I am using YAFFS2 from the 2.6.32 kernel on an integrated NAND flash device (running android 2.2.1_r1, if that matters).
I am seeing 2 odd things, seems like they are related:
1. There are duplicate entries of the same directory (/data/system, below) when I do ls:
bash-3.2# mount
rootfs on / type rootfs (rw)
/dev/root on / type yaffs2 (rw,relatime)
tmpfs on /dev type tmpfs (rw,relatime,mode=755)
devpts on /dev/pts type devpts (rw,relatime,mode=600)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
tmpfs on /mnt/asec type tmpfs (rw,relatime,mode=755,gid=1000)
tmpfs on /mnt/tmpfs type tmpfs (rw,relatime,size=194144k,mode=777,gid=1000)
/dev/block/mtdblock7 on /data type yaffs2 (rw,nosuid,nodev,relatime)
/dev/block/mtdblock8 on /cache type yaffs2 (rw,nosuid,nodev,relatime)
bash-3.2# ls -ailp /data
1 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 ./
1 drwxrwxr-x 1 0 0 2048 Apr 13 13:50 ../
511 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app/
510 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app-private/
441 drwx------ 1 1000 1000 2048 Jan 1 2000 backup/
264 drwxrwx--x 1 1000 1000 2048 Jul 29 2009 dalvik-cache/
509 drwxrwx--x 1 1000 1000 2048 Apr 13 16:47 data/
265 drwxr-x--- 1 0 1007 2048 Jan 1 2000 dontpanic/
497 drwxrwxrwx 1 1000 1000 2048 Apr 13 16:39 energyhub/
507 drwxrwx--x 1 2000 2000 2048 Jan 1 2000 local/
2 drwxrwx--- 1 0 0 2048 Jan 1 2000 lost+found/
499 drwxrwx--t 1 1000 9998 2048 Jan 1 2000 misc/
256 drwx------ 1 0 0 2048 Apr 13 16:38 property/
498 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:47 system/
498 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:47 system/
2. My duplicate /data/system inode entry keeps swapping between 506 and 498 when I reboot the device:
bash-3.2# date; ls -ailp /data
Wed Apr 13 16:46:32 UTC 2011
1 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 .
1 drwxrwxr-x 1 0 0 2048 Apr 13 13:50 ..
511 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app
510 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app-private
441 drwx------ 1 1000 1000 2048 Jan 1 2000 backup
264 drwxrwx--x 1 1000 1000 2048 Jul 29 2009 dalvik-cache
509 drwxrwx--x 1 1000 1000 2048 Apr 13 16:46 data
265 drwxr-x--- 1 0 1007 2048 Jan 1 2000 dontpanic
497 drwxrwxrwx 1 1000 1000 2048 Apr 13 16:39 energyhub
507 drwxrwx--x 1 2000 2000 2048 Jan 1 2000 local
2 drwxrwx--- 1 0 0 2048 Jan 1 2000 lost+found
499 drwxrwx--t 1 1000 9998 2048 Jan 1 2000 misc
256 drwx------ 1 0 0 2048 Apr 13 16:38 property
506 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:46 system
506 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:46 system
...
<reboot>
Linux version 2.6.32 (mark@eddie) (gcc version 4.3.3 (GCC) ) #2 Wed Mar 30 18:44:20 EDT 2011
...
bash-3.2# date; ls -ailp /data
Wed Apr 13 16:47:11 UTC 2011
1 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 .
1 drwxrwxr-x 1 0 0 2048 Apr 13 13:50 ..
511 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app
510 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app-private
441 drwx------ 1 1000 1000 2048 Jan 1 2000 backup
264 drwxrwx--x 1 1000 1000 2048 Jul 29 2009 dalvik-cache
509 drwxrwx--x 1 1000 1000 2048 Apr 13 16:46 data
265 drwxr-x--- 1 0 1007 2048 Jan 1 2000 dontpanic
497 drwxrwxrwx 1 1000 1000 2048 Apr 13 16:39 energyhub
507 drwxrwx--x 1 2000 2000 2048 Jan 1 2000 local
2 drwxrwx--- 1 0 0 2048 Jan 1 2000 lost+found
499 drwxrwx--t 1 1000 9998 2048 Jan 1 2000 misc
256 drwx------ 1 0 0 2048 Apr 13 16:38 property
498 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:45 system
498 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:45 system
...
<reboot>
...
bash-3.2# date; ls -ailp /data
Wed Apr 13 16:55:26 UTC 2011
1 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 ./
1 drwxrwxr-x 1 0 0 2048 Apr 13 13:50 ../
511 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app/
510 drwxrwx--x 1 1000 1000 2048 Jan 1 2000 app-private/
441 drwx------ 1 1000 1000 2048 Jan 1 2000 backup/
264 drwxrwx--x 1 1000 1000 2048 Jul 29 2009 dalvik-cache/
509 drwxrwx--x 1 1000 1000 2048 Apr 13 16:47 data/
265 drwxr-x--- 1 0 1007 2048 Jan 1 2000 dontpanic/
497 drwxrwxrwx 1 1000 1000 2048 Apr 13 16:39 energyhub/
507 drwxrwx--x 1 2000 2000 2048 Jan 1 2000 local/
2 drwxrwx--- 1 0 0 2048 Jan 1 2000 lost+found/
499 drwxrwx--t 1 1000 9998 2048 Jan 1 2000 misc/
256 drwx------ 1 0 0 2048 Apr 13 16:38 property/
506 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:46 system/
506 drwxrwxr-x 1 1000 1000 2048 Apr 13 16:46 system/
...and so on. And yes, the timestamp did go back in time for the 498 inode version. The device has a battery-backed clock.