, netmem, count); > > if (put) { > + struct page *page = netmem_to_page(netmem); > + > page_pool_clear_pp_info(netmem); > - put_page(netmem_to_page(netmem)); > + __ClearPageNetpp(page); > + put_page(page); > } > /* An optimization would be to call __free_pages(page, pool->p.order) > * knowing page is not part of page-cache (thus avoiding a > > -- > Pavel Begunkov