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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 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 In-Reply-To: <20201127153615.GA7524@lst.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-loop: dm-devel@redhat.com Cc: Jens Axboe , Chao Yu , Jan Kara , Mike Snitzer , linux-mm@kvack.org, Greg Kroah-Hartman , Jan Kara , Josef Bacik , Coly Li , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, dm-devel@redhat.com, linux-mtd@lists.infradead.org, Johannes Thumshirn , Tejun Heo , linux-bcache@vger.kernel.org Subject: Re: [dm-devel] [PATCH 37/44] block: switch partition lookup to use struct block_device X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel