From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bharata B Rao Subject: Re: [RFC] Union mount readdir support in glibc Date: Wed, 12 Mar 2008 09:58:58 +0530 Message-ID: <20080312042858.GB16709@in.ibm.com> References: <20080311055527.GA7256@in.ibm.com> <20080311080929.B076D26F991@magilla.localdomain> Reply-To: bharata@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: libc-alpha@sourceware.org, Jan Blunck , Erez Zadok , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, Christoph Hellwig , Ulrich Drepper , Mingming Cao , Dave Hansen To: Roland McGrath Return-path: Received: from e4.ny.us.ibm.com ([32.97.182.144]:45121 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751799AbYCLE3F (ORCPT ); Wed, 12 Mar 2008 00:29:05 -0400 Content-Disposition: inline In-Reply-To: <20080311080929.B076D26F991@magilla.localdomain> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Mar 11, 2008 at 01:09:29AM -0700, Roland McGrath wrote: > > This really is the kernel filesystem's problem. It just doesn't make sense > to expect userland to implement half of your directory semantics for you. I agree that we are asking glibc to handle part of the union mount semantics in readdir. But we have tried handling directory listing of union entirely inside the kernel, but the results haven't been so good. (http://lkml.org/lkml/2007/12/5/147). Recently Al Viro suggested that we do this in the userland and he felt that is the only sane way of doing this. Infact I had mentioned about this approach to Ulrich briefly during FOSS.IN and he sounded positive to the idea of maintaining a dirent cache for duplicate elimination as long as it doesn't slowdown normal users. Regards, Bharata.