From: Christoph Hellwig Subject: Re: [PATCH 0/4][RFC] NFSv3: implement extended attribute (XATTR) protocol Date: Tue, 22 Sep 2009 08:47:55 -0400 Message-ID: <20090922124755.GA2886@infradead.org> References: <4AB51538.7060201@schaufler-ca.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Casey Schaufler , Trond Myklebust , "J. Bruce Fields" , linux-nfs@vger.kernel.org, Christoph Hellwig , linux-fsdevel@vger.kernel.org To: James Morris Return-path: In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sun, Sep 20, 2009 at 03:13:28PM +1000, James Morris wrote: > As a first step, it keeps the semantics simple, and provides a direct > mapping between the userland API and the NFS protocol. System level > xattrs may have semantics which extend beyond the simple NFS xattr > protocol (e.g. full security labeling as we've previously discussed & > documented needs to convey more than just object labels). > > Some xattr uses are internal local interfaces, such as with Linux ACLs, > where xattrs are used internally for storing the ACL data, but the exposed > API is quite different (as is the NFS protocol). > > We can go beyond user.*, but I think each system-level xattr exposed via > NFS will need to be considered on a case-by-case basis. Note that the mapping should be really simple. Both the NFS protocol and XFS implement the same IRIX-xattr format that has a numerical namespace instead of the string prefix Linux has. If you just use the same mapping as XFS it should not have interoperability problems.