From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 37FE41EB36 for ; Mon, 6 Nov 2023 12:25:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="puA6n0Pg" Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D443CA4; Mon, 6 Nov 2023 04:25:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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; bh=L5cl+RDGvEZz/eLwTMy1ZuCPzEPX60KHCPNo+ErIHy4=; b=puA6n0PgFkK0VPgWd7sgpG2sKf OmzKe1XT0YAyimc52KRiAoNH3O7Fhq11tS78bssrVpQO0kvL6mwWtq/FRod5W7JUC08ERJOBDokh+ MGzUkO+0pGktqi7q27y5BrHpvOu9tR6YqvXhowUaDtSyN2QKyY2LKR6R/L7bVW4o+sn7pfzf2c11+ 3n4D480mji01XbaZ0xulBr9wfUPqoIPCZEWPY5yBnYWeAbOhX3LrtloYWcbZsWaPi/ZoIaNmmbcdv /UqFj568ILBgUbruYDaQs+rjPuAB3sqX5rtvGqU5Wrc/mkdXnCLsXrN0Zc3xYxYJuArzoeFfAYDP6 OfTe6/lA==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qzyfc-00GdBF-0X; Mon, 06 Nov 2023 12:25:32 +0000 Date: Mon, 6 Nov 2023 04:25:32 -0800 From: Christoph Hellwig To: Qu Wenruo Cc: Christoph Hellwig , Christian Brauner , Josef Bacik , Qu Wenruo , Amir Goldstein , Jan Kara , Chris Mason , David Sterba , linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 0/3] fanotify support for btrfs sub-volumes Message-ID: References: <20231101-nutzwert-hackbeil-bbc2fa2898ae@brauner> <590e421a-a209-41b6-ad96-33b3d1789643@gmx.com> <20231101-neigen-storch-cde3b0671902@brauner> <20231102051349.GA3292886@perftesting> <20231102-schafsfell-denkzettel-08da41113e24@brauner> <20231103-kursleiter-proklamieren-aae0a02aa1a4@brauner> <1d08a205-b2c5-4276-b271-088facc142ea@suse.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d08a205-b2c5-4276-b271-088facc142ea@suse.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Nov 06, 2023 at 06:48:11PM +1030, Qu Wenruo wrote: > > st_dev has only been very historically about treating something as > > a device. For userspae the most important part is that it designates > > a separate domain for inode numbers. And that's something that's simply > > broken in btrfs. > > In fact, I'm not sure if the "treating something as a device" thing is even > correct long before btrfs. It never really has been. There's just two APIs that ever did this, ustat and the old quotactl. Both have been deprecated a long time ago and never hid wide use. > For example, for an EXT4 fs with external log device. Thankfully it's still > more or less obvious we would use the device number of the main fs, not the > log device, but we already had such examples. More relevant (as the log device never has persistent data) is the XFS realtime device.