Fixed using CF-Root's CWM4 kernel (a kernel with a patched pm2.c, thanks to ilarrain) and add 2 lines command to init.rc to load jbd2 and ext4 modules.

For CyanogenMod 7.1 and advance user only for now!

How to flash:
- Boot your device into CWM recovery
- Push recovery-clockwork-5.0.2.3-galaxyace.img to your device using "adb push recovery-clockwork-5.0.2.3-galaxyace.img /tmp/" command
- Login to your device over "adb shell"
- Mount /system using "mount /dev/block/stl12 /system" command
- Flash CWM recovery using "flash_image recoveryonly /tmp/recovery-clockwork-5.0.2.3-galaxyace.img" command
- Umount /system using "umount /system" command
- Reboot your device using "reboot recovery" command to test your new CWM recovery
- Reboot your device

Not fully tested and have no enough space to try the backup/restore function

EDIT:
Recovery flashable zip added.

EDIT2:
Please try the *-fix.zip version.
Changelog:
- mount, umount, and rm scripts taken from my CF-Root-S5830 CWM to fix mount error problem
- /etc/recovery.fstab changed to mount /sd-ext partition and to fix recovery backup problem

EmoBoiix3 and Lovetz, waiting for your report

EDIT3:
The fix version almost same as clockwork-5.0.2.6 I have modified before and shared here by Grif_05, except:
- remove a garbage file
- ext4 support compiled in kernel, not as a module
- using new Samsung proprietary modules taken from DXKPD
Attached Files
File Type: zip recovery-clockwork-5.0.2.6-galaxyace-fix.zip - [Click for QR Code] (5.42 MB, 970239 views)