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Howlett" , Linus Torvalds , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Subject: [PATCH v1 13/36] mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap() Date: Thu, 28 Aug 2025 00:01:17 +0200 Message-ID: <20250827220141.262669-14-david@redhat.com> In-Reply-To: <20250827220141.262669-1-david@redhat.com> References: <20250827220141.262669-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 019171C000D X-Stat-Signature: 8d76ewpm4kc8p5d81rmkuyburs4mz18a X-Rspam-User: X-HE-Tag: 1756332369-956777 X-HE-Meta: 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 LdhZEDuv OHmVRlcZ2KkLsxjI8UkXfsbJOoWOIn6KQ8zimTSlStT96D688O8avKOJHl9y78pgTS1RwRhq2YOa6r4yboxQliAzHXWksPl2MPV35XTPWqWtZr97KDYRLksCgO/OeAZrfh7+TCXK/I/fcCjftGvi6RP4XtnJSMev3l6s4N6xOiHYtOZ8SY5TgQ4vCCStYZucP0pubPPnoGu4OSGTqci7zwaq+pAWtvTFj5bwkSfCwUI/SIuEqOYa1NFSmQce+K9wx24WpWnEnwb0vSHZeax+OrnUCALYsT70+lHElnMIOaghMvk3whFV5ZnbVFkhE8kGt97w8mlevyWy04afAvrbsBdizZs6x/4HLUe+AqPL+g5iPZAYcObzDblQ4BVvsDnoF2TQH 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: We can now safely iterate over all pages in a folio, so no need for the pfn_to_page(). Also, as we already force the refcount in __init_single_page() to 1, we can just set the refcount to 0 and avoid page_ref_freeze() + VM_BUG_ON. Likely, in the future, we would just want to tell __init_single_page() to which value to initialize the refcount. Further, adjust the comments to highlight that we are dealing with an open-coded prep_compound_page() variant, and add another comment explaining why we really need the __init_single_page() only on the tail pages. Note that the current code was likely problematic, but we never ran into it: prep_compound_tail() would have been called with an offset that might exceed a memory section, and prep_compound_tail() would have simply added that offset to the page pointer -- which would not have done the right thing on sparsemem without vmemmap. Signed-off-by: David Hildenbrand --- mm/hugetlb.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 4a97e4f14c0dc..1f42186a85ea4 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3237,17 +3237,18 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio, { enum zone_type zone = zone_idx(folio_zone(folio)); int nid = folio_nid(folio); + struct page *page = folio_page(folio, start_page_number); unsigned long head_pfn = folio_pfn(folio); unsigned long pfn, end_pfn = head_pfn + end_page_number; - int ret; - - for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) { - struct page *page = pfn_to_page(pfn); + /* + * We mark all tail pages with memblock_reserved_mark_noinit(), + * so these pages are completely uninitialized. + */ + for (pfn = head_pfn + start_page_number; pfn < end_pfn; page++, pfn++) { __init_single_page(page, pfn, zone, nid); prep_compound_tail((struct page *)folio, pfn - head_pfn); - ret = page_ref_freeze(page, 1); - VM_BUG_ON(!ret); + set_page_count(page, 0); } } @@ -3257,12 +3258,15 @@ static void __init hugetlb_folio_init_vmemmap(struct folio *folio, { int ret; - /* Prepare folio head */ + /* + * This is an open-coded prep_compound_page() whereby we avoid + * walking pages twice by initializing/preparing+freezing them in the + * same go. + */ __folio_clear_reserved(folio); __folio_set_head(folio); ret = folio_ref_freeze(folio, 1); VM_BUG_ON(!ret); - /* Initialize the necessary tail struct pages */ hugetlb_folio_init_tail_vmemmap(folio, 1, nr_pages); prep_compound_head((struct page *)folio, huge_page_order(h)); } -- 2.50.1