gfs2: Convert gfs2 to fs_context

Convert gfs2 and gfs2meta to fs_context. Removes the duplicated vfs code
from gfs2_mount and instead uses the new vfs_get_block_super() before
switching the ->root to the appropriate dentry.

The mount option parsing has been converted to the new API and error
reporting for invalid options has been made more precise at the same
time.

All of the mount/remount code has been moved into ops_fstype.c

Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: cluster-devel@redhat.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/gfs2/incore.h

@@ -584,10 +584,10 @@ struct gfs2_args {
 	unsigned int ar_rgrplvb:1;		/* use lvbs for rgrp info */
 	unsigned int ar_loccookie:1;		/* use location based readdir
 						   cookies */
-	int ar_commit;				/* Commit interval */
-	int ar_statfs_quantum;			/* The fast statfs interval */
-	int ar_quota_quantum;			/* The quota interval */
-	int ar_statfs_percent;			/* The % change to force sync */
+	s32 ar_commit;				/* Commit interval */
+	s32 ar_statfs_quantum;			/* The fast statfs interval */
+	s32 ar_quota_quantum;			/* The quota interval */
+	s32 ar_statfs_percent;			/* The % change to force sync */
 };
 
 struct gfs2_tune {