xfs: lift writable fs check up into log worker task

The log covering helper checks whether the filesystem is writable to
determine whether to cover the log. The helper is currently only
called from the background log worker. In preparation to reuse the
helper from freezing contexts, lift the check into xfs_log_worker().
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/xfs_log.c

@@ -1051,14 +1051,12 @@ xfs_log_space_wake(
  * there's no point in running a dummy transaction at this point because we
  * can't start trying to idle the log until both the CIL and AIL are empty.
  */
-static int
-xfs_log_need_covered(xfs_mount_t *mp)
+static bool
+xfs_log_need_covered(
+	struct xfs_mount	*mp)
 {
-	struct xlog	*log = mp->m_log;
-	int		needed = 0;
-
-	if (!xfs_fs_writable(mp, SB_FREEZE_WRITE))
-		return 0;
+	struct xlog		*log = mp->m_log;
+	bool			needed = false;
 
 	if (!xlog_cil_empty(log))
 		return 0;
@@ -1076,14 +1074,14 @@ xfs_log_need_covered(xfs_mount_t *mp)
 		if (!xlog_iclogs_empty(log))
 			break;
 
-		needed = 1;
+		needed = true;
 		if (log->l_covered_state == XLOG_STATE_COVER_NEED)
 			log->l_covered_state = XLOG_STATE_COVER_DONE;
 		else
 			log->l_covered_state = XLOG_STATE_COVER_DONE2;
 		break;
 	default:
-		needed = 1;
+		needed = true;
 		break;
 	}
 	spin_unlock(&log->l_icloglock);
@@ -1273,7 +1271,7 @@ xfs_log_worker(
 	struct xfs_mount	*mp = log->l_mp;
 
 	/* dgc: errors ignored - not fatal and nowhere to report them */
-	if (xfs_log_need_covered(mp)) {
+	if (xfs_fs_writable(mp, SB_FREEZE_WRITE) && xfs_log_need_covered(mp)) {
 		/*
 		 * Dump a transaction into the log that contains no real change.
 		 * This is needed to stamp the current tail LSN into the log