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 25E9C18A6DB for ; Wed, 22 Jan 2025 07:37:39 +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=1737531461; cv=none; b=RSxBx0nedMWKNcFz+r9z4grDjNUhbpY0QVtUwku7kcK4IKWynsA+YI/2p9j55kiFD2LopNJA5sk9ihRwKYb7YezgPEZ7U+ap4Z+SAI3xry/ULBjaKJISsZ6rISpv1iKNbfMPOYUryBREbKPreQVxWloj4vQUlnCMhArQChKMXTc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737531461; c=relaxed/simple; bh=VMatHh+dZNa9EN6xiV8VNTX48LNysiTR7osEuaSDqZM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YU9PnahvRvgnjGKwjevCAKO7EWn/WWEtMIHf+VzWI0pKa2tdImBxMJhKkhUMGUBuVPZVUm62X2+3iWnkPTykEYeozS1nN1Ia8ab5CIxlV5wyK3YHPMIkxt1x46uNlh+R5KuBAhLWVCCq8sd/RzjFMra/kvbRgSNxziuYjyBXG/g= 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=3rZ4qLal; 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="3rZ4qLal" 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=WRBW9g7osOhBN86koWamWVCWvBItcnFJBMhYw4GC8bo=; b=3rZ4qLal1XWG03XEgg832qzWtk XO2TXf3q9knYeWjZRyAQUqlaCE1xaPLElOngdiH2HD9YyrdXpN0tSUcyjTkDJMD+i/sH6g6EJwjLy Tz0zZURgDbbuz4r6KcWvVlkyx4KSxeGrdwr/dP9ksxdXwQ8EnirS7XkOLWa3nxNMcw2REzyZaG3jk +T2k16CL4NO2KnCA1iUWvYekXFqVTS+MRHbs4lXUqYCZFQHnFoWa9akhw64FjbRtur6nvv5ziCk0V WWLBX9iLLSy/NfZcuerP/LrV3TjDx8UgTj/NUQ4nHDKu39/qLYaLZuO3DHLY9mrpsJN606AW9rmgf WRoq2MMQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1taVIw-00000009bm7-1zYl; Wed, 22 Jan 2025 07:37:38 +0000 Date: Tue, 21 Jan 2025 23:37:38 -0800 From: Christoph Hellwig To: Gerhard Wiesinger Cc: Theodore Ts'o , linux-ext4@vger.kernel.org Subject: Re: Transparent compression with ext4 - especially with zstd Message-ID: References: <8cb4d855-6bd8-427f-ac8f-8cf7b91547fb@wiesinger.com> <20250121040125.GC3761769@mit.edu> <213343dc-3911-45de-8195-469da9dd1a91@wiesinger.com> <20250121193351.GA3820043@mit.edu> Precedence: bulk X-Mailing-List: linux-ext4@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 Wed, Jan 22, 2025 at 08:29:09AM +0100, Gerhard Wiesinger wrote: > BTW: Why does it break the ACID properties? It doesn't if implemented properly, which of course means out of place writes. The only sane way to implement compression in XFS would be using out of place writes, which we support for reflinks and which is heavily used by the new zoned mode. For the latter retrofitting compression would be relatively easy, but it first needs to get merged, then stabilize and mature, and then we'll need to see if we have enough use cases. So don't plan for it.