xfs: Rename xa_ elements to ail_

This is a simple rename, except that xa_ail becomes ail_head.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 3e5ba1e..2f529fd 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1149,7 +1149,7 @@ xlog_assign_tail_lsn_locked(
 	struct xfs_log_item	*lip;
 	xfs_lsn_t		tail_lsn;
 
-	assert_spin_locked(&mp->m_ail->xa_lock);
+	assert_spin_locked(&mp->m_ail->ail_lock);
 
 	/*
 	 * To make sure we always have a valid LSN for the log tail we keep
@@ -1172,9 +1172,9 @@ xlog_assign_tail_lsn(
 {
 	xfs_lsn_t		tail_lsn;
 
-	spin_lock(&mp->m_ail->xa_lock);
+	spin_lock(&mp->m_ail->ail_lock);
 	tail_lsn = xlog_assign_tail_lsn_locked(mp);
-	spin_unlock(&mp->m_ail->xa_lock);
+	spin_unlock(&mp->m_ail->ail_lock);
 
 	return tail_lsn;
 }