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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 , 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: Re: [PATCH v1 13/36] mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap() Message-ID: References: <20250827220141.262669-1-david@redhat.com> <20250827220141.262669-14-david@redhat.com> <377449bd-3c06-4a09-8647-e41354e64b30@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <377449bd-3c06-4a09-8647-e41354e64b30@redhat.com> X-Rspamd-Queue-Id: 94C3E180016 X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: utxmqma4d5rdp76rkby9o17xqtynge7f X-HE-Tag: 1756368383-484603 X-HE-Meta: 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 ZOz2ynUk WnNTOik23t7rmXGr4uxgoYJQ5MxQjvWh7hBfnG2cHcFhmL/YzrSaw3P3ADp7Rp6KBfYXA0dP1A9ZSL/j/s+uCwybaDMgMgWRTsjM83TMl3KsS4prRiUjFkKJPrHSgUZiJCIYXnxeejkMEFqEiwsvLo1ZU2FHLz4UTCsFbCqlFGNQ/h8tNoGt6H5sSENrhP7iShDGRQQdAVYZycci+SaDiKbKi2t+ocjQ+pXDOPg6eyFzULeiJayyY3W6j4zGh/kMKw+5nyBMv3QOgsYfTZdnR62MiiXXbSufdRo2xz+ly2uUY1QHyJ03/avKCT0hWKlh61akPQlMFvFkvSsY= 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 Thu, Aug 28, 2025 at 09:44:27AM +0200, David Hildenbrand wrote: > On 28.08.25 09:21, Mike Rapoport wrote: > > On Thu, Aug 28, 2025 at 12:01:17AM +0200, David Hildenbrand wrote: > > > 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. > > > > ^ not? ;-) > > Can you elaborate? Oh, sorry, I misread "uninitialized". Still, I'd phrase it as /* * We marked all tail pages with memblock_reserved_mark_noinit(), * so we must initialize them here. */ > -- > Cheers > > David / dhildenb > -- Sincerely yours, Mike.