From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS Date: Wed, 13 Jun 2007 12:34:05 -0400 Message-ID: <20070613163405.GE28279@think.oraclecorp.com> References: <20070612161029.GB28279@think.oraclecorp.com> <18031.26764.586958.632146@stoffel.org> <20070613103522.GW28279@think.oraclecorp.com> <18031.63640.103936.137412@stoffel.org> <20070613145442.GC28279@think.oraclecorp.com> <18032.5991.475110.794691@stoffel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: John Stoffel Return-path: Received: from agminet01.oracle.com ([141.146.126.228]:20405 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758405AbXFMQiT (ORCPT ); Wed, 13 Jun 2007 12:38:19 -0400 Content-Disposition: inline In-Reply-To: <18032.5991.475110.794691@stoffel.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Jun 13, 2007 at 12:12:23PM -0400, John Stoffel wrote: > >>>>> "Chris" == Chris Mason writes: [ nod ] > Also, I think you're wrong here when you state that making a snapshot > (sub-volume?) RO just requires you to set the quota to 1 block. What > is to stop me from writing 1 block to a random file that already > exists? It's copy on write, so changing one block means allocating a new one and putting the new contents there. The old blocks don't become available for reuse until the transaction commits. -chris