ext4: correctly report "not supported" for {usr,grp}jquota when !CONFIG_QUOTA

The macro MOPT_Q is used to indicates the mount option is related to
quota stuff and is defined to be MOPT_NOSUPPORT when CONFIG_QUOTA is
disabled.  Normally the quota options are handled explicitly, so it
didn't matter that the MOPT_STRING flag was missing, even though the
usrjquota and grpjquota mount options take a string argument.  It's
important that's present in the !CONFIG_QUOTA case, since without
MOPT_STRING, the mount option matcher will match usrjquota= followed
by an integer, and will otherwise skip the table entry, and so "mount
option not supported" error message is never reported.

[ Fixed up the commit description to better explain why the fix
  works. --TYT ]

Fixes: 26092bf5 ("ext4: use a table-driven handler for mount options")
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Link: https://lore.kernel.org/r/1603986396-28917-1-git-send-email-kaixuxia@tencent.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

fs/ext4/super.c

@@ -2027,8 +2027,8 @@ static const struct mount_opts {
 	{Opt_noquota, (EXT4_MOUNT_QUOTA | EXT4_MOUNT_USRQUOTA |
 		       EXT4_MOUNT_GRPQUOTA | EXT4_MOUNT_PRJQUOTA),
 							MOPT_CLEAR | MOPT_Q},
-	{Opt_usrjquota, 0, MOPT_Q},
-	{Opt_grpjquota, 0, MOPT_Q},
+	{Opt_usrjquota, 0, MOPT_Q | MOPT_STRING},
+	{Opt_grpjquota, 0, MOPT_Q | MOPT_STRING},
 	{Opt_offusrjquota, 0, MOPT_Q},
 	{Opt_offgrpjquota, 0, MOPT_Q},
 	{Opt_jqfmt_vfsold, QFMT_VFS_OLD, MOPT_QFMT},