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 6FF4DC433EF for ; Mon, 16 May 2022 01:50:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239182AbiEPBug (ORCPT ); Sun, 15 May 2022 21:50:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239155AbiEPBub (ORCPT ); Sun, 15 May 2022 21:50:31 -0400 Received: from zg8tmty1ljiyny4xntqumjca.icoremail.net (zg8tmty1ljiyny4xntqumjca.icoremail.net [165.227.154.27]) by lindbergh.monkeyblade.net (Postfix) with SMTP id DEDF238A1; Sun, 15 May 2022 18:50:25 -0700 (PDT) Received: from [10.8.148.37] (unknown [59.61.78.232]) by app2 (Coremail) with SMTP id SyJltACXhcTfrYFiH34AAA--.113S2; Mon, 16 May 2022 09:50:23 +0800 (CST) Message-ID: <0010ee74-0aac-e998-c74b-84bf7de23335@wangsu.com> Date: Mon, 16 May 2022 09:50:22 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH] bcache: fix wrong BITMASK offset value for BDEV_CACHE_MODE Content-Language: en-US To: Coly Li Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org References: <20210720103246.112027-1-linf@wangsu.com> From: Lin Feng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CM-TRANSID: SyJltACXhcTfrYFiH34AAA--.113S2 X-Coremail-Antispam: 1UD129KBjvJXoW7urW8Ww13Zr15Cw4rtrWUArb_yoW8CFyfpa s5JF4rJF48Xa4I9w1xAF4agrsYv3yrJas3Z34UWF15ury3tw1Fqryruw4Yyr95C3yvkr4I yF1DK345GFW8uFJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkSb7Iv0xC_Kw4lb4IE77IF4wAFc2x0x2IEx4CE42xK8VAvwI8I cIk0rVWrJVCq3wA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK021l84ACjcxK6xIIjx v20xvE14v26w1j6s0DM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4UJVW0owA2z4x0Y4vE x4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS0I0E0xvYzx vE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VCjz48v1sIEY20_Gr4l Yx0Ec7CjxVAajcxG14v26F4UJVW0owAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr4 1lc7I2V7IY0VAS07AlzVAYIcxG8wCY02Avz4vE14v_KwCF04k20xvY0x0EwIxGrwCF04k2 0xvE74AGY7Cv6cx26r48MxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr 0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUAVWUtwCIc40Y0x0E wIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJV W8JwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAI cVC2z280aVCY1x0267AKxVWUJVW8JbIYCTnIWIevJa73UjIFyTuYvjxUTs2-UUUUU X-CM-SenderInfo: holqwq5zdqw23xof0z/ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/13/22 23:20, Coly Li wrote: > On 7/20/21 6:32 PM, Lin Feng wrote: >> Original codes: >> BITMASK(CACHE_SYNC, struct cache_sb, flags, 0, 1); >> BITMASK(CACHE_DISCARD, struct cache_sb, flags, 1, 1); >> BITMASK(CACHE_REPLACEMENT, struct cache_sb, flags, 2, 3); >> ... >> BITMASK(BDEV_CACHE_MODE, struct cache_sb, flags, 0, 4); >> >> Should BDEV_CACHE_MODE bits start from bit-nr 5(2+3) else it overlaps >> with previous defined bit chunks, since we have 4 types of cache modes, >> BDEV_CACHE_MODE will overwrite CACHE_SYNC and CACHE_DISCARD bits. > > The overlap won't happen, previous lines are for cache device, and what > you modified is for backing device. > > And your patch changes the on-disk format, which is unacceptable anyway. > Yes, you are right, this patch happened as I started reading bcache codes, I did not get a whole picture of bcache at that time, I'm sorry for making noise. Thank you, Coly! linfeng > > Coly Li > >> >> This bug stays there since first upstream version of bcache, don't know >> why it lives so long, or am i missing something, please point me out >> if I'm wrong, thanks! >> >> Signed-off-by: Lin Feng >> --- >> include/uapi/linux/bcache.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h >> index cf7399f03b71..dccd89756451 100644 >> --- a/include/uapi/linux/bcache.h >> +++ b/include/uapi/linux/bcache.h >> @@ -288,7 +288,7 @@ BITMASK(CACHE_REPLACEMENT, struct cache_sb, flags, 2, 3); >> #define CACHE_REPLACEMENT_FIFO 1U >> #define CACHE_REPLACEMENT_RANDOM 2U >> >> -BITMASK(BDEV_CACHE_MODE, struct cache_sb, flags, 0, 4); >> +BITMASK(BDEV_CACHE_MODE, struct cache_sb, flags, 5, 4); >> #define CACHE_MODE_WRITETHROUGH 0U >> #define CACHE_MODE_WRITEBACK 1U >> #define CACHE_MODE_WRITEAROUND 2U >