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 X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38225C433EF for ; Tue, 7 Sep 2021 03:02:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11A896103E for ; Tue, 7 Sep 2021 03:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229454AbhIGDEC (ORCPT ); Mon, 6 Sep 2021 23:04:02 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:57915 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229797AbhIGDEC (ORCPT ); Mon, 6 Sep 2021 23:04:02 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R351e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UnY7Q0G_1630983774; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UnY7Q0G_1630983774) by smtp.aliyun-inc.com(127.0.0.1); Tue, 07 Sep 2021 11:02:55 +0800 Subject: Re: [PATCH] io_uring: fix bug of wrong BUILD_BUG_ON check To: Pavel Begunkov , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210906151208.206851-1-haoxu@linux.alibaba.com> <702b94b7-bd2f-f89c-b835-3345b8fcaa4a@linux.alibaba.com> From: Hao Xu Message-ID: <5a6a6277-a69d-ad50-a7c5-f3474d1a38c8@linux.alibaba.com> Date: Tue, 7 Sep 2021 11:02:54 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 在 2021/9/7 上午3:15, Pavel Begunkov 写道: > On 9/6/21 6:03 PM, Hao Xu wrote: >> 在 2021/9/6 下午11:22, Pavel Begunkov 写道: >>> On 9/6/21 4:12 PM, Hao Xu wrote: >>>> Some check should be large than not equal or large than. >>>> >>>> Signed-off-by: Hao Xu >>>> --- >>>>   fs/io_uring.c | 6 +++--- >>>>   1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>>> index 2bde732a1183..3a833037af43 100644 >>>> --- a/fs/io_uring.c >>>> +++ b/fs/io_uring.c >>>> @@ -10637,13 +10637,13 @@ static int __init io_uring_init(void) >>>>                sizeof(struct io_uring_rsrc_update2)); >>>>         /* ->buf_index is u16 */ >>>> -    BUILD_BUG_ON(IORING_MAX_REG_BUFFERS >= (1u << 16)); >>>> +    BUILD_BUG_ON(IORING_MAX_REG_BUFFERS > (1u << 16)); >>>>         /* should fit into one byte */ >>>> -    BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8)); >>>> +    BUILD_BUG_ON(SQE_VALID_FLAGS > (1 << 8)); >>> >>> 0xff = 255 is the largest number fitting in u8, >>> 1<<8 = 256. >>> >>> let SQE_VALID_FLAGS = 256, >>> (256 > (1<<8)) == (256 > 256) == false,  even though it can't >>> be represented by u8. >> Isn't SQE_VALID_FLAGS = 256 a valid value for it? > > SQE_VALID_FLAGS is a "bitwise OR" combination of valid flags, so > can't be go beyond 0xff I see, don't know why I mix it with __REQ_F_LAST_BIT in my mind.. > >>> >>> >>>>       BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST); >>>> -    BUILD_BUG_ON(__REQ_F_LAST_BIT >= 8 * sizeof(int)); >>>> +    BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof(int)); >>>>         req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC | >>>>                   SLAB_ACCOUNT); >>>> >>> >> >