1 files changed, 31 insertions, 13 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index ad0c69ee8947..fa2d05e65ff1 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1475,14 +1475,14 @@ xlog_commit_record(
 }
 
 /*
- * Push on the buffer cache code if we ever use more than 75% of the on-disk
- * log space.  This code pushes on the lsn which would supposedly free up
- * the 25% which we want to leave free.  We may need to adopt a policy which
- * pushes on an lsn which is further along in the log once we reach the high
- * water mark.  In this manner, we would be creating a low water mark.
+ * Compute the LSN that we'd need to push the log tail towards in order to have
+ * (a) enough on-disk log space to log the number of bytes specified, (b) at
+ * least 25% of the log space free, and (c) at least 256 blocks free.  If the
+ * log free space already meets all three thresholds, this function returns
+ * NULLCOMMITLSN.
  */
-STATIC void
-xlog_grant_push_ail(
+xfs_lsn_t
+xlog_grant_push_threshold(
 	struct xlog	*log,
 	int		need_bytes)
 {
@@ -1508,7 +1508,7 @@ xlog_grant_push_ail(
 	free_threshold = max(free_threshold, (log->l_logBBsize >> 2));
 	free_threshold = max(free_threshold, 256);
 	if (free_blocks >= free_threshold)
-		return;
+		return NULLCOMMITLSN;
 
 	xlog_crack_atomic_lsn(&log->l_tail_lsn, &threshold_cycle,
 						&threshold_block);
@@ -1528,13 +1528,33 @@ xlog_grant_push_ail(
 	if (XFS_LSN_CMP(threshold_lsn, last_sync_lsn) > 0)
 		threshold_lsn = last_sync_lsn;
 
+	return threshold_lsn;
+}
+
+/*
+ * Push the tail of the log if we need to do so to maintain the free log space
+ * thresholds set out by xlog_grant_push_threshold.  We may need to adopt a
+ * policy which pushes on an lsn which is further along in the log once we
+ * reach the high water mark.  In this manner, we would be creating a low water
+ * mark.
+ */
+STATIC void
+xlog_grant_push_ail(
+	struct xlog	*log,
+	int		need_bytes)
+{
+	xfs_lsn_t	threshold_lsn;
+
+	threshold_lsn = xlog_grant_push_threshold(log, need_bytes);
+	if (threshold_lsn == NULLCOMMITLSN || XLOG_FORCED_SHUTDOWN(log))
+		return;
+
 	/*
 	 * Get the transaction layer to kick the dirty buffers out to
 	 * disk asynchronously. No point in trying to do this if
 	 * the filesystem is shutting down.
 	 */
-	if (!XLOG_FORCED_SHUTDOWN(log))
-		xfs_ail_push(log->l_ailp, threshold_lsn);
+	xfs_ail_push(log->l_ailp, threshold_lsn);
 }
 
 /*
@@ -1604,9 +1624,7 @@ xlog_cksum(
 		int		i;
 		int		xheads;
 
-		xheads = size / XLOG_HEADER_CYCLE_SIZE;
-		if (size % XLOG_HEADER_CYCLE_SIZE)
-			xheads++;
+		xheads = DIV_ROUND_UP(size, XLOG_HEADER_CYCLE_SIZE);
 
 		for (i = 1; i < xheads; i++) {
 			crc = crc32c(crc, &xhdr[i].hic_xheader,