gfs2: Fix initialisation of args for remount

When gfs2 was converted to use fs_context, the initialisation of the
mount args structure to the currently active args was lost with the
removal of gfs2_remount_fs(), so the checks of the new args on remount
became checks against the default values instead of the current ones.
This caused unexpected remount behaviour and test failures (xfstests
generic/294, generic/306 and generic/452).

Reinstate the args initialisation, this time in gfs2_init_fs_context()
and conditional upon fc->purpose, as that's the only time we get control
before the mount args are parsed in the remount process.

Fixes: 1f52aa08 ("gfs2: Convert gfs2 to fs_context")
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/ops_fstype.c

@@ -1540,17 +1540,23 @@ static int gfs2_init_fs_context(struct fs_context *fc)
 {
 	struct gfs2_args *args;
 
-	args = kzalloc(sizeof(*args), GFP_KERNEL);
+	args = kmalloc(sizeof(*args), GFP_KERNEL);
 	if (args == NULL)
 		return -ENOMEM;
 
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
+		struct gfs2_sbd *sdp = fc->root->d_sb->s_fs_info;
+
+		*args = sdp->sd_args;
+	} else {
+		memset(args, 0, sizeof(*args));
 		args->ar_quota = GFS2_QUOTA_DEFAULT;
 		args->ar_data = GFS2_DATA_DEFAULT;
 		args->ar_commit = 30;
 		args->ar_statfs_quantum = 30;
 		args->ar_quota_quantum = 60;
 		args->ar_errors = GFS2_ERRORS_DEFAULT;
-
+	}
 	fc->fs_private = args;
 	fc->ops = &gfs2_context_ops;
 	return 0;