From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 543943C00; Mon, 3 Mar 2025 17:24:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741022693; cv=none; b=aihtsNJYfMTTNp7eeGCRaDSYjkmx1WM3yoW/LLqWNWqFRY8inRKq4vtUBRDjsmzrk797OiAuJNw7cO/VGb4O1CBW3IA7wV0+EC+mrkbw3H7eWLrHvN6TcUrU08l9jlOku2GisT+LMf2NfN7YxuVMnyRcVfK+4fPs6MaOWTe0FnU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741022693; c=relaxed/simple; bh=BBXIeF3s4cWm1soZ0YqK9pYdpjsklMIOiJu8xjo7k2s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PuEatxMb95SGzsgJjOFvJAlrLm18UWw0Njn7g0ypmU/Nb8/JdOnD1w2tM1KX0c+Ymj3bK2RX1chewuWL/V4qfR+A7ipZizHcz1+Zmq6YT8hWAkIh64WCO3Elt8xMMZIi9pGGVJ5Egy6TeQ9ApHOYt4Shef4g8V/cvEmdv547S4Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=zc6RJe2Q; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="zc6RJe2Q" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=HkSuV/vGaF5uKZu66/cVbxyXHK2ocanHIOHlW07RMXE=; b=zc6RJe2Q3P/PR/6udZth9WSORF PGFiQHy3t+wMaX7UwZXuQDy4iJjFEbrhweTBfZMbSQirw5I+PDIMYQ0f/9NziA6cihazsg7AwFpSq MS5ntvw5JebPKFI0pZcChGu8FjvcZxpzI5kSvxSFz4r+Lr2DdZQULU1NZ954WMzppEMuvJ3ocxgXI fJopaqkTvxnr4RRTSppLXNfJXKLQ+AI0Mo+7qVsjuFv97LL/uxLlFUKjG6nlLpxYw9KfU5GEC9EaG VmwlzwHYWfZWXNBxE/uvCnhY68CosOJS/z6BlJBxHvsOVBwKW9RO28IfO6Cd2T3aGymnn1/Fe/zlu XNHqpUMQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tp9X8-00000001jb1-3goI; Mon, 03 Mar 2025 17:24:50 +0000 Date: Mon, 3 Mar 2025 09:24:50 -0800 From: Christoph Hellwig To: Heinz Mauelshagen Cc: Christoph Hellwig , Mikulas Patocka , Jooyung Han , Alasdair Kergon , Mike Snitzer , zkabelac@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] the dm-loop target Message-ID: References: <7d6ae2c9-df8e-50d0-7ad6-b787cb3cfab4@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Mar 03, 2025 at 05:06:16PM +0100, Heinz Mauelshagen wrote: > On Mon, Mar 3, 2025 at 4:24 PM Christoph Hellwig wrote: > > > On Mon, Mar 03, 2025 at 03:57:23PM +0100, Heinz Mauelshagen wrote: > > > dm-loop avoids the file system abstraction, thus gains the resulting > > > performance advantage versus the loop driver. > > > > How? > > > > It uses a predefined map and thus avoids VFS -> FS write path overhead > completelly. But you simply can't use a "pre-defined map". It's fundamentally unsafe. > The inode fiemap() operation would avoid issues relative to outdated bmap(). No, using that for I/O is even worse.