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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 2E9BBC5519F for ; Fri, 20 Nov 2020 10:53:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8F60A20657 for ; Fri, 20 Nov 2020 10:53:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F60A20657 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E2EE26B006C; Fri, 20 Nov 2020 05:53:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DDFC16B006E; Fri, 20 Nov 2020 05:53:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CF4AE6B0070; Fri, 20 Nov 2020 05:53:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0188.hostedemail.com [216.40.44.188]) by kanga.kvack.org (Postfix) with ESMTP id 96DEC6B006C for ; Fri, 20 Nov 2020 05:53:22 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 138AD181AEF1D for ; Fri, 20 Nov 2020 10:53:22 +0000 (UTC) X-FDA: 77504485044.15.peace10_1316fdc2734a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id E58981814B0C7 for ; Fri, 20 Nov 2020 10:53:21 +0000 (UTC) X-HE-Tag: peace10_1316fdc2734a X-Filterd-Recvd-Size: 3115 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Nov 2020 10:53:21 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 015E9AED9; Fri, 20 Nov 2020 10:53:20 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id AC96F1E130B; Fri, 20 Nov 2020 11:53:19 +0100 (CET) Date: Fri, 20 Nov 2020 11:53:19 +0100 From: Jan Kara To: Christoph Hellwig Cc: Jan Kara , Jens Axboe , Tejun Heo , Josef Bacik , Konrad Rzeszutek Wilk , Coly Li , Mike Snitzer , dm-devel@redhat.com, Richard Weinberger , Jan Kara , linux-block@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 15/20] block: merge struct block_device and struct hd_struct Message-ID: <20201120105319.GA15537@quack2.suse.cz> References: <20201118084800.2339180-1-hch@lst.de> <20201118084800.2339180-16-hch@lst.de> <20201119143921.GX1981@quack2.suse.cz> <20201120091546.GE21715@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201120091546.GE21715@lst.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 20-11-20 10:15:46, Christoph Hellwig wrote: > On Thu, Nov 19, 2020 at 03:39:21PM +0100, Jan Kara wrote: > > This patch is kind of difficult to review due to the size of mostly > > mechanical changes mixed with not completely mechanical changes. Can we > > perhaps split out the mechanical bits? E.g. the rq->part => rq->bdev > > renaming is mechanical and notable part of the patch. Similarly the > > part->foo => part->bd_foo bits... > > We'd end with really weird patches that way. Never mind that I'm not > even sure how we could mechnically do the renaming. Well, I believe coccinelle should be able to do the renaming automatically. > > Also I'm kind of wondering: AFAIU the new lifetime rules, gendisk holds > > bdev reference and bdev is created on gendisk allocation so bdev lifetime is > > strictly larger than gendisk lifetime. But what now keeps bdev->bd_disk > > reference safe in presence device hot unplug? In most cases we are still > > protected by gendisk reference taken in __blkdev_get() but how about > > disk->lookup_sem and disk->flags dereferences before we actually grab the > > reference? > > Good question. I'll need to think about this a bit more. My thinking was that you could use kobject_get_unless_zero(bdev->bd_device->kobj) and after you hold this reference, you can do everything else safely. In this case it is really useful that device is embedded in block_dev and not in gendisk itself... Honza -- Jan Kara SUSE Labs, CR