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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B4DBC83005 for ; Wed, 7 Jun 2023 12:17:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240529AbjFGMRL (ORCPT ); Wed, 7 Jun 2023 08:17:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240343AbjFGMRG (ORCPT ); Wed, 7 Jun 2023 08:17:06 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A4A31BD9; Wed, 7 Jun 2023 05:17:03 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id 52B4E6732D; Wed, 7 Jun 2023 14:16:58 +0200 (CEST) Date: Wed, 7 Jun 2023 14:16:58 +0200 From: Christoph Hellwig To: Christian Brauner Cc: Christoph Hellwig , Jens Axboe , Richard Weinberger , Josef Bacik , "Md. Haris Iqbal" , Jack Wang , Phillip Potter , Coly Li , Miquel Raynal , Vignesh Raghavendra , "Martin K. Petersen" , Chris Mason , David Sterba , Alexander Viro , "Rafael J. Wysocki" , Pavel Machek , dm-devel@redhat.com, linux-block@vger.kernel.org, linux-um@lists.infradead.org, linux-scsi@vger.kernel.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, linux-nvme@lists.infradead.org, linux-btrfs@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nilfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 28/31] block: replace fmode_t with a block-specific type for block open flags Message-ID: <20230607121658.GA13632@lst.de> References: <20230606073950.225178-1-hch@lst.de> <20230606073950.225178-29-hch@lst.de> <20230607-kocht-kornfeld-a249c6740e38@brauner> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230607-kocht-kornfeld-a249c6740e38@brauner> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On Wed, Jun 07, 2023 at 11:21:14AM +0200, Christian Brauner wrote: > On Tue, Jun 06, 2023 at 09:39:47AM +0200, Christoph Hellwig wrote: > > The only overlap between the block open flags mapped into the fmode_t and > > other uses of fmode_t are FMODE_READ and FMODE_WRITE. Define a new > > and FMODE_EXCL afaict FMODE_EXCL isn't used outside the block layer and removed in the last patch. > > +blk_mode_t file_to_blk_mode(struct file *file) > > +{ > > + blk_mode_t mode = 0; > > + > > + if (file->f_mode & FMODE_READ) > > + mode |= BLK_OPEN_READ; > > + if (file->f_mode & FMODE_WRITE) > > + mode |= BLK_OPEN_WRITE; > > + if (file->f_mode & FMODE_EXCL) > > + mode |= BLK_OPEN_EXCL; > > + if ((file->f_flags & O_ACCMODE) == 3) > > I really don't like magic numbers like this. I don't like them either, but this is just moved around and not new. > Groan, O_RDONLY being defined as 0 strikes again... > Becuase of this quirk we internally map > > O_RDONLY(0) -> FMODE_READ(1) > O_WRONLY(1) -> FMODE_WRITE(2) > O_RDWR(3) -> (FMODE_READ | FMODE_WRITE) O_RDWR is 2. > so checking for the raw 3 here is confusing in addition to being a magic > number as it could give the impression that what's checked here is > (O_WRONLY | O_RDWR) which doesn't make sense... Well, that is exactly what we check for. This is a 30-ish year old quirk only used in the floppy driver. > So my perference would be in descending order of preference: > > (file->f_flags & O_ACCMODE) == (FMODE_READ | FMODE_WRITE) > > or while a little less clear but informative enough for people familiar > with the O_RDONLY quirk: > > if ((file->f_flags & O_ACCMODE) == O_ACCMODE) I don't understand this part. Especially the above doesn't make any sense as FMODE_READ and FMODE_WRITE are in a completely different symbol space to O_*, and not a UAPŠ† but a kernel internal thing that could be renumbered any time.