From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793192689; b=SyJ00Y4ODBnfppY4lDuXBT7FhQHBOthgSwk/B4nbmM1nrW6Q6CGegWQg18L8/QaEzJnU UyWxOSt+p5NB9dS9IO7KSE1btpt6Eh501+tWPrCTg42KKRVr9JqQeWJ0GLxFWvlKDteUW rmeO14eje89y/adt9VZYOCloVsQlukOAWv77HIYtoNQ7LuNQXNt5HoagnY7LXuKVN+e0o IpqJfe0Xk4kyppTwzC9fmhXwbNvkSba1CL3SpJDTRUDZS6KfrpHlc9OiGuzv0InirTbRt OuCAmXwyRlR85+af+ZwtP9X+JquuC0NHk+M0GHJI4KurgGTgyfCZ7rpvkEmJHBBTwhg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793192689; h=Received:DKIM-Signature:Received:Received:X-ME-Sender:X-ME-Received: X-ME-Proxy-Cause:X-ME-Proxy:Feedback-ID:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=OG80Mz0mVm49EyuyKHOkJqtYHLMvKooWxYEt+ri6Okc=; b=s2Xu62MJ2DCCBTOf87qvmrcyR8Zvq9jtCr+aPx1MmO3yMbvhfOPqdVKykf9jmbVa4A6V l1oz0nzvaXDciaoc6CQMnkCCBc4Y/fqxmEPQY5jMrEseM4vV/Wg2xPoDCkShCeJ94mU8T RrUtjVpkw2QIcE74ch4jNdCTQTurpuNeAU3HZdlIr+vaGknLc81b9CMFU50gqU7N5rM8v vi5ERGNt5dj1eVacn5zkNKLQ+gVKcpJyZ70vb3MbQIwzkPFShHe1HTrzHHTbLUTYlL4KK 1kJwkpy5QGOH5O1S9kK+Gu2IGh1csAQDMh0peWaUlSBEvI6XOu8kEXyBuwJC+Q1vtKg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NhoVazCk; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B625606A31C for ; Wed, 28 Oct 2026 13:04:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=NhoVazCk Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1D551F01825; Wed, 28 Oct 2026 13:04:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793192689; bh=OG80Mz0mVm49EyuyKHOkJqtYHLMvKooWxYEt+ri6Okc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=NhoVazCkHOBZd/Zh8WtWlntaIO9ino1lTyefSK8Dzb4X7rZBNS7fhkNVtdGcP7Vdb cGNbg6lFcEZvFjT9yMlCTwP0SqOF9qq5NhXW5cvhPl0xIwEr/6L1LkNZ/uQXf4aKoi clPXr9aGTTc3EyDb+CotvlY11YlESdSO1VdrbdyIfTAyysBgktMbUkrEUpSh9IMlcM ftZdaz6ql75fiVG+RctbuKjhXW5zisfa9P6A7RWIlUDFmg1y4qEYh9gGrGcv24aiMY RQJ+Uor7BCdHWg/Ja0NxSTpMLPcpXq6FVL+09fkmcCDKK41pgGMTScRqAMVA7WiXTd C1UvOifI78Avg== Received: from phl-compute-11.internal (phl-compute-11.internal [10.202.2.51]) by mailfauth.ams.internal (Postfix) with ESMTP id 72805198003A; Wed, 28 Oct 2026 09:04:41 -0400 (EDT) Received: from phl-frontend-04 ([10.202.2.163]) by phl-compute-11.internal (MEProxy); Wed, 28 Oct 2026 09:04:46 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTFg4m4oPEAUf0wKUWw/Iv3SvfDuV2dwoufosxi56rG8rE3yzXkDOL9mHtdMD5t3xb TNtQvdWPVpliQZzMEq2j9Gt/Qeqa/rF77vTyxnTf5UOLPNJ2zUCh17VsnOcEYbxGgk6pd/ jnrFGdaKttqtWNKjNbixKC92UE8SCbRpRx0WxGiIqSl0J0ICk0JQhy9Sr/LMCk3/IVcW/o bCjLH09OVr/VQlaboh+GTF0eV9P0WsRQ0NN8dvTtbJ5CULwJ3YspX58BzjPnKc4esZY0AE vCO/2EXsD9kJV70LTbLoWjGuNnwDImFpXgd/qrFbj8lz7uaYEYKynkoZbbntZlYoJ2cVe9 /+rhqV/xdrC6ND9aiGvuSZn+fk+lMFKBk+CwBAGjoY66y4uTs5oqVkdwtiVpN3jnfufyiw mbFGB54MLhrD1QUgxn90nVffgd8oQRT4PZ2d0Cv8SF1Gpgx6GZU5qUwdlixKbbdcCnstPy C4OiiGs/7AHNy17plPHaquUuUuXG0T7RKsstw38S2VOjByMTyHT12LhV9xiy9nSaBbtkzo eBHrVxgrtsC+JoLewb5t0X58mNTZctuMyI/X+JJS417uckswZSke7odEKVKiXLKSFCGJgN lxiRKVDKgquvVnW9gYMK5Q2ompqZeG5/mSl+cviBwf32c/V8SUzaJThtISOA X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 28 Oct 2026 09:04:39 -0400 (EDT) Date: Wed, 28 Oct 2026 13:04:38 +0000 From: Kiryl Shutsemau To: Muchun Song Cc: "David Hildenbrand (Arm)" , Peter Zijlstra , Andrew Morton , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, Dave Hansen , Andy Lutomirski Subject: Re: [PATCHv7 13/18] mm: Drop fake head checks Message-ID: References: <20261027110028.GH2668564@noisy.programming.kicks-ass.net> <070DDE5C-2183-4A8B-AC2D-891CAE15E581@linux.dev> <4A32F5E6-977D-4720-8723-B19AFBC08FCF@linux.dev> <7cb3dd91-f518-49b6-b311-9ec807b3c63b@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7cb3dd91-f518-49b6-b311-9ec807b3c63b@linux.dev> On Wed, Oct 28, 2026 at 10:38:22AM +0800, Muchun Song wrote: > > Bootmem folios optimized in early boot get their tails mapped writable > > and write protected later. Drop the write protect step. > > For bootmem folios, I don't think the RO mapping should be removed, > because we are in the initialization stage of struct page. > No one should touch those pages at this point; otherwise, they could > encounter uninitialized struct page as well. This assumes no race > exists during early boot. > > Since such a problem does not exist during the boot stage, why should > we give up the protection that RO provides? Agreed. Nothing does a lockless get on bootmem folios before hugetlb takes them, so they can stay RO. I will keep the pre-HVO write-protect and post the patch. -- Kiryl Shutsemau / Kirill A. Shutemov