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, 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 2377DC64E7A for ; Fri, 27 Nov 2020 15:36:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9CBCC20795 for ; Fri, 27 Nov 2020 15:36:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9CBCC20795 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AFDBC6B006E; Fri, 27 Nov 2020 10:36:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id AAF596B0070; Fri, 27 Nov 2020 10:36:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9C3546B0071; Fri, 27 Nov 2020 10:36:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0219.hostedemail.com [216.40.44.219]) by kanga.kvack.org (Postfix) with ESMTP id 8236F6B006E for ; Fri, 27 Nov 2020 10:36:21 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 455DD1EF1 for ; Fri, 27 Nov 2020 15:36:21 +0000 (UTC) X-FDA: 77530599762.13.drink62_2c02ead27389 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 226B218140B60 for ; Fri, 27 Nov 2020 15:36:21 +0000 (UTC) X-HE-Tag: drink62_2c02ead27389 X-Filterd-Recvd-Size: 2281 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Fri, 27 Nov 2020 15:36:20 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 5CA0168B05; Fri, 27 Nov 2020 16:36:16 +0100 (CET) Date: Fri, 27 Nov 2020 16:36:15 +0100 From: Christoph Hellwig To: Jan Kara Cc: Christoph Hellwig , Jens Axboe , Tejun Heo , Josef Bacik , Coly Li , Mike Snitzer , Greg Kroah-Hartman , Johannes Thumshirn , dm-devel@redhat.com, Jan Kara , linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Chao Yu Subject: Re: [PATCH 37/44] block: switch partition lookup to use struct block_device Message-ID: <20201127153615.GA7524@lst.de> References: <20201126130422.92945-1-hch@lst.de> <20201126130422.92945-38-hch@lst.de> <20201126182219.GC422@quack2.suse.cz> <20201127094842.GA15984@lst.de> <20201127124537.GC27162@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201127124537.GC27162@quack2.suse.cz> User-Agent: Mutt/1.5.17 (2007-11-01) 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, Nov 27, 2020 at 01:45:37PM +0100, Jan Kara wrote: > > At this point the hd_struct is already allocated together with the > > block_device, and thus only freed after the last block_device reference > > goes away plus the inode freeing RCU grace period. So the device model > > ref to part is indeed gone, but that simply does not matter any more. > > Well, but once device model ref to part is gone, we're going to free the > bdev inode ref as well. Thus there's nothing which pins the bdev containing > hd_struct? > > But now as I'm thinking about it you later switch the device model reference > to just pure inode reference and use igrab() which will reliably return > NULL if the inode is on it's way to be destroyed so probably we are safe in > the final state. igrab always succeeds. But we should switch to a tryget.