From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [patch 26/28] netconsole: Support dynamic reconfiguration using configfs Date: Fri, 10 Aug 2007 15:35:23 -0700 (PDT) Message-ID: <20070810.153523.57443099.davem@davemloft.net> References: <200708102112.l7ALC9oD009457@imap1.linux-foundation.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, satyam@infradead.org, Joel.Becker@oracle.com, k-keiichi@bx.jp.nec.com, mpm@selenic.com To: akpm@linux-foundation.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:34768 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753424AbXHJWfX (ORCPT ); Fri, 10 Aug 2007 18:35:23 -0400 In-Reply-To: <200708102112.l7ALC9oD009457@imap1.linux-foundation.org> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: akpm@linux-foundation.org Date: Fri, 10 Aug 2007 14:12:09 -0700 > From: Satyam Sharma > > Based upon initial work by Keiichi Kii . > > This patch introduces support for dynamic reconfiguration (adding, removing > and/or modifying parameters of netconsole targets at runtime) using a > userspace interface exported via configfs. Documentation is also updated > accordingly. > > Issues and brief design overview: > > (1) Kernel-initiated creation / destruction of kernel objects is not > possible with configfs -- the lifetimes of the "config items" is managed > exclusively from userspace. But netconsole must support boot/module > params too, and these are parsed in kernel and hence netpolls must be > setup from the kernel. Joel Becker suggested to separately manage the > lifetimes of the two kinds of netconsole_target objects -- those created > via configfs mkdir(2) from userspace and those specified from the > boot/module option string. This adds complexity and some redundancy here > and also means that boot/module param-created targets are not exposed > through the configfs namespace (and hence cannot be updated / destroyed > dynamically). However, this saves us from locking / refcounting > complexities that would need to be introduced in configfs to support > kernel-initiated item creation / destroy there. > > (2) In configfs, item creation takes place in the call chain of the > mkdir(2) syscall in the driver subsystem. If we used an ioctl(2) to > create / destroy objects from userspace, the special userspace program is > able to fill out the structure to be passed into the ioctl and hence > specify attributes such as local interface that are required at the time > we set up the netpoll. For configfs, this information is not available at > the time of mkdir(2). So, we keep all newly-created targets (via > configfs) disabled by default. The user is expected to set various > attributes appropriately (including the local network interface if > required) and then write(2) "1" to the "enabled" attribute. Thus, > netpoll_setup() is then called on the set parameters in the context of > _this_ write(2) on the "enabled" attribute itself. This design enables > the user to reconfigure existing netconsole targets at runtime to be > attached to newly-come-up interfaces that may not have existed when > netconsole was loaded or when the targets were actually created. All this > effectively enables us to get rid of custom ioctls. > > (3) Ultra-paranoid configfs attribute show() and store() operations, with > sanity and input range checking, using only safe string primitives, and > compliant with the recommendations in Documentation/filesystems/sysfs.txt. > > (4) A new function netpoll_print_options() is created in the netpoll API, > that just prints out the configured parameters for a netpoll structure. > netpoll_parse_options() is modified to use that and it is also exported to > be used from netconsole. > > Signed-off-by: Satyam Sharma > Acked-by: Keiichi Kii > Cc: Matt Mackall > Cc: Joel Becker > Signed-off-by: Andrew Morton This looks good to me, applied to net-2.6.24, thanks!