From mboxrd@z Thu Jan 1 00:00:00 1970 From: jim owens Subject: Re: [PATCH 1/3] fs: Document the reflink(2) system call. Date: Tue, 05 May 2009 19:08:07 -0400 Message-ID: <4A00C6D7.9040308@hp.com> References: <1241331303-23753-1-git-send-email-joel.becker@oracle.com> <1241331303-23753-2-git-send-email-joel.becker@oracle.com> <20090505010703.GA12731@shareable.org> <20090505071608.GB10258@mail.oracle.com> <20090505130114.GD17486@mit.edu> <20090505170058.GD7835@mail.oracle.com> <20090505223016.GF7574@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Theodore Tso , linux-fsdevel@vger.kernel.org, jmorris@namei.org, ocfs2-devel@oss.oracle.com, viro@zeniv.linux.org.uk To: Jamie Lokier , joel.becker@oracle.com Return-path: Received: from g1t0026.austin.hp.com ([15.216.28.33]:25368 "EHLO g1t0026.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752774AbZEEXIM (ORCPT ); Tue, 5 May 2009 19:08:12 -0400 In-Reply-To: <20090505223016.GF7574@shareable.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Jamie Lokier wrote: > But assuming it stays shared until you modify the actual data, could > the documentation make this important fact a bit more prominent: > Opening a file, reading it, read-only or private mappings, and > simple attribute updates (chown, chmod, futimes, as well as > automatic atime updates) will not trigger copy-on-write and will > not return ENOSPC errors. almost... more like: automatic atime updates) will not trigger file data copy-on-write and will not return ENOSPC errors unless the filesytem would have returned ENOSPC if the file had no reflink. filesystems such as btrfs that COW metadata changes can generate ENOSPC on any attribute update! jim