xfs: factor out forced iclog flushes

We force iclogs in several places - we need them all to have the
same cache flush semantics, so start by factoring out the iclog
force into a common helper.
Signed-off-by: Dave Chinner <dchinner@redhat.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

@@ -778,6 +778,20 @@ xfs_log_mount_cancel(
 	xfs_log_unmount(mp);
 }
 
+/*
+ * Flush out the iclog to disk ensuring that device caches are flushed and
+ * the iclog hits stable storage before any completion waiters are woken.
+ */
+static inline int
+xlog_force_iclog(
+	struct xlog_in_core	*iclog)
+{
+	atomic_inc(&iclog->ic_refcnt);
+	if (iclog->ic_state == XLOG_STATE_ACTIVE)
+		xlog_state_switch_iclogs(iclog->ic_log, iclog, 0);
+	return xlog_state_release_iclog(iclog->ic_log, iclog, 0);
+}
+
 /*
  * Wait for the iclog and all prior iclogs to be written disk as required by the
  * log force state machine. Waiting on ic_force_wait ensures iclog completions
@@ -863,18 +877,8 @@ xlog_unmount_write(
 
 	spin_lock(&log->l_icloglock);
 	iclog = log->l_iclog;
-	atomic_inc(&iclog->ic_refcnt);
-	if (iclog->ic_state == XLOG_STATE_ACTIVE)
-		xlog_state_switch_iclogs(log, iclog, 0);
-	else
-		ASSERT(iclog->ic_state == XLOG_STATE_WANT_SYNC ||
-		       iclog->ic_state == XLOG_STATE_IOERROR);
-	/*
-	 * Ensure the journal is fully flushed and on stable storage once the
-	 * iclog containing the unmount record is written.
-	 */
 	iclog->ic_flags |= (XLOG_ICL_NEED_FLUSH | XLOG_ICL_NEED_FUA);
-	error = xlog_state_release_iclog(log, iclog, 0);
+	error = xlog_force_iclog(iclog);
 	xlog_wait_on_iclog(iclog);
 
 	if (tic) {
@@ -3201,17 +3205,9 @@ xfs_log_force(
 		iclog = iclog->ic_prev;
 	} else if (iclog->ic_state == XLOG_STATE_ACTIVE) {
 		if (atomic_read(&iclog->ic_refcnt) == 0) {
-			/*
-			 * We are the only one with access to this iclog.
-			 *
-			 * Flush it out now.  There should be a roundoff of zero
-			 * to show that someone has already taken care of the
-			 * roundoff from the previous sync.
-			 */
-			atomic_inc(&iclog->ic_refcnt);
+			/* We have exclusive access to this iclog. */
 			lsn = be64_to_cpu(iclog->ic_header.h_lsn);
-			xlog_state_switch_iclogs(log, iclog, 0);
-			if (xlog_state_release_iclog(log, iclog, 0))
+			if (xlog_force_iclog(iclog))
 				goto out_error;
 
 			if (be64_to_cpu(iclog->ic_header.h_lsn) != lsn)
@@ -3289,9 +3285,7 @@ xlog_force_lsn(
 					&log->l_icloglock);
 			return -EAGAIN;
 		}
-		atomic_inc(&iclog->ic_refcnt);
-		xlog_state_switch_iclogs(log, iclog, 0);
-		if (xlog_state_release_iclog(log, iclog, 0))
+		if (xlog_force_iclog(iclog))
 			goto out_error;
 		if (log_flushed)
 			*log_flushed = 1;