Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762223AbXKAXPr (ORCPT ); Thu, 1 Nov 2007 19:15:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759594AbXKAXJA (ORCPT ); Thu, 1 Nov 2007 19:09:00 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:49692 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759216AbXKAXI6 (ORCPT ); Thu, 1 Nov 2007 19:08:58 -0400 Subject: [PATCH 21/27] r-o-bind-mounts-make-access-use-mnt-check To: akpm@osdl.org Cc: linux-kernel@vger.kernel.org, miklos@szeredi.hu, hch@infradead.org, Dave Hansen From: Dave Hansen Date: Thu, 01 Nov 2007 16:08:54 -0700 References: <20071101230826.9A4F6E00@kernel> In-Reply-To: <20071101230826.9A4F6E00@kernel> Message-Id: <20071101230854.14E2845F@kernel> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1645 Lines: 44 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 Signed-off-by: Andrew Morton --- linux-2.6.git-dave/fs/open.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff -puN fs/open.c~r-o-bind-mounts-make-access-use-mnt-check fs/open.c --- linux-2.6.git/fs/open.c~r-o-bind-mounts-make-access-use-mnt-check 2007-11-01 14:46:18.000000000 -0700 +++ linux-2.6.git-dave/fs/open.c 2007-11-01 14:46:18.000000000 -0700 @@ -459,8 +459,17 @@ 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: _ - 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/