Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752265Ab1CYDvY (ORCPT ); Thu, 24 Mar 2011 23:51:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39672 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864Ab1CYDvX (ORCPT ); Thu, 24 Mar 2011 23:51:23 -0400 Date: Thu, 24 Mar 2011 23:47:11 -0400 From: Chuck Ebbert To: Denys Vlasenko Cc: linux-kernel@vger.kernel.org, Alexander Viro , Roman Borisov , Alexander Shishkin Subject: Re: 2.6.35-rc4: mount results with and without MS_SILENT differ Message-ID: <20110324234711.60a6e3c3@katamari> In-Reply-To: <201103140520.08737.vda.linux@googlemail.com> References: <201103140520.08737.vda.linux@googlemail.com> Organization: Red Hat, Inc. Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1867 Lines: 55 On Mon, 14 Mar 2011 05:20:08 +0100 Denys Vlasenko wrote: It looks like this bug has been there forever. This fails: > mount -vv --make-rshared mount.shared1 2>&1 This succeeds: > mount -vv --loud --make-rshared mount.shared2 2>&1 # <-HERE Failure case uses MS_REC | MS_SHARED | MS_SILENT > mount: mount('','mount.shared1','',0x0010c000,''):0 It succeeds with MS_REC | MS_SHARED > mount: mount('','mount.shared2','',0x00104000,''):0 Looking at do_mount() we see some flags get filtered out before checking namespace flags: flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | MS_STRICTATIME); Then: else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&path, flags); In do_change_type() type = flags_to_propagation_type(flag); if (!type) return -EINVAL; And flags_to_propagation_type() filters out MS_REC before making sure one and only one of the propagation type flags is set: int type = flags & ~MS_REC; /* Fail if any non-propagation flags are set */ if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) return 0; /* Only one propagation flag should be set */ if (!is_power_of_2(type)) return 0; Looks like the is_power_of_2() test is failing because MS_SILENT is set. I'm not sure whether to filter MS_SILENT in the upper or lower function though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/