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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E6A34C55164 for ; Thu, 30 Jul 2026 16:28:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BD2FC6B0088; Thu, 30 Jul 2026 12:27:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B84116B008A; Thu, 30 Jul 2026 12:27:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A993B6B008C; Thu, 30 Jul 2026 12:27:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 820F46B0088 for ; Thu, 30 Jul 2026 12:27:59 -0400 (EDT) Received: from smtpin02.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id E62C0801D0 for ; Thu, 30 Jul 2026 16:27:58 +0000 (UTC) X-FDA: 85045974636.02.4E6B7D8 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf17.hostedemail.com (Postfix) with ESMTP id 2B09C40010 for ; Thu, 30 Jul 2026 16:27:57 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j6tIEUUl; spf=pass (imf17.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@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=1785428877; 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=rK+BoueAu5/AxZSmCB7m3UnuQz/v/hyJVuvyvwdfzbI=; b=Gy8z7flHwrFrhHsBbMBQKlTK9FXZg86pq6gLaDZBNf9v5F7G14RxPvwtVMvHCX7vAIOaP1 md6Wp+2ZeLern5GV527Y0UEcvZZMw4qeCE1bHpLE19sqHGYmKceEHe9nVc2JJ1KqtF6CfC SbXNpqv2L54l6AnH9F+93fTnIp4Py0Y= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785428877; b=uLqVmyTiKDI82ofXzQ/saqUq6nFdN5Xegk+Bzo8I+7ZAmEJ1mz2pb4MRoKunTxeSeLJzgK Bc/r9m7OJ2lSAsExkC4ViwLBFbKdctA1TQsw3ixxQbMjJfCrfM38rS7kKENr9v+vZjDTdQ xoxGGa6ljF+a2A48ilhJ0b8SWepQhzA= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=j6tIEUUl; spf=pass (imf17.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 26CE841448; Thu, 30 Jul 2026 16:27:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0039A1F000E9; Thu, 30 Jul 2026 16:27:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785428876; bh=rK+BoueAu5/AxZSmCB7m3UnuQz/v/hyJVuvyvwdfzbI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=j6tIEUUl1k2gnutXZkMGxBNd7fNFdFSvgUrQ8DMy4QKawOTN7aY89OmbT4lxNCmd3 1esRWbvsURW6XwxQUayLzLSUYh4NwrEi/akNm/+fI5bK9hs5svCoqnZYCDA5zXBh6C fBdz3uiEKzmW6FJn+g5N/pUMp2cbJdK7qV1FdKtKffDOnnP5yzw4Igrcyrvx0HOfxq jurBquJ1T842oQC2dq0m2qBMh1QAmoe7GGoL0aK5f0gZ6fMuaeH6XLXbgSZgr11zmT zEn6d8iQb9INepnOZe8cYbHbQSKgf+aGQINAH7S1FMo/nTeKRELOR2ZC1hQYiC+hve Ymv8eOKjn0YiA== Date: Thu, 30 Jul 2026 17:27:37 +0100 From: "Lorenzo Stoakes (ARM)" To: Andrew Morton Cc: Avi Weiss , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Soheil Hassas Yeganeh , Arjun Roy , Eric Dumazet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: return -ENOMEM for page-table allocation failure in insert_pages() Message-ID: References: <20260730071323.964321-1-thnkslprpt@gmail.com> <20260730091558.12e3d9029002c87c1f00b4aa@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260730091558.12e3d9029002c87c1f00b4aa@linux-foundation.org> X-Rspamd-Queue-Id: 2B09C40010 X-Stat-Signature: w6s581ugqfdb7mbjtyksuoqmuh8spfdu X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1785428877-959710 X-HE-Meta: U2FsdGVkX1/tNH/7rL+si/KaWkuNoe1JMuhvE77WtraWPaskFKGbwG1ELgiD8qAohImwtgXsWjaNKYdmmFymHwiBBoBnrJSlAPdU2bsaidzgTMmmPWi4h7TkM9d6KzIxt+AJmH6L1028/6uJ2xrQhGEos+XMNjggyNNcREIH/Fgcztdh7nsrRYJR/ZnTnsEn1d+wZ3GRDU1RFNx59pCUy+0qF3e/QM5mFRSFINA8q7AbXO3FLEgW2vc5fXIPqR6OCWOyZEle0w9NYjBH3GAjIOSViUyMxvn3rEDcMS3xfht6NudLa3phYU0t0Su6yrCRFTtVhwIryN4u4OHTAzCJ2kcv1wgkiwqB7f7P01F3a7ruoQ5rEQegM145CAipxmYQlf+hUOB/yihv1JzjVR96jXr4ICxqhfrSgHIaWQHwxjATkdjU7Lbx7+HsVi4eAKy0oqGZj3ckQYY3SL7mmiCh7FyRT1E0vXJ6V+ZgNeo72AGNC3GgepSkLSh3PCbORWo6yt9FhLWvNGwKX4qRAu2WDNtiDm6hplG+njws+Add2lCcEKQ9LZhCXzrPSJQmzl+UV4O71DfU+T3fkQ/JVsc0fKBOrJsIEusKBbEgxqfdQkJWi+vHgOgVt9o2j5quysedi9I8iDIQFckaayCCMk6zwtKnuYD9eNAfv9S6TqHssp280+vSIdU3dJ/wGBNShs/VCQH0GWu60y1UwjVJgw8CIaTRBPMC5TdeP+R8Vn6JLrCskOxrdx7a5lfSxxsBg9JCLIxZYq1KVzRSg82/xIjqaGJJ8MfHOvxqS5Qm67+sv7HKQegEufUYzvBElGJqTYcIiiUCXers4ASjO+ytrDsnC2DwU7kgNtJkvjkEawvh4VFUonaqSZc4HNppwvNl6i2sDFt7Xrk1+TVTi/dOJka/DKwrd/idjzf/YcSW5NIXfO0xcXc7T3A49IiMbRVDCdzGwfF+PG94dqVY3peghIR YOv1+M6C oIsy0sZr1k1VOqrIT3pRNzmMtfcUYkydOtO/cqL1jSKRk0vj/sngbNXG2hiP7j9mpu74gkj49AR2TxPMgnm45Y8tvg3U2zQ2uBPHu5wCL9Ab4SXOQie4GsG0Ud1AqFZxSZBMJisAKMK6dlaYFJMTOH3CShkUlVZ110x5iPD12BIlePkt147fumQE3lCdazEy82O/uKBb7EI/YISwtXJQesABdKT6xyrvO44gF4gr9ATnMhw6Ob5pDbFaa7feN+MlTsmsfhp44DohLoHgXhz+37dl2NGrtrJUQU+mvzljfzQD546mdMEbUtV3aDQbeF2W1iLTP Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 30, 2026 at 09:15:58AM -0700, Andrew Morton wrote: > On Thu, 30 Jul 2026 08:42:49 +0100 "Lorenzo Stoakes (ARM)" wrote: > > > pages_to_write_in_pmd = min_t(unsigned long, > > remaining_pages_total, PTRS_PER_PTE - pte_index(addr)); > > > > /* Allocate the PTE if necessary; takes PMD lock once only. */ > > ret = -ENOMEM; <------------------------------ set it again? > > if (pte_alloc(mm, pmd)) > > goto out; > > > > The way this function is written is horrible in general, I hate 'preset default > > return value' as a pattern. > > It used to be the preferred way because > > ret = -ENOMEM; > if (expr) > goto out; > > generated slightly better code than > > if (expr) { > ret = -ENOMEM; > goto out; > } > > Whether that is the case with current compilers I don't know. Thanks for the background on that! I'd put money on there being no difference now :) but in any case that kind of micro-optimisation isn't really a concern here even if it was the case. -- Cheers, Lorenzo