xfs: dont set sb in xfs_mount_alloc()

When changing to use the new mount api the super block won't be
available when the xfs_mount struct is allocated so move setting the
super block in xfs_mount to xfs_fs_fill_super().
Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_super.c

@@ -1560,8 +1560,7 @@ xfs_destroy_percpu_counters(
 }
 
 static struct xfs_mount *
-xfs_mount_alloc(
-	struct super_block	*sb)
+xfs_mount_alloc(void)
 {
 	struct xfs_mount	*mp;
 
@@ -1569,7 +1568,6 @@ xfs_mount_alloc(
 	if (!mp)
 		return NULL;
 
-	mp->m_super = sb;
 	spin_lock_init(&mp->m_sb_lock);
 	spin_lock_init(&mp->m_agirotor_lock);
 	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
@@ -1605,9 +1603,10 @@ xfs_fs_fill_super(
 	 * allocate mp and do all low-level struct initializations before we
 	 * attach it to the super
 	 */
-	mp = xfs_mount_alloc(sb);
+	mp = xfs_mount_alloc();
 	if (!mp)
 		goto out;
+	mp->m_super = sb;
 	sb->s_fs_info = mp;
 
 	error = xfs_parseargs(mp, (char *)data);