NFS: suppressing showing of default mount port value in /proc fixed

Update: added check for zero value as it was before (note: can't simply check
mountd_port for positive value because it's typeof unsigned short)

Default value for mount server port is set to NFS_UNSPEC_PORT (-1) and will not
be changed during parsing mount options for mound data version 6. This default
value will be showed for mountport in /proc/mounts always since current default
check is for zero value. This small mistake leads to big problem, because
during umount.nfs execution from old user-space utils (at least nfs-utils
1.0.9) this value will be used as the server port to connect to. This request
will be rejected (since port is 65535) and thus nfs mount point can't be
unmounted.

Note from Chuck Lever (chuck.lever@oracle.com): this is only possible if
/etc/mtab is a link to /proc/mounts.  Not all systems have this configuration.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 4100630c9a5b65f47bb5379ee2bc62f78e60284e..dd56eec16eac5e7a095ef36aae0c2117fab1e875 100644 (file)
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -598,7 +598,9 @@ static void nfs_show_mountd_options(struct seq_file *m, struct nfs_server *nfss,
 
        if (nfss->mountd_version || showdefaults)
                seq_printf(m, ",mountvers=%u", nfss->mountd_version);
-       if (nfss->mountd_port || showdefaults)
+       if ((nfss->mountd_port &&
+               nfss->mountd_port != (unsigned short)NFS_UNSPEC_PORT) ||
+               showdefaults)
                seq_printf(m, ",mountport=%u", nfss->mountd_port);
 
        nfs_show_mountd_netid(m, nfss, showdefaults);