[Cluster-devel] [GFS2 PATCH] GFS2: Reduce number of log flushes

[Bob Peterson <rpeterso@redhat.com>]

Hi,

This patch reduces the number of log flushes.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso@redhat.com> 
---
diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 4bdcf37..7d795e7 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -118,7 +118,13 @@ void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
 		return;
 	__gfs2_ail_flush(gl, fsync);
 	gfs2_trans_end(sdp);
-	gfs2_log_flush(sdp, NULL);
+	/* if fsync is true, we were called from gfs2_fsync, which means
+	   we just called sync_inode_metadata, which calls sync_inode,
+	   which calls writeback_single_inode, which calls write_inode,
+	   which calls write_inode which calls gfs2_log_flush. So the call
+	   is redundant. */
+	if (!fsync)
+		gfs2_log_flush(sdp, NULL);
 }
 
 /**
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 3cbac68..5904ce0 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -1542,7 +1542,11 @@ static void gfs2_evict_inode(struct inode *inode)
 	goto out_unlock;
 
 out_truncate:
-	gfs2_log_flush(sdp, ip->i_gl);
+	/* write_inode_now calls writeback_single_inode, which calls
+	   gfs2_write_inode. gfs2_write_inode calls gfs2_log_flush if
+	   (wbc->sync_mode == WB_SYNC_ALL), which it is since we pass 1.
+	   therefore, this call to gfs2_log_flush is redundant:
+	   gfs2_log_flush(sdp, ip->i_gl); */
 	write_inode_now(inode, 1);
 	gfs2_ail_flush(ip->i_gl, 0);