From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A685C3D7D94 for ; Wed, 30 Sep 2026 19:02:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794924; cv=none; b=VIxtiyci54aafuD0uypkFoBJJpMetfu5jupjFAVxxbpFVoGz+m/sGc0ETX4DYGO3MuNigkThN6ufOpvU5DszYbjOFsvDy9tvhG4sdKU9UD7o8+Al2mrss/G3+koV0Kh3o90gRs0KseetoMHmBS7atHymMfyf6KV3JFRBuhD5ntY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794924; c=relaxed/simple; bh=xvGN7WU5nc+uhn6HQF4jIjTZ+kVdxOXPkeBEvYuCreY=; h=Date:To:From:Subject:Message-Id; b=nbDrvw+VAhAomiTvRjozOtcxPFSCfDVOpf+W1mhgZGpex5lkTWStPo2KkEhYqu33eAMKQOlQf9a+MN5VHPzKe+MojfSGfpRA89tZdIsFJu7FjKiPuiuFhkKGphQFm/xFnfzg8rrWSoC92Ftf4034KPr9l7NzlVN4W3que6xuYdg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=y8TVGqZT; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="y8TVGqZT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8297E1F000FF; Wed, 30 Sep 2026 19:02:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1790794922; bh=YtOjC4+4Lw3EzxBO5+uqI8gy5S+IS/dqOln2K1qzzFk=; h=Date:To:From:Subject; b=y8TVGqZT5B3MHJcvqFmr3zEgl8hNzoq5jQ4BhSx9pEdKoqb1DDKPOhSF7anfehiyk QIL+8UEOE8awxK04jUAIUKLYRYozgnFWOaHfqlEvhSTz/dYlX1aTCeObn6+jbokLRA 6zShWAW4QhTnuQwlRl60wIFz2DTZw6N+o319yRE8= Date: Wed, 30 Sep 2026 12:02:02 -0700 To: mm-commits@vger.kernel.org,muchun.song@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: + powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch added to mm-unstable branch Message-Id: <20260930190202.8297E1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: powerpc/mm: switch device DAX to shared tail vmemmap pages has been added to the -mm mm-unstable branch. Its filename is powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Muchun Song Subject: powerpc/mm: switch device DAX to shared tail vmemmap pages Date: Wed, 30 Sep 2026 22:06:24 +0800 The powerpc radix compound vmemmap population path still finds a reusable tail page by walking the vmemmap page tables. Switch it to the common vmemmap_shared_tail_page() helper instead, so it can use the shared vmemmap page directly to simplify the code. This removes the powerpc-specific tail-page lookup and its fallback path and aligns the device DAX vmemmap optimization path with HugeTLB. Link: https://lore.kernel.org/20260930140627.57431-10-songmuchun@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Cc: Oscar Salvador Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Jonathan Corbet Cc: Lorenzo Stoakes Cc: Mike Rapoport Cc: Qi Zheng Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Ritesh Harjani (IBM) Cc: Shrikanth Hegde Cc: Randy Dunlap Cc: Lance Yang --- arch/powerpc/mm/book3s64/radix_pgtable.c | 80 ++------------------- include/linux/vmemmap-optimization.h | 6 + mm/sparse-vmemmap.c | 6 - 3 files changed, 15 insertions(+), 77 deletions(-) --- a/arch/powerpc/mm/book3s64/radix_pgtable.c~powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include @@ -1250,59 +1251,6 @@ static pte_t * __meminit radix__vmemmap_ return pte; } -static pte_t * __meminit vmemmap_compound_tail_page(unsigned long addr, - unsigned long pfn_offset, int node) -{ - pgd_t *pgd; - p4d_t *p4d; - pud_t *pud; - pmd_t *pmd; - pte_t *pte; - unsigned long map_addr; - - /* the second vmemmap page which we use for duplication */ - map_addr = addr - pfn_offset * sizeof(struct page) + PAGE_SIZE; - pgd = pgd_offset_k(map_addr); - p4d = p4d_offset(pgd, map_addr); - pud = vmemmap_pud_alloc(p4d, node, map_addr); - if (!pud) - return NULL; - pmd = vmemmap_pmd_alloc(pud, node, map_addr); - if (!pmd) - return NULL; - if (pmd_leaf(*pmd)) - /* - * The second page is mapped as a hugepage due to a nearby request. - * Force our mapping to page size without deduplication - */ - return NULL; - pte = vmemmap_pte_alloc(pmd, node, map_addr); - if (!pte) - return NULL; - /* - * Check if there exist a mapping to the left - */ - if (pte_none(*pte)) { - /* - * Populate the head page vmemmap page. - * It can fall in different pmd, hence - * vmemmap_populate_address() - */ - pte = radix__vmemmap_populate_address(map_addr - PAGE_SIZE, node, NULL, NULL); - if (!pte) - return NULL; - /* - * Populate the tail pages vmemmap page - */ - pte = radix__vmemmap_pte_populate(pmd, map_addr, node, NULL, NULL); - if (!pte) - return NULL; - vmemmap_verify(pte, node, map_addr, map_addr + PAGE_SIZE); - return pte; - } - return pte; -} - int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, unsigned long start, unsigned long end, int node, @@ -1320,6 +1268,12 @@ int __meminit vmemmap_populate_compound_ pud_t *pud; pmd_t *pmd; pte_t *pte; + struct page *tail_page; + unsigned int order = pfn_to_section_compound_order(start_pfn); + + tail_page = vmemmap_shared_tail_page(order, device_zone(node)); + if (!tail_page) + return -ENOMEM; for (addr = start; addr < end; addr = next) { @@ -1349,10 +1303,9 @@ int __meminit vmemmap_populate_compound_ next = addr + PAGE_SIZE; continue; } else { - unsigned long nr_pages = pgmap_vmemmap_nr(pgmap); + unsigned long nr_pages = 1UL << order; unsigned long addr_pfn = page_to_pfn((struct page *)addr); unsigned long pfn_offset = addr_pfn - ALIGN_DOWN(addr_pfn, nr_pages); - pte_t *tail_page_pte; /* * if the address is aligned to huge page size it is the @@ -1377,23 +1330,8 @@ int __meminit vmemmap_populate_compound_ next = addr + 2 * PAGE_SIZE; continue; } - /* - * get the 2nd mapping details - * Also create it if that doesn't exist - */ - tail_page_pte = vmemmap_compound_tail_page(addr, pfn_offset, node); - if (!tail_page_pte) { - - pte = radix__vmemmap_pte_populate(pmd, addr, node, NULL, NULL); - if (!pte) - return -ENOMEM; - vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); - - next = addr + PAGE_SIZE; - continue; - } - pte = radix__vmemmap_pte_populate(pmd, addr, node, NULL, pte_page(*tail_page_pte)); + pte = radix__vmemmap_pte_populate(pmd, addr, node, NULL, tail_page); if (!pte) return -ENOMEM; vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); --- a/include/linux/vmemmap-optimization.h~powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/include/linux/vmemmap-optimization.h @@ -83,6 +83,12 @@ static inline unsigned int pfn_to_sectio { return 0; } + +static inline struct page *vmemmap_shared_tail_page(unsigned int order, + struct zone *zone) +{ + return NULL; +} #endif /* CONFIG_VMEMMAP_OPTIMIZATION */ static inline bool vmemmap_optimizable_pfn(unsigned long pfn) --- a/mm/sparse-vmemmap.c~powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages +++ a/mm/sparse-vmemmap.c @@ -240,12 +240,6 @@ struct page __ref *vmemmap_shared_tail_p return page; } -#else -static inline struct page *vmemmap_shared_tail_page(unsigned int order, - struct zone *zone) -{ - return NULL; -} #endif static __meminit void *vmemmap_alloc_pte(unsigned long pfn, int node, _ Patches currently in -mm which might be from muchun.song@linux.dev are mm-sparse-vmemmap-factor-out-shared-vmemmap-tail-page-allocation.patch mm-sparse-vmemmap-allocate-shared-tail-page-array-dynamically.patch mm-sparse-vmemmap-introduce-config_vmemmap_optimization.patch mm-sparse-vmemmap-open-code-init_compound_tail.patch mm-sparse-vmemmap-prepare-dax-vmemmap-population-for-compound-page-orders.patch mm-sparse-vmemmap-set-compound-page-order-for-device-dax.patch mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages.patch mm-sparse-vmemmap-switch-device-dax-to-shared-tail-vmemmap-pages-fix.patch mm-sparse-vmemmap-move-vmemmap-optimization-helpers-to-a-public-header.patch powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages.patch powerpc-mm-switch-device-dax-to-shared-tail-vmemmap-pages-fix.patch mm-sparse-vmemmap-drop-the-extra-tail-page-from-device-dax-reservation.patch mm-sparse-vmemmap-drop-unused-section_nr_vmemmap_pages-arguments.patch documentation-mm-update-dax-vmemmap-deduplication-docs.patch mm-sparse-vmemmap-drop-vmemmap_populate_dax.patch mm-sparse-vmemmap-support-device-dax-in-common-vmemmap-path.patch mm-sparse-vmemmap-drop-device-dax-specific-population-path.patch mm-sparse-vmemmap-remove-the-unused-ptpfn-argument.patch mm-sparse-vmemmap-open-code-vmemmap_populate_address.patch mm-mm_init-add-zone-mismatch-warning-during-page-init.patch