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authorSachin Prabhu <sprabhu@redhat.com>2011-08-01 12:10:12 +0100
committerTrond Myklebust <Trond.Myklebust@netapp.com>2011-09-13 17:10:15 -0400
commitfb2088ccc139ffbf1cf359216883712dab4ae43d (patch)
tree88fd8cad42bd9d7518fdc25b519965b37cdcb4a5 /fs/nfs/super.c
parentf13c3620a4d1123dbf032f93f350b856ef292ced (diff)
downloadlwn-fb2088ccc139ffbf1cf359216883712dab4ae43d.tar.gz
lwn-fb2088ccc139ffbf1cf359216883712dab4ae43d.zip
nfs: Do not allow multiple mounts on same mountpoint when using -o noac
Do not allow multiple mounts on same mountpoint when using -o noac 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. The patch checks for noac and assigns the sync flag before sget() is called to obtain an already existing superblock structure. Signed-off-by: Sachin Prabhu <sprabhu@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'fs/nfs/super.c')
-rw-r--r--fs/nfs/super.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index b961ceac66b4..9b7dd7013b15 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2035,9 +2035,6 @@ static inline void nfs_initialise_sb(struct super_block *sb)
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);
@@ -2249,6 +2246,10 @@ static struct dentry *nfs_fs_mount(struct file_system_type *fs_type,
if (server->flags & NFS_MOUNT_UNSHARED)
compare_super = NULL;
+ /* -o noac implies -o sync */
+ 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)) {
@@ -2361,6 +2362,10 @@ nfs_xdev_mount(struct file_system_type *fs_type, int flags,
if (server->flags & NFS_MOUNT_UNSHARED)
compare_super = NULL;
+ /* -o noac implies -o sync */
+ 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)) {
@@ -2628,6 +2633,10 @@ nfs4_remote_mount(struct file_system_type *fs_type, int flags,
if (server->flags & NFS4_MOUNT_UNSHARED)
compare_super = NULL;
+ /* -o noac implies -o sync */
+ 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)) {
@@ -2916,6 +2925,10 @@ nfs4_xdev_mount(struct file_system_type *fs_type, int flags,
if (server->flags & NFS4_MOUNT_UNSHARED)
compare_super = NULL;
+ /* -o noac implies -o sync */
+ 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)) {
@@ -3003,6 +3016,10 @@ nfs4_remote_referral_mount(struct file_system_type *fs_type, int flags,
if (server->flags & NFS4_MOUNT_UNSHARED)
compare_super = NULL;
+ /* -o noac implies -o sync */
+ 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)) {