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 34414C46467 for ; Tue, 29 Nov 2022 01:15:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234919AbiK2BPI (ORCPT ); Mon, 28 Nov 2022 20:15:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234609AbiK2BPF (ORCPT ); Mon, 28 Nov 2022 20:15:05 -0500 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 163B721E2F; Mon, 28 Nov 2022 17:15:03 -0800 (PST) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4NLksF1fwYz4f3nTp; Tue, 29 Nov 2022 09:14:57 +0800 (CST) Received: from [10.174.176.73] (unknown [10.174.176.73]) by APP1 (Coremail) with SMTP id cCh0CgDHcK8SXYVjVeUGBQ--.44020S3; Tue, 29 Nov 2022 09:15:00 +0800 (CST) Subject: Re: [PATCH v2] blk-iocost: fix shift-out-of-bounds in iocg_hick_delay() To: Tejun Heo , Li Jinlin Cc: josef@toxicpanda.com, axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, liuzhiqiang26@huawei.com, "yukuai (C)" References: <20221128030413.882998-1-lijinlin3@huawei.com> From: Yu Kuai Message-ID: Date: Tue, 29 Nov 2022 09:14:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: cCh0CgDHcK8SXYVjVeUGBQ--.44020S3 X-Coremail-Antispam: 1UD129KBjvdXoW7Gr18Ww18Jry3urWUtw1xGrg_yoWkAFb_Wr yFga1DCr15tF4fCayDCr43JFZIqF1UXw1xWrZrtayDWr4rJFykCrWUGr17urWxG34jyFWU ArykAw4FgFs8CjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUbzAYFVCjjxCrM7AC8VAFwI0_Gr0_Xr1l1xkIjI8I6I8E6xAIw20E Y4v20xvaj40_Wr0E3s1l1IIY67AEw4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwV A0rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x02 67AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7I2V7IY0VAS07AlzVAYIcxG8wCF04k20xvY0x0E wIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I0E74 80Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0 I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr1lIxAIcVCF04 k26cxKx2IYs7xG6rW3Jr0E3s1lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY 1x0267AKxVWUJVW8JbIYCTnIWIevJa73UjIFyTuYvjxUrR6zUUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, ÔÚ 2022/11/29 3:58, Tejun Heo дµÀ: > On Mon, Nov 28, 2022 at 11:04:13AM +0800, Li Jinlin wrote: >> /* calculate the current delay in effect - 1/2 every second */ >> tdelta = now->now - iocg->delay_at; >> if (iocg->delay) >> - delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC); >> + delay = iocg->delay >> >> + min_t(u64, div64_u64(tdelta, USEC_PER_SEC), 63); > > I replied earlier but the right thing to do here is setting delay to 0 if > the shift is >= 64. Perhaps following change will make more sense? @@ -1322,18 +1323,19 @@ static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now) { struct ioc *ioc = iocg->ioc; struct blkcg_gq *blkg = iocg_to_blkg(iocg); - u64 tdelta, delay, new_delay; + u64 delay = 0; + u64 new_delay; s64 vover, vover_pct; u32 hwa; lockdep_assert_held(&iocg->waitq.lock); /* calculate the current delay in effect - 1/2 every second */ - tdelta = now->now - iocg->delay_at; - if (iocg->delay) + if (iocg->delay && now->now > iocg->delay_at) { + u64 tdelta = now->now - iocg->delay_at; + delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC); - else - delay = 0; + } > > Thanks. >