3 files changed, 34 insertions, 7 deletions

diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index dab5d38..003e5f2 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -659,9 +659,17 @@ xfs_fs_sync_super(
 	int			error;
 	int			flags;
 
-	if (unlikely(sb->s_frozen == SB_FREEZE_WRITE))
-		flags = SYNC_QUIESCE;
-	else
+	if (unlikely(sb->s_frozen == SB_FREEZE_WRITE)) {
+		/*
+		 * First stage of freeze - no more writers will make progress
+		 * now we are here, so we flush delwri and delalloc buffers
+		 * here, then wait for all I/O to complete.  Data is frozen at
+		 * that point. Metadata is not frozen, transactions can still
+		 * occur here so don't bother flushing the buftarg (i.e
+		 * SYNC_QUIESCE) because it'll just get dirty again.
+		 */
+		flags = SYNC_FSDATA | SYNC_DELWRI | SYNC_WAIT | SYNC_DIO_WAIT;
+	} else
 		flags = SYNC_FSDATA | (wait ? SYNC_WAIT : 0);
 
 	error = bhv_vfs_sync(vfsp, flags, NULL);
diff --git a/fs/xfs/linux-2.6/xfs_vfs.h b/fs/xfs/linux-2.6/xfs_vfs.h
index da255bd..558823a 100644
--- a/fs/xfs/linux-2.6/xfs_vfs.h
+++ b/fs/xfs/linux-2.6/xfs_vfs.h
@@ -92,6 +92,7 @@ typedef enum {
 #define SYNC_REFCACHE		0x0040  /* prune some of the nfs ref cache */
 #define SYNC_REMOUNT		0x0080  /* remount readonly, no dummy LRs */
 #define SYNC_QUIESCE		0x0100  /* quiesce fileystem for a snapshot */
+#define SYNC_DIO_WAIT		0x0200  /* wait for direct I/O to complete */
 
 #define SHUTDOWN_META_IO_ERROR	0x0001	/* write attempt to metadata failed */
 #define SHUTDOWN_LOG_IO_ERROR	0x0002	/* write attempt to the log failed */
diff --git a/fs/xfs/xfs_vfsops.c b/fs/xfs/xfs_vfsops.c
index f5ea74b..c2a6eab 100644
--- a/fs/xfs/xfs_vfsops.c
+++ b/fs/xfs/xfs_vfsops.c
@@ -872,6 +872,10 @@ xfs_statvfs(
  *		       this by simply making sure the log gets flushed
  *		       if SYNC_BDFLUSH is set, and by actually writing it
  *		       out otherwise.
+ *	SYNC_DIO_WAIT - The caller wants us to wait for all direct I/Os
+ *		       as well to ensure all data I/O completes before we
+ *		       return. Forms the drain side of the write barrier needed
+ *		       to safely quiesce the filesystem.
  *
  */
 /*ARGSUSED*/
@@ -883,10 +887,7 @@ xfs_sync(
 {
 	xfs_mount_t	*mp = XFS_BHVTOM(bdp);
 
-	if (unlikely(flags == SYNC_QUIESCE))
-		return xfs_quiesce_fs(mp);
-	else
-		return xfs_syncsub(mp, flags, NULL);
+	return xfs_syncsub(mp, flags, NULL);
 }
 
 /*
@@ -1172,6 +1173,12 @@ xfs_sync_inodes(
 			}
 
 		}
+		/*
+		 * When freezing, we need to wait ensure direct I/O is complete
+		 * as well to ensure all data modification is complete here
+		 */
+		if (flags & SYNC_DIO_WAIT)
+			vn_iowait(vp);
 
 		if (flags & SYNC_BDFLUSH) {
 			if ((flags & SYNC_ATTR) &&
@@ -1950,15 +1957,26 @@ xfs_showargs(
 	return 0;
 }
 
+/*
+ * Second stage of a freeze. The data is already frozen, now we have to take
+ * care of the metadata. New transactions are already blocked, so we need to
+ * wait for any remaining transactions to drain out before proceding.
+ */
 STATIC void
 xfs_freeze(
 	bhv_desc_t	*bdp)
 {
 	xfs_mount_t	*mp = XFS_BHVTOM(bdp);
 
+	/* wait for all modifications to complete */
 	while (atomic_read(&mp->m_active_trans) > 0)
 		delay(100);
 
+	/* flush inodes and push all remaining buffers out to disk */
+	xfs_quiesce_fs(mp);
+
+	BUG_ON(atomic_read(&mp->m_active_trans) > 0);
+
 	/* Push the superblock and write an unmount record */
 	xfs_log_unmount_write(mp);
 	xfs_unmountfs_writesb(mp);