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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 8D5D4CA9EC9 for ; Tue, 5 Nov 2019 00:17:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 604E420650 for ; Tue, 5 Nov 2019 00:17:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Z+Zg46Ed" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387631AbfKEARb (ORCPT ); Mon, 4 Nov 2019 19:17:31 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:38718 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387415AbfKEARa (ORCPT ); Mon, 4 Nov 2019 19:17:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=rmotbuiJ0EOix30Si2XGpOoKC4o3ZoK8589mQ5Hds5I=; b=Z+Zg46Edx1IcEww0YGj1D014Y FAP0eWgSKwkaX082En4iPK1lkJ+QJtwwfyIMKmG9lPkKZOY+OclgDKegBaxvhmpLyhQ23jjLmFugA oLeq/gTRdbv1iobQhOgF6CK5YOZfYCteiEk1svh+/8LNHIrJgADgMOjXWcPB7q6wq4L8H+EFqPqCE HAevx5CCOKSk4Z1PTMBZs82iMD5dGMA5OSvNy2zEU+EQHavbOD9WQrwQ56n7a8fJrg1sJPeAB7hH4 ivlzDonGWMNApnCNtnkVouVVtvyh7SRwdWiS4fuapBmULFF/eaM3uZ8yV0Ypqz+N7VsYNP7cYPO3C Ui4wppx3w==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1iRmXH-0007vi-Ay; Tue, 05 Nov 2019 00:17:27 +0000 Date: Mon, 4 Nov 2019 16:17:27 -0800 From: Christoph Hellwig To: Michal Suchanek Cc: linux-scsi@vger.kernel.org, Christoph Hellwig , Matthew Wilcox , "Ewan D. Milne" , Jonathan Corbet , Jens Axboe , "James E.J. Bottomley" , "Martin K. Petersen" , Alexander Viro , "J. Bruce Fields" , Mauro Carvalho Chehab , Eric Biggers , Benjamin Coddington , Hannes Reinecke , Omar Sandoval , Ming Lei , Damien Le Moal , Bart Van Assche , Tejun Heo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v3 5/7] bdev: add open_finish. Message-ID: <20191105001727.GA29826@infradead.org> References: <31f640791d9cc20cdbbb3000dfcf8370cf3c6223.1572002144.git.msuchanek@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <31f640791d9cc20cdbbb3000dfcf8370cf3c6223.1572002144.git.msuchanek@suse.de> User-Agent: Mutt/1.12.1 (2019-06-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Please make sure you CC linux-block if you add block device ops. On Fri, Oct 25, 2019 at 01:21:42PM +0200, Michal Suchanek wrote: > Opening a block device may require a long operation such as waiting for > the cdrom tray to close. Performing this operation with locks held locks > out other attempts to open the device. These processes waiting to open > the device are not killable. > > To avoid this issue and still be able to perform time-consuming checks > at open() time the block device driver can provide open_finish(). If it > does opening the device proceeds even when an error is returned from > open(), bd_mutex is released and open_finish() is called. If > open_finish() succeeds the device is now open, if it fails release() is > called. > > When -ERESTARTSYS is returned from open() blkdev_get may loop without > calling open_finish(). On -ERESTARTSYS open_finish() is not called. > > Move a ret = 0 assignment up in the if/else branching to avoid returning > -ENXIO. Previously the return value was ignored on the unhandled branch. Still a complete nack for splitting a fundamental operation over two ops, especially just for working around a piece of buggy software.