hi,
 I use yaffs(the latest cvs from aleph1) on linux-2.4.21 with backported 
 mtd(mtd20040705).there is no problem on the first mount.but it seems 
 like lost data when i umount it then remount it.here is my log:
 1)reset and system run
 2)flash_eraseall /dev/mtd/0 &&insmod yaffs.o
 3)mount -t yaffs /dev/mtdblock/0 ./yaffs_mnt
 4)/yaffs/yaffs_mnt # cp /home/www/rtc_ds1337.o ./
 5)/yaffs/yaffs_mnt # ls -l
 drw-rw-rw-    1 root     root          512 Jan  1 04:23 lost+found
 -rw-r--r--    1 root     root        10745 Jan  1 04:22 rtc_ds1337.o
 6)/yaffs/yaffs_mnt # insmod rtc_ds1337.o
 Using rtc_ds1337.o
 7)/yaffs # umount yaffs_mnt/
 mtdblock_release
 ok
 8)/yaffs # mount -t yaffs /dev/mtdblock/0 ./yaffs_mnt/
 mtdblock_open
 ok
 yaffs: Attempting MTD mount on 31.0, "1f:00"
 9)/yaffs/yaffs_mnt # ls -l
 drw-rw-rw-    1 root     root          512 Jan  1 04:23 lost+found
 -rw-r--r--    1 root     root        10745 Jan  1 04:22 rtc_ds1337.o
 ***you will see the file size is the same as 5)
 10)/yaffs/yaffs_mnt # insmod rtc_ds1337.o
 Using rtc_ds1337.o
 pc : [<4014b5b4>]    lr : [<00043888>]    Not tainted
 sp : bfffd768  ip : bfffd7e4  fp : bfffd7e0
 r10: bfffd9f8  r9 : 00000009  r8 : 000a5df8
 r7 : 00000000  r6 : 001b63b8  r5 : 001b6f48  r4 : 001b6c48
 r3 : 00000000  r2 : 00000009  r1 : 000a5df8  r0 : 00000000
 Flags: nzCv  IRQs on  FIQs on  Mode USER_32  Segment user
 Control: C000717F  Table: 05F90000  DAC: 00000015
 Segmentation fault
 
 i have do as this for times ,it has the same result! so i do consider
 it lose data when umount it.any body can give me some hints?
 thanks! 
  
 JianZhang