[Yaffs] Yaffs2 mount/umount issue

Hi,

I am having issue with yaffs2 file system. Files in yaffs2 flash file
system not retained across mount operations. Here is what I am
noticing.

// erase all flash contents
$ flaserase-all /dev/mtd3
// mount yaffs2 to /flash
$ mount -t yaffs2 /dev/mtdblock3 /flash

// add hello.c to flash filesystem
  $cd /flash
  $ cp /hello.c .
  $ls                       // ls lists both lost_found and hello.c as well.
  $ cd /
// unmount flash file system
  $umount /flash

// remount the flash file system
  $ mount -t yaffs2 /dev/mtdblock3 /flash
  $ls                          // ls lists only "lost+found"

Could you explain what causes this behavior?

Thanks,
-Subba