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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Qi Zheng , Lance Yang , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, muchun.song@linux.dev Subject: Re: [PATCH v4 0/6] mm: Unify device DAX and HugeTLB vmemmap population paths Message-Id: <20261010134222.b6fdcb20d8fec5aaceab66ec@linux-foundation.org> In-Reply-To: <20261010075755.83339-1-songmuchun@bytedance.com> References: <20261010075755.83339-1-songmuchun@bytedance.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 99745C0004 X-Rspam-User: X-Stat-Signature: 8wx81rfzxg7qameeoepjbrmhrc3k9umr X-HE-Tag: 1791664944-609422 X-HE-Meta: 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 KYg88DU2 PAAty/3WnTcucAvZeepvXfNIF594E1ZYfn9IHgnkXKgHky6/yro63YaWqlwdCwD8Q5njF6Ih+lcQzbeqQnls82gO5pdXB8pmnvFVtf9b6cqs9BqwZecmQxSwCDtoixYvGOixxehVrY7g2Nm7m8pLF/YVCWnYSMOmYPHKrHHHWJY9ReWwEr1drU+tQa+jU47Nypo8R5Ed66hb5MAkhCeq1F6bVUYthgSwVHxGaMcmQD4UmtwGP/DkxxSmttQTSqUODMyI6Gu1dZNl8WN/04gjbr4/qI1jnNZ8WiLF8cmsJyJVn5suDebL2JHjO6+7KihEEYcLxbLptDZzKo5ieZUQ5EH3OtoGlbRW9lDtx Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 10 Oct 2026 15:57:49 +0800 Muchun Song wrote: > This v4 is based on mm-new commit d5207c6d152c, which contains v6 of > "mm: Switch device DAX to section-based vmemmap optimization" [1]. > > This series is split out from the earlier, larger series "mm: Generalize > HVO for HugeTLB and device DAX" [2]. While the parent series generalizes > vmemmap optimization across HugeTLB and device DAX, this subset addresses > a single, self-contained step: unifying their vmemmap population paths. > > After the preceding Device DAX conversion, both HugeTLB and Device DAX > describe optimized vmemmap mappings through memory-section metadata and > use per-zone shared tail vmemmap pages. The generic code, however, still > carries a Device DAX-specific population flag and compound-page population > path, along with arguments and helpers needed only by that path. > > This series first removes VMEMMAP_POPULATE_DAX and moves selection and > reference handling for the shared tail page into the common vmemmap > population path. It then removes the generic Device DAX-specific > compound-page population path and routes section vmemmap population > through vmemmap_populate(). The powerpc radix path continues to use its > architecture-specific compound-page population implementation for > optimizable sections. > > The remaining patches remove the unused ptpfn argument, open-code > vmemmap_populate_address() now that no caller needs its returned PTE, and > add a warning for inconsistent zone initialization of shared tail vmemmap > pages. > > This is the fourth smaller step toward the broader HVO generalization. > After this series, HugeTLB and Device DAX use the same population model > instead of parallel generic paths, while powerpc keeps its > architecture-specific implementation. Thanks, I've updated mm-unstable to this version, including the -fix. > v4: > - Rebase onto mm-new commit d5207c6d152c, which contains v6 of the Device > DAX section-based vmemmap series. > - Factor the zone mismatch check into a local helper as suggested by Mike > Rapoport. > - Collect Reviewed-by tags from Lance Yang. Here's how v4 altered mm.git: mm/mm_init.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) --- a/mm/mm_init.c~b +++ a/mm/mm_init.c @@ -593,6 +593,15 @@ out: node_states[N_MEMORY] = saved_node_state; } +static inline void vmemmap_optimization_verify_zone(struct page *page) +{ + const unsigned int order = pfn_to_section_compound_order(page_to_pfn(page)); + + VM_WARN_ON_ONCE(vmemmap_optimizable_order(order) && + page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) != + page_zone_id(page)); +} + void __meminit __init_single_page(struct page *page, unsigned long pfn, unsigned long zone, int nid) { @@ -609,9 +618,11 @@ void __meminit __init_single_page(struct if (!is_highmem_idx(zone)) set_page_address(page, __va(pfn << PAGE_SHIFT)); #endif - VM_WARN_ON_ONCE(vmemmap_optimizable_order(pfn_to_section_compound_order(pfn)) && - page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) != - page_zone_id(page)); + /* + * Shared tail struct pages are initialized during vmemmap population, + * before retained struct pages reach here. + */ + vmemmap_optimization_verify_zone(page); } #ifdef CONFIG_NUMA _