From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755447AbbCEMK0 (ORCPT ); Thu, 5 Mar 2015 07:10:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51470 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751868AbbCEMKY (ORCPT ); Thu, 5 Mar 2015 07:10:24 -0500 Date: Thu, 5 Mar 2015 13:10:10 +0100 From: Karel Zak To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , Sergey Senozhatsky , Nitin Gupta , linux-kernel@vger.kernel.org, Jerome Marchand Subject: Re: [PATCH 0/2] make automatic device_id generation possible Message-ID: <20150305121010.GY8046@ws.net.home> References: <1425478601-19141-1-git-send-email-sergey.senozhatsky@gmail.com> <20150305001954.GA9563@blaptop> <20150305005829.GC14927@swordfish> <20150305012043.GD14927@swordfish> <20150305013301.GA5041@blaptop> <20150305014752.GF14927@swordfish> <20150305020436.GB5041@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150305020436.GB5041@blaptop> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 05, 2015 at 11:04:36AM +0900, Minchan Kim wrote: > On Thu, Mar 05, 2015 at 10:47:52AM +0900, Sergey Senozhatsky wrote: > > On (03/05/15 10:33), Minchan Kim wrote: > > > > hm, I can think of a huge build server with tons of users. /dev/zram$(id -u) > > > > created during user login and destroyed during logout. so users use theirs own > > > > zram devices with predictable device ids (which also makes it simpler for admin) > > > > for compilation/etc., and don't pressure hdds that much. > > > > > > They upgraded the system and from now on, one of app tries automatic > > > id with zram for some reason. What happens if he gets some user id > > > before the user login? The system should have fallback in the case of > > > failing to create own userid assignment. > > > > we upgraded our scripts but landed some bugs there? it's up to particular > > implementation. in your example, I assume, someone used zram with num_devices >= 1000? > > that's impossible. current num_devices limitation is 32. and uid-s start from 1000. > > I meant it. > If we support use-defined id and someone have used your idea so he can make zram > per-user as uid. After a while, new application stats automatic id assignment > so upcoming users can consume upcoming user id. yeah, automaic id will start > from 0 so it's very rare to reach 1000 but who knows? Why 1000? The UID_MIN and UID_MAX is nothing strictly defined, it's just option in /etc/login.defs. I guess it's nothing unusually to have system where UID_MIN is 500 :-) Karel -- Karel Zak http://karelzak.blogspot.com