From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 2B1977F77 for ; Sat, 1 Aug 2015 08:01:35 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay3.corp.sgi.com (Postfix) with ESMTP id C7E08AC001 for ; Sat, 1 Aug 2015 06:01:31 -0700 (PDT) Received: from josefsipek.net (josefsipek.net [71.174.113.7]) by cuda.sgi.com with ESMTP id HrvPLCqYspxaqt6H for ; Sat, 01 Aug 2015 06:01:30 -0700 (PDT) Date: Sat, 1 Aug 2015 09:01:31 -0400 From: Josef 'Jeff' Sipek Subject: Re: [RFC v2 00/24] xfs: add reflink and dedupe support Message-ID: <20150801130131.GD101746@meili.valhalla.31bits.net> References: <20150729223258.17414.91354.stgit@birch.djwong.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20150729223258.17414.91354.stgit@birch.djwong.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: "Darrick J. Wong" Cc: xfs@oss.sgi.com On Wed, Jul 29, 2015 at 03:32:59PM -0700, Darrick J. Wong wrote: > Hi all, > > This is the second revision of an RFC for adding to XFS kernel support > for mapping multiple file logical blocks to the same physical block, > more commonly known as reflinking. The implementation a single [block > range, refcount] tree to track the reference counts of extents of > physical blocks. There's also support code to provide the desired > copy-on-write behavior and the userland interfaces to reflink, query > the status of, and un-reflink files. This is cool work. I have a random thought to share... IIRC, you keep a per-inode flag to avoid expensive ops on files that have no refcounted blocks. ZFS keeps a bit in each block pointer to indicate that the target is dedup'd. I'd have to check if xfs has a spare bit in its block pointer, but if it does that's one way to minimize the refcount btree overhead. Jeff. -- mainframe, n.: An obsolete device still used by thousands of obsolete companies serving billions of obsolete customers and making huge obsolete profits for their obsolete shareholders. And this year's run twice as fast as last year's. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs