From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 04/23] vfs: Introduce infrastructure for revoking a file Date: Wed, 3 Jun 2009 08:38:15 +0200 Message-ID: <20090603063815.GE27563@wotan.suse.de> References: <1243893048-17031-4-git-send-email-ebiederm@xmission.com> <20090602071411.GE31556@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Al Viro , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins , Tejun Heo , Alexey Dobriyan , Linus Torvalds , Alan Cox , Greg Kroah-Hartman , Andrew Morton , Christoph Hellwig , "Eric W. Biederman" To: "Eric W. Biederman" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:55775 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751351AbZFCGiO (ORCPT ); Wed, 3 Jun 2009 02:38:14 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Jun 02, 2009 at 03:56:02PM -0700, Eric W. Biederman wrote: > Nick Piggin writes: > > >> In addition for a complete solution we need: > >> - A reliable way the file structures that we need to revoke. > >> - To wait for but not tamper with ongoing file creation and cleanup. > >> - A guarantee that all with user space controlled duration are removed. > >> > >> The file_hotplug_lock has a very unique implementation necessitated by > >> the need to have no performance impact on existing code. Classic locking > > > > Well, it isn't no performance impact. Function calls, branches, icache > > and dcache... > > Practically none. OK that's different from none. There is obviously overhead.