Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758186Ab0DWQin (ORCPT ); Fri, 23 Apr 2010 12:38:43 -0400 Received: from mx3-phx2.redhat.com ([209.132.183.24]:59132 "EHLO mx01.colomx.prod.int.phx2.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758104Ab0DWQij (ORCPT ); Fri, 23 Apr 2010 12:38:39 -0400 Date: Fri, 23 Apr 2010 12:38:38 -0400 (EDT) From: Sachin Prabhu To: linux-kernel Message-ID: <12694330.1491272040714232.JavaMail.sprabhu@sprabhu.fab.redhat.com> In-Reply-To: <21099631.1471272040654142.JavaMail.sprabhu@sprabhu.fab.redhat.com> Subject: A share can be mounted multiple times on the same mountpoint when using the option 'noac' MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.5.5.71] X-Mailer: Zimbra 5.0.21_GA_3150.RHEL4_64 (Zimbra Desktop/1.0.4_1833_Linux) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3932 Lines: 84 When you normally attempt to mount a share twice on the same mountpoint, a check in do_add_mount causes it to return an error # mount localhost:/nfsv3 /mnt # mount localhost:/nfsv3 /mnt mount.nfs: /mnt is already mounted or busy However when using the option 'noac', the user is able to mount the same share on the same mountpoint multiple times. This happens because a share mounted with the noac option is automatically assigned the 'sync' flag MS_SYNCHRONOUS in nfs_initialise_sb(). This flag is set after the check for already existing superblocks is done in sget(). The check for the mount flags in nfs_compare_mount_options() does not take into account the 'sync' flag applied later on in the code path. This means that when using 'noac', a new superblock structure is assigned for every new mount of the same share and multiple shares on the same mountpoint are allowed. ie. # mount -onoac localhost:/nfsv3 /mnt can be run multiple times. Could the existing behavior be considered to be a bug? If yes, one possible fix for this issue is to move the 'sync' flag assignment before the sget() is called to obtain an already existing superblock structure. Signed-off-by: Sachin Prabhu diff -up linux-2.6/fs/nfs/super.c.noac_multiple_mount linux-2.6/fs/nfs/super.c --- linux-2.6/fs/nfs/super.c.noac_multiple_mount 2010-04-22 17:08:25.000000000 +0100 +++ linux-2.6/fs/nfs/super.c 2010-04-22 17:27:48.000000000 +0100 @@ -1992,9 +1992,6 @@ static inline void nfs_initialise_sb(str sb->s_blocksize = nfs_block_bits(server->wsize, &sb->s_blocksize_bits); - if (server->flags & NFS_MOUNT_NOAC) - sb->s_flags |= MS_SYNCHRONOUS; - sb->s_bdi = &server->backing_dev_info; nfs_super_set_maxbytes(sb, server->maxfilesize); @@ -2202,6 +2199,9 @@ static int nfs_get_sb(struct file_system if (server->flags & NFS_MOUNT_UNSHARED) compare_super = NULL; + if (server->flags & NFS_MOUNT_NOAC) + sb_mntdata.mntflags |= MS_SYNCHRONOUS; + /* Get a superblock - note that we may end up sharing one that already exists */ s = sget(fs_type, compare_super, nfs_set_super, &sb_mntdata); if (IS_ERR(s)) { @@ -2317,6 +2317,9 @@ static int nfs_xdev_get_sb(struct file_s if (server->flags & NFS_MOUNT_UNSHARED) compare_super = NULL; + if (server->flags & NFS_MOUNT_NOAC) + sb_mntdata.mntflags |= MS_SYNCHRONOUS; + /* Get a superblock - note that we may end up sharing one that already exists */ s = sget(&nfs_fs_type, compare_super, nfs_set_super, &sb_mntdata); if (IS_ERR(s)) { @@ -2572,6 +2575,9 @@ static int nfs4_remote_get_sb(struct fil if (server->flags & NFS4_MOUNT_UNSHARED) compare_super = NULL; + if (server->flags & NFS_MOUNT_NOAC) + sb_mntdata.mntflags |= MS_SYNCHRONOUS; + /* Get a superblock - note that we may end up sharing one that already exists */ s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata); if (IS_ERR(s)) { @@ -2808,6 +2814,9 @@ static int nfs4_xdev_get_sb(struct file_ if (server->flags & NFS4_MOUNT_UNSHARED) compare_super = NULL; + if (server->flags & NFS_MOUNT_NOAC) + sb_mntdata.mntflags |= MS_SYNCHRONOUS; + /* Get a superblock - note that we may end up sharing one that already exists */ s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata); if (IS_ERR(s)) { @@ -2893,6 +2902,9 @@ static int nfs4_remote_referral_get_sb(s if (server->flags & NFS4_MOUNT_UNSHARED) compare_super = NULL; + if (server->flags & NFS_MOUNT_NOAC) + sb_mntdata.mntflags |= MS_SYNCHRONOUS; + /* Get a superblock - note that we may end up sharing one that already exists */ s = sget(&nfs4_fs_type, compare_super, nfs_set_super, &sb_mntdata); if (IS_ERR(s)) { -- 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/