From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from resqmta-po-09v.sys.comcast.net ([96.114.154.168]:39323 "EHLO resqmta-po-09v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750845AbaLWAIO (ORCPT ); Mon, 22 Dec 2014 19:08:14 -0500 Message-ID: <5498B26C.5010908@pobox.com> Date: Mon, 22 Dec 2014 16:08:12 -0800 From: Robert White MIME-Version: 1.0 To: Richard Sharpe CC: Austin S Hemmelgarn , Chris Murphy , Btrfs BTRFS Subject: Re: Can BTRFS handle XATTRs larger than 4K? References: <54982A79.1090102@gmail.com> <54985E4C.40003@gmail.com> <5498829E.3060608@gmail.com> <5498A0BD.3000300@pobox.com> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 12/22/2014 02:55 PM, Richard Sharpe wrote: > On Mon, Dec 22, 2014 at 2:52 PM, Robert White wrote: >> So skipping the full ADS, what's the current demand/payoff for large XATTR space? > > Windows Security Descriptors (sometimes incorrectly called ACLs) > stored by Samba. Ah. I know that Linux ACLs are fairly small per entry, I take it Windows' can be much bigger? Having just gone off an read a lot about the many ADS possible in windows, they've sort of treated ever file as if it were the name of a phantom directory limited depth... That is you seem to be able to create any name as a stream name but you can't create any pathname as same. The system-level API -- that is the complete retooling of SYS_open et al -- and the requsite departure from POSIX -- seems unlikely. On the antipode, it seems like being able to put an inode reference key type (e.g. a name,inode pair as one of the metadata entries) could relieve the space constraint for a limited number of entires. The contents of that inode's data region would become the value of the single attribute. Does that relieve Security Descriptor burden? Is each descriptor a separate attribute or are all the descriptors held in one attribute as a list-of? Going full "phantom directory" to match Windows just seems like we get into the business of replacing whole kernel tidbits a la the inner-system effect.