From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6EA0C849C; Thu, 28 Aug 2025 08:06:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756368382; cv=none; b=S4h74yPY8V7GcIQC6RpRErcXEDvy/jqH4nmgMIYnvOywePTBx5x/hwh7QpPw+1Ib/sPzQkhhWZxE9svEiZojuYlYkDZ70ygDLionbLplstMqiP5y7eZzy846qSVZE/0mXt1PJDI27sPednh2q+knn15AoVCOhGKHOZQf6O//T6o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756368382; c=relaxed/simple; bh=8h3kXegWoTZB71c0/EOwOGHCDp9sWcsK0sA1Fhv8ieM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GRrAcaBm0odbUrLDBArrVz7DPEugEjWrkerztTOugXc/DpXktIba8fyaA+YbdOftFLprObfiHbW3jteleyIqDEtauCUU9v6PzPBD3PipTwP72ZhI8JaiFJ4mDLlimeMWXCY1aMGMnx0hWi66L4Yb+SV+S07oV3DPH8VyO+9c8ss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=vBGjtF+G; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="vBGjtF+G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04174C4CEEB; Thu, 28 Aug 2025 08:06:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756368382; bh=8h3kXegWoTZB71c0/EOwOGHCDp9sWcsK0sA1Fhv8ieM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vBGjtF+Gn0Ojo1KVedpXcUo5UNPKTP/e/wulKW1x/vz4AZ2m1wZ6thc/Lps+xlQF6 DwTPlbi9e+FvV8tPla4md0hJavNfKkFh5xzuaITPDW7oEVPRJuMnRQWVL0KaIZNEg4 4T8RWZ0Rh3tP7DQ1cUFf+tX54SzZArEKNTK8B97r3LwqCLB/OYDUdoSALNtM9+F5Dv KS7BJVC9pXBz7unzWbhSWZxMJ+vW4HayoOqIpbx1GOFj1iYowGmGtL7JMjJ/av8GLW NBVH9qH0fuKVNbHUV4tP2RMgGBJTXgbSoYrIDxxmnUwirlVFE2Z9r3rXRQTzilPCUm zB6/THzmytDdA== Date: Thu, 28 Aug 2025 11:06:07 +0300 From: Mike Rapoport To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. 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> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <377449bd-3c06-4a09-8647-e41354e64b30@redhat.com> 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.