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 BC408C636D4 for ; Tue, 14 Feb 2023 01:26:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3AFE66B0073; Mon, 13 Feb 2023 20:26:11 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3602E280002; Mon, 13 Feb 2023 20:26:11 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22749280001; Mon, 13 Feb 2023 20:26:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 1090A6B0073 for ; Mon, 13 Feb 2023 20:26:11 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id D440914016F for ; Tue, 14 Feb 2023 01:26:10 +0000 (UTC) X-FDA: 80464156500.10.324A4B5 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) by imf12.hostedemail.com (Postfix) with ESMTP id 404804000D for ; Tue, 14 Feb 2023 01:26:07 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.111 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676337969; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mkbOLgDW386+TZpdCeDQ1SoHFs4xrL7scuXr1F9lbrA=; b=qmjG9tj27ZllFjZDrMAgVYF8XFOsJQTyAI5yiSdUaYNt4K49DaH55Q234nbd9svs2gBr6n clEVW7JInoQoFkSdEnjCxCnR4/QRPa0/ljrNWHH1U2768J0wv6hck5Td2QsmFwUvW01bG3 eI/77nilsFhMmJfhOijfe1BKrU+Kw4s= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.111 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676337969; a=rsa-sha256; cv=none; b=X4O8TcBsd+T4GYTjeaEpqrrPIfXPgENOnnVELY/ZAwijt8VZt0z82JmbNCM4Ltyx8Y0Act Djk5xvzGSvSu3dG4KYskVXLCsg0Kzi9EL8Vee06AACyYedu+sQIlP61GQOJBVEpBzJ4hBz 5Q96sl7tv6eBFLN4wmDq/WfkOmkSlPo= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R911e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0VbdH-ho_1676337963; Received: from 30.97.48.79(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VbdH-ho_1676337963) by smtp.aliyun-inc.com; Tue, 14 Feb 2023 09:26:03 +0800 Message-ID: Date: Tue, 14 Feb 2023 09:26:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.7.2 Subject: Re: [GIT PULL] hotfixes for 6.2 To: Linus Torvalds , Andrew Morton Cc: linux-mm@kvack.org, mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org References: <20230213140812.db63c7146ebc396691594b73@linux-foundation.org> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 84f1mbasnjyxsx7ue18tkozcreffmhhb X-Rspam-User: X-Rspamd-Queue-Id: 404804000D X-Rspamd-Server: rspam06 X-HE-Tag: 1676337967-319367 X-HE-Meta: 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 dKlJ1vl1 v0jFJfROlRaxkTbtVLDtZi3mOfz/U4phFqUwsVUCsRoFkyhdjgjc8hb5QK/MPqWMLWp0Kv63Bw44lvuMe/hHiTjcR948nF3SsJcGTM88EfvQvqK7eDeX68CSbbjOMU2Q5+cIgaFOQfzmoxlFPl7f71VVZIRV3+aCrJxqS 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: On 2/14/2023 6:19 AM, Linus Torvalds wrote: > On Mon, Feb 13, 2023 at 2:08 PM Andrew Morton wrote: >> >> Kuan-Ying Lee (1): >> mm/gup: add folio to list when folio_isolate_lru() succeed > > Ugh. I really hate fixes like this. > > The problem came from mis-understanding the return value of > folio_isolate_lru(), and thinking that it was a boolean > success/failure thing. > > It wasn't, it was an integer "success/errno" thing, and the sense of > the test was wrong. So the patch is > > - if (!folio_isolate_lru(folio)) > + if (folio_isolate_lru(folio)) > continue; > > but at no point was the code *clarified*. > > Wouldn't it have been much better to write the new code to be > > if (folio_isolate_lru(folio) < 0) > continue; > > to actually make it clear that this is a "negative error return check". > > I've pulled this, but I really think that when somebody notices that > we had a silly bug because of a misunderstanding like this, it's not > just that the bug should be fixed, the code should also be *clarified* > at the same time. Yes, agree, I need to check the return value of folio_isolate_lru() every time when looking at the code. I can help to create a patch to make it clear for all users.