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=-13.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 8B67DC43461 for ; Mon, 7 Sep 2020 07:40:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 61695207C3 for ; Mon, 7 Sep 2020 07:40:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726833AbgIGHkD (ORCPT ); Mon, 7 Sep 2020 03:40:03 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:38306 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726780AbgIGHkC (ORCPT ); Mon, 7 Sep 2020 03:40:02 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 49C84B6DC479BDDA8B6A; Mon, 7 Sep 2020 15:39:59 +0800 (CST) Received: from [127.0.0.1] (10.174.177.253) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.487.0; Mon, 7 Sep 2020 15:39:54 +0800 Subject: Re: [PATCH 1/1] block: move the PAGE_SECTORS definition into To: Coly Li CC: Jens Axboe , Kent Overstreet , Alasdair Kergon , Mike Snitzer , dm-devel , linux-block , linux-kernel , linux-bcache References: <20200821020345.3358-1-thunder.leizhen@huawei.com> <8aa638b7-6cfd-bf3d-8015-fbe59f28f31f@suse.de> From: "Leizhen (ThunderTown)" Message-ID: Date: Mon, 7 Sep 2020 15:39:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <8aa638b7-6cfd-bf3d-8015-fbe59f28f31f@suse.de> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.253] X-CFilter-Loop: Reflected Sender: linux-bcache-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org Hi, Jens Axboe, Alasdair Kergon, Mike Snitzer: What's your opinion? On 2020/8/21 15:05, Coly Li wrote: > On 2020/8/21 14:48, Leizhen (ThunderTown) wrote: >> >> >> On 8/21/2020 12:11 PM, Coly Li wrote: >>> On 2020/8/21 10:03, Zhen Lei wrote: >>>> There are too many PAGE_SECTORS definitions, and all of them are the >>>> same. It looks a bit of a mess. So why not move it into , >>>> to achieve a basic and unique definition. >>>> >>>> Signed-off-by: Zhen Lei >>> >>> >>> A lazy question about page size > 4KB: currently in bcache code the >>> sector size is assumed to be 512 sectors, if kernel page > 4KB, it is >>> possible that PAGE_SECTORS in bcache will be a number > 8 ? >> >> Sorry, I don't fully understand your question. I known that the sector size >> can be 512 or 4K, and the PAGE_SIZE can be 4K or 64K. So even if sector size >> is 4K, isn't it greater than 8 for 64K pages? >> >> I'm not sure if the question you're asking is the one Matthew Wilcox has >> answered before: >> https://www.spinics.net/lists/raid/msg64345.html > > Thank you for the above information. Currently bcache code assumes > sector size is always 512 bytes, you may see how many "<< 9" or ">> 9" > are used. Therefore I doubt whether current code may stably work on e.g. > 4Kn SSDs (this is only doubt because I don't have such SSD). > > Anyway your patch is fine to me. This change to bcache doesn't make > thins worse or better, maybe it can be helpful to trigger my above > suspicious early if people do have this kind of problem on 4Kn sector SSDs. > > For the bcache part of this patch, you may add, > Acked-by: Coly Li > > Thanks. > > Coly Li > >>>> --- >>>> drivers/block/brd.c | 1 - >>>> drivers/block/null_blk_main.c | 1 - >>>> drivers/md/bcache/util.h | 2 -- >>>> include/linux/blkdev.h | 5 +++-- >>>> include/linux/device-mapper.h | 1 - >>>> 5 files changed, 3 insertions(+), 7 deletions(-) >>>> >>> >>> [snipped] >>> >>>> diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h >>>> index c029f7443190805..55196e0f37c32c6 100644 >>>> --- a/drivers/md/bcache/util.h >>>> +++ b/drivers/md/bcache/util.h >>>> @@ -15,8 +15,6 @@ >>>> >>>> #include "closure.h" >>>> >>>> -#define PAGE_SECTORS (PAGE_SIZE / 512) >>>> - >>>> struct closure; >>>> >>>> #ifdef CONFIG_BCACHE_DEBUG >>>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h >>>> index bb5636cc17b91a7..b068dfc5f2ef0ab 100644 >>>> --- a/include/linux/blkdev.h >>>> +++ b/include/linux/blkdev.h >>>> @@ -949,11 +949,12 @@ static inline struct request_queue *bdev_get_queue(struct block_device *bdev) >>>> * multiple of 512 bytes. Hence these two constants. >>>> */ >>>> #ifndef SECTOR_SHIFT >>>> -#define SECTOR_SHIFT 9 >>>> +#define SECTOR_SHIFT 9 >>>> #endif >>>> #ifndef SECTOR_SIZE >>>> -#define SECTOR_SIZE (1 << SECTOR_SHIFT) >>>> +#define SECTOR_SIZE (1 << SECTOR_SHIFT) >>>> #endif >>>> +#define PAGE_SECTORS (PAGE_SIZE / SECTOR_SIZE) >>>> >>>> /* >>>> * blk_rq_pos() : the current sector >>> [snipped] >>> >>> >> > > > . >