[XFS] Ensure sb not flushed async on a SYNC_WAIT sync. Fixed by Bart Samwel.

SGI Modid: xfs-linux:xfs-kern:169208a

fs/xfs/xfs_vfsops.c

@@ -1487,8 +1487,10 @@ xfs_syncsub(
 			 */
 			if (XFS_BUF_ISPINNED(bp))
 				xfs_log_force(mp, (xfs_lsn_t)0, XFS_LOG_FORCE);
-			if (!(flags & SYNC_WAIT))
-				XFS_BUF_BFLAGS(bp) |= XFS_B_ASYNC;
+			if (flags & SYNC_WAIT)
+				XFS_BUF_UNASYNC(bp);
+			else
+				XFS_BUF_ASYNC(bp);
 			error = xfs_bwrite(mp, bp);
 		}
 		if (error) {