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 212318489; Mon, 3 Mar 2025 17:24:15 +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=1741022656; cv=none; b=Xig9MK8l7h6O3Krx7Lfa+ma6EjJuGeZjcZJbKe40QvRR5fEB971huwX9nfYTbs2p692QbcPr4TQrJxZCVF74zpqhghYJ85Vw+IY3+zm4v2PB5WN1UR9SBZOy7hT+MB9PMuRbO/1PBEEmkDX0nJvkzV1bVmZ5x9dfW9x0UiGE09Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741022656; c=relaxed/simple; bh=C2ckK8bQNDcbcsSG2G21/Gbr8CgvuAOuCYZlkUnoJzM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=eLSij6ixTublHiZClU7uHdwSdAF3wyK1NYXuNVhuhpIKlcPvmzQPVvspki70lJ5PBtZWz1SulDivKiAcPN4mLpKpEem3sn7ICShM20eTwmND7RfzbVynDDjb3Y7PyP7P7SegYA+1P4/uC68cepMUyukwbqAd69zduIEzN3Bves0= 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=4uQGxSas; 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="4uQGxSas" 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=W8TcBwyxADhLGVfNgYnLKlgRAFc493awa18FegwhHx8=; b=4uQGxSasnvdUe0VwB9hxz63WQu O3W5iHQirJAb0LlJ8nST9aR2VPRfy9NVZH/b9AmAl06WsDr6iWozOdBQvOBikaxrDwhITAvKXEBGR 4k1Os81aX6xhVZ/FIvp2o+36HOxMHXO15SORYtaLWUU6+1vxPeWeqwtgjuEDnpYoSL3h/G701zhdR FpP9PBBgEH7VzhG8ATqt9zkazF5zF+5C62CX3OV+VUN2JlZ2NOX2PTDgmyDxrup65AILiFJrt0WeX b9VDVuolET3U2wU/HKpZzOSTUN9MkHkV2+Wg5saBndPjAv+H6ksAFPvbX9XDzesHxjrxVf694SE6g EdqvXLgA==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tp9WX-00000001jSm-2duk; Mon, 03 Mar 2025 17:24:13 +0000 Date: Mon, 3 Mar 2025 09:24:13 -0800 From: Christoph Hellwig To: Mikulas Patocka Cc: Christoph Hellwig , Jens Axboe , Jooyung Han , Alasdair Kergon , Mike Snitzer , Heinz Mauelshagen , 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-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: 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 05:16:48PM +0100, Mikulas Patocka wrote: > What should I use instead of bmap? Is fiemap exported for use in the > kernel? You can't do an ahead of time mapping. It's a broken concept. > Would Jens Axboe agree to merge the dm-loop logic into the existing loop > driver? What logic? > Dm-loop is significantly faster than the regular loop: > > # modprobe brd rd_size=1048576 > # dd if=/dev/zero of=/dev/ram0 bs=1048576 > # mkfs.ext4 /dev/ram0 > # mount -t ext4 /dev/ram0 /mnt/test > # dd if=/dev/zero of=/mnt/test/test bs=1048576 count=512 All of this needs to be in a commit log. Also note that the above: a) does not use direct I/O which any sane loop user should b) is not on a file but a block device, rendering the use of a loop device entirely pointless.