GFS2: Add some useful messages

The following patch adds a message to indicate when barriers have been
disabled due to a block device which doesn't support them. You could
already tell this via the mount options in /proc/mounts, but all the
other filesystems also log a message at the same time.

Also, the same mechanisms are used to indicate when the lock
demote interface has been used (only ever used for debugging)
which is a request from our support team.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/incore.h

@@ -459,6 +459,7 @@ enum {
 	SDF_SHUTDOWN		= 2,
 	SDF_NOBARRIERS		= 3,
 	SDF_NORECOVERY		= 4,
+	SDF_DEMOTE		= 5,
 };
 
 #define GFS2_FSNAME_LEN		256

fs/gfs2/log.c

@@ -600,6 +600,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
 	if (buffer_eopnotsupp(bh)) {
 		clear_buffer_eopnotsupp(bh);
 		set_buffer_uptodate(bh);
+		fs_info(sdp, "barrier sync failed - disabling barriers\n");
 		set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
 		lock_buffer(bh);
 skip_barrier:

fs/gfs2/super.c

@@ -1334,7 +1334,8 @@ static int gfs2_show_options(struct seq_file *s, struct vfsmount *mnt)
 	}
 	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))
 		seq_printf(s, ",nobarrier");
-
+	if (test_bit(SDF_DEMOTE, &sdp->sd_flags))
+		seq_printf(s, ",demote_interface_used");
 	return 0;
 }
 

fs/gfs2/sys.c

@@ -233,6 +233,8 @@ static ssize_t demote_rq_store(struct gfs2_sbd *sdp, const char *buf, size_t len
 	glops = gfs2_glops_list[gltype];
 	if (glops == NULL)
 		return -EINVAL;
+	if (test_and_set_bit(SDF_DEMOTE, &sdp->sd_flags))
+		fs_info(sdp, "demote interface used\n");
 	rv = gfs2_glock_get(sdp, glnum, glops, 0, &gl);
 	if (rv)
 		return rv;