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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DC52EB64D9 for ; Mon, 10 Jul 2023 05:03:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230358AbjGJFDG (ORCPT ); Mon, 10 Jul 2023 01:03:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54110 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230107AbjGJFDF (ORCPT ); Mon, 10 Jul 2023 01:03:05 -0400 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BAE0D120 for ; Sun, 9 Jul 2023 22:03:02 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Vmy4O50_1688965378; Received: from 30.97.48.247(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0Vmy4O50_1688965378) by smtp.aliyun-inc.com; Mon, 10 Jul 2023 13:02:59 +0800 Message-ID: <1a107593-e411-70a0-b6b8-3c34a9036ff3@linux.alibaba.com> Date: Mon, 10 Jul 2023 13:02:58 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH] erofs: fix two loop issues when read page beyond EOF To: Chunhai Guo , "xiang@kernel.org" , "chao@kernel.org" Cc: "huyue2@coolpad.com" , "jefflexu@linux.alibaba.com" , "linux-erofs@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" References: <20230708062432.67344-1-guochunhai@vivo.com> <97875049-8df9-e041-61ca-d90723ba6e82@linux.alibaba.com> From: Gao Xiang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/7/10 12:35, Chunhai Guo wrote: > > > On 2023/7/10 11:37, Gao Xiang wrote: >> >> >> On 2023/7/10 11:32, Chunhai Guo wrote: >>> Hi Xiang, >>> >>> On 2023/7/8 17:00, Gao Xiang wrote: >>>> Hi Chunhai, >>>> >>>> On 2023/7/8 14:24, Chunhai Guo wrote: >>>>> When z_erofs_read_folio() reads a page with an offset far beyond EOF, two >>>>> issues may occur: >>>>> - z_erofs_pcluster_readmore() may take a long time to loop when the offset >>>>>      is big enough, which is unnecessary. >>>>>        - For example, it will loop 4691368 times and take about 27 seconds >>>>>          with following case. >>>>>            - offset = 19217289215 >>>>>            - inode_size = 1442672 >>>>> - z_erofs_do_read_page() may loop infinitely due to the inappropriate >>>>>      truncation in the below statement. Since the offset is 64 bits and >>>>> min_t() truncates the result to 32 bits. The solution is to replace >>>>> unsigned int with another 64-bit type, such as erofs_off_t. >>>>>        cur = end - min_t(unsigned int, offset + end - map->m_la, end); >>>>>        - For example: >>>>>            - offset = 0x400160000 >>>>>            - end = 0x370 >>>>>            - map->m_la = 0x160370 >>>>>            - offset + end - map->m_la = 0x400000000 >>>>>            - offset + end - map->m_la = 0x00000000 (truncated as unsigned int) >>>> >>>> Thanks for the catch! >>>> >>>> Could you split these two into two patches? >>>> >>>> how about using: >>>> cur = end - min_t(erofs_off_t, offend + end - map->m_la, end) >>>> for this? >>>> >>>> since cur and end are all [0, PAGE_SIZE - 1] for now, and >>>> folio_size() later. >>> >>> OK. I will split the patch. >>> >>> Sorry that I can not understand what is 'offend' refer to and what do you mean. Could you please describe it more clearly? >> >> Sorry, there is a typo here, I meant 'offset'. >> >> `cur` and `end` both are not exceed 4096 if your page_size >> is 4096. >> >> Does >> cur = end - min_t(erofs_off_t, offset + end - map->m_la, end) >> >> fix your issue? > > Yes. I think this will fix this issue. Do you mean the below change is unncessary? > >>>> -    unsigned int cur, end, spiltted; > >>>> +    erofs_off_t cur, end; > >>>> +    unsigned int spiltted; Yes, please help send a fix for this! Thanks, Gao Xiang