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 6F380C3E8C5 for ; Fri, 27 Nov 2020 17:26:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CAA3220786 for ; Fri, 27 Nov 2020 17:26:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CAA3220786 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 52B4C6B0068; Fri, 27 Nov 2020 12:26:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B4856B006C; Fri, 27 Nov 2020 12:26:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3A4796B006E; Fri, 27 Nov 2020 12:26:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0050.hostedemail.com [216.40.44.50]) by kanga.kvack.org (Postfix) with ESMTP id 21A606B0068 for ; Fri, 27 Nov 2020 12:26:44 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id D9B40824999B for ; Fri, 27 Nov 2020 17:26:43 +0000 (UTC) X-FDA: 77530877886.10.eyes15_471154527389 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id BA6E816A069 for ; Fri, 27 Nov 2020 17:26:43 +0000 (UTC) X-HE-Tag: eyes15_471154527389 X-Filterd-Recvd-Size: 2736 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Fri, 27 Nov 2020 17:26:43 +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 E3BEDAE91; Fri, 27 Nov 2020 17:26:41 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E315E1E1319; Fri, 27 Nov 2020 18:26:40 +0100 (CET) Date: Fri, 27 Nov 2020 18:26:40 +0100 From: Jan Kara To: Christoph Hellwig Cc: Jan Kara , 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: <20201127172640.GA4276@quack2.suse.cz> 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> <20201127153615.GA7524@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201127153615.GA7524@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 27-11-20 16:36:15, Christoph Hellwig wrote: > 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. No. If the inode is I_FREEING or I_WILL_FREE, it will return NULL... Honza -- Jan Kara SUSE Labs, CR