From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751330AbXITTyk (ORCPT ); Thu, 20 Sep 2007 15:54:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752008AbXITTxF (ORCPT ); Thu, 20 Sep 2007 15:53:05 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:60156 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938AbXITTxD (ORCPT ); Thu, 20 Sep 2007 15:53:03 -0400 Subject: [PATCH 09/25] make access() use mnt check To: akpm@osdl.org Cc: linux-kernel@vger.kernel.org, hch@infradead.org, Dave Hansen From: Dave Hansen Date: Thu, 20 Sep 2007 12:53:00 -0700 References: <20070920195249.852667D5@kernel> In-Reply-To: <20070920195249.852667D5@kernel> Message-Id: <20070920195300.328EF882@kernel> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org It is OK to let access() go without using a mnt_want/drop_write() pair because it doesn't actually do writes to the filesystem, and it is inherently racy anyway. This is a rare case when it is OK to use __mnt_is_readonly() directly. Acked-by: Christoph Hellwig Signed-off-by: Dave Hansen --- lxc-dave/fs/open.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff -puN fs/open.c~make-access-use-helper fs/open.c --- lxc/fs/open.c~make-access-use-helper 2007-09-20 12:16:13.000000000 -0700 +++ lxc-dave/fs/open.c 2007-09-20 12:16:13.000000000 -0700 @@ -457,8 +457,17 @@ asmlinkage long sys_faccessat(int dfd, c if(res || !(mode & S_IWOTH) || special_file(nd.dentry->d_inode->i_mode)) goto out_path_release; - - if(IS_RDONLY(nd.dentry->d_inode)) + /* + * This is a rare case where using __mnt_is_readonly() + * is OK without a mnt_want/drop_write() pair. Since + * no actual write to the fs is performed here, we do + * not need to telegraph to that to anyone. + * + * By doing this, we accept that this access is + * inherently racy and know that the fs may change + * state before we even see this result. + */ + if (__mnt_is_readonly(nd.mnt)) res = -EROFS; out_path_release: _