From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 936F8C021B2 for ; Tue, 25 Feb 2025 22:18:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C29C6B008A; Tue, 25 Feb 2025 17:18:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2730E280001; Tue, 25 Feb 2025 17:18:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 13A9A6B0093; Tue, 25 Feb 2025 17:18:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id EB3F86B008A for ; Tue, 25 Feb 2025 17:18:26 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 703CC4925C for ; Tue, 25 Feb 2025 22:18:26 +0000 (UTC) X-FDA: 83159881812.19.E6522F4 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf17.hostedemail.com (Postfix) with ESMTP id AC21640019 for ; Tue, 25 Feb 2025 22:18:24 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gCbcoe1F; spf=pass (imf17.hostedemail.com: domain of will@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=will@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740521904; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=zc7ajnGXiA3almaxHMo8OLZGvnOOFig+wycZzMIPAvc=; b=bVqSEaJfn+iLomh0ZWhFkdBoAEBzE2HXdLfPImjC36gT0scKDsB/PHqlfsvOmHPlpakS27 w2wjJB2J83J63tsfi8vHT0XPAH7cTzB/Qb4OhXKz+fE/w3ujRcXVmMUQ5j6tOwwjqbx8tc 7C7UkdiEA7ZhgEHbMVD3FmJPeBatJ+I= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740521904; a=rsa-sha256; cv=none; b=kC//VW9yR4Lb766bwGKl1X44wRtJdq9C3NOTZFS1+4BtioTJsKw6CZlqeBJFzvaqbd+1Y9 /d/tALXiHDi9OAJ6VbynK2bhUkV7dK8qOnBmqDJqYSXEHtyX5+sGlFEokvAVFo6Hxvx8ZZ TdjWsNSwhILs4kAE+jAjKBn8cI3fEKQ= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=gCbcoe1F; spf=pass (imf17.hostedemail.com: domain of will@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=will@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id A4C765C58C9; Tue, 25 Feb 2025 22:17:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C835EC4CEDD; Tue, 25 Feb 2025 22:18:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740521903; bh=viw/irv5FYM22IZHK1n8uTxMVClyAZnRSx0477w/Koc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gCbcoe1FnWAkKkuivz0Ld9lqqBS4AgOIa9ysfvtOoCndfjUBbAIznfzW4O+zRQ53X 7i9jwLmsvP3bPXO3GhN01JEwreGc+tMywVAe75sYEs9e2EedPocFDz+peOGPBXXnbV TdRuf1qo+Q4tdG4WGlSOOSVn10dyWdYDMPWIizqrIgob/NFWIzpmadvVZ0DhRK+3z2 46QE4El0fvJpbEAohIyW2HetDWLTxPTgirKpKIya72I5N3cHvHQ/tzKaGqT+H5eR+a slzjYb3AlhpaPXDiqa+UzwCCbelVHxPePg0al6q6kQCAheTaao/TjccKU36K2E0FB7 iu9j+Fj87Pe4w== Date: Tue, 25 Feb 2025 22:18:13 +0000 From: Will Deacon To: Ryan Roberts Cc: Catalin Marinas , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Gerald Schaefer , "David S. Miller" , Andreas Larsson , Arnd Bergmann , Muchun Song , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Dev Jain , Kevin Brodsky , Alexandre Ghiti , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 2/4] arm64: hugetlb: Fix huge_ptep_get_and_clear() for non-present ptes Message-ID: <20250225221812.GA23870@willie-the-truck> References: <20250217140419.1702389-1-ryan.roberts@arm.com> <20250217140419.1702389-3-ryan.roberts@arm.com> <20250221153156.GC20567@willie-the-truck> <6ebf36f2-2e55-49b2-8764-90fd972d6e66@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6ebf36f2-2e55-49b2-8764-90fd972d6e66@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspam-User: X-Rspamd-Queue-Id: AC21640019 X-Rspamd-Server: rspam07 X-Stat-Signature: 35ca33nmpr7bxa3sqzmtbjak6c6n39wp X-HE-Tag: 1740521904-680385 X-HE-Meta: U2FsdGVkX1/QIrDxww8ZG5iCJc8GmnSw0owaC1gapExhjPdRzBDrHmzSFdI8iZC3drxsplkrWaTmGEmSXA9MgdlLlCZM+3QxP0kWl3AW3ZfURv39bfWyq+Tmfkf/ihpeeVkQPE3vJS9UE8t8h1bRlM2fMEJJSMBRQuBLd0E8cRNVJ2mYlKN+ZjJftVAGygXYUmKXg2y3GOoTslLllG9EnGIGfFUKtacfo0cDM4cHgty7Eg4xfj9Eba9Hdee/JPIUN0DMz8+Vcfac64bLWcUiLXwKa8zd3YUlaxhm2N8pCWz6pinsXJi3v8cpouMDYD7Fcw2fsUp7s/TCRPqRMFMDvPKvPiLVqDW9ZL8IUSuGSZe1pzQGe+cLFAHz8MnSz6MggUkdUDdfPfQvv+GlWiajX3BsrdcuiRFrkPukZ+nS5n90A04JFdQmQjFHKCvpNimJmopPuSDZ3iy2r1tQbp2V9HrlxLZOsGJMALuTE0f4ZQTpODoyaUGXTPIVwQhRiqlukggXTf4p4KYwZRNKI0gYR6cW2yzH49fKY1sIU5sUS0zq7LslYmwwvEvO8sfXibJeyeuc0bWibKabqTa12WCnj3IzUlPaVthrPt3mPId3FVOW95131T+6agRzXjJ+SY2O8I+mqYayWTV0vbCIe0sz5S2f206JKMss4W9iGLCjQOsL19gTWkecCyW42NXBTWUfeiAtyJXErDNO405RKyAzZJ2kfOWUI6eZnEaRS0SRHW82uVRkfHLb+xcK5tUwJLxhs2oDW1yGqZ3gK6yW/3LoVm6B6UOBFZdiGoNNOhndGbftYH9V23SwnAFcy3ueJOhtkF10O9yUJFp9dqs3rSgzg7l9T3WN1nIbs8oMvkMJdha8Cnt3w/tvCp4WUCNOtp+6U6DCy48oonDLNErMOXuV4C6ZAPfAKWu1q40xm6GShZpgf7umR9GBaodNNrz2Hn0BesFBMGNjI+kPdgxLUDd uW3jE+Il ivtarPnigg8Dr5YaurghQU80ELoKaYyCMobaHottoveC0qMsR1RdobWjd1VbFnuuqTD9W0/g45sFivKquW1kEnRwH2XsSOLgHs7uTvyrqCQ3KDMY6BJtrg0i6WgZ5wYxDw+BmCnChsPa6uL+vZw48m0S7yKndJmxxX+KwKTPrAMI1cppYwsYAaY3fDSukS+YSapL8d1hieXY2KYzI4W1m516H0k2p66EDY9AacMt/zHv5DRNMzXZJqw7nVAhUvoBZRGV/hx1SOf4EHM0= 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 Mon, Feb 24, 2025 at 12:11:19PM +0000, Ryan Roberts wrote: > On 21/02/2025 15:31, Will Deacon wrote: > > On Mon, Feb 17, 2025 at 02:04:15PM +0000, Ryan Roberts wrote: > >> + pte = __ptep_get_and_clear(mm, addr, ptep); > >> + present = pte_present(pte); > >> + while (--ncontig) { > >> + ptep++; > >> + addr += pgsize; > >> + tmp_pte = __ptep_get_and_clear(mm, addr, ptep); > >> + if (present) { > >> + if (pte_dirty(tmp_pte)) > >> + pte = pte_mkdirty(pte); > >> + if (pte_young(tmp_pte)) > >> + pte = pte_mkyoung(pte); > >> + } > >> } > > > > nit: With the loop now structured like this, we really can't handle > > num_contig_ptes() returning 0 if it gets an unknown size. Granted, that > > really shouldn't happen, but perhaps it would be better to add a 'default' > > case with a WARN() to num_contig_ptes() and then add an early return here? > > Looking at other users of num_contig_ptes() it looks like huge_ptep_get() > already assumes at least 1 pte (it calls __ptep_get() before calling > num_contig_ptes()) and set_huge_pte_at() assumes 1 pte for the "present and > non-contig" case. So num_contig_ptes() returning 0 is already not really > consumed consistently. > > How about we change the default num_contig_ptes() return value to 1 and add a > warning if size is invalid: Fine by me! I assume you'll fold that in and send a new version, along with the typo fixes? Cheers, Will