I have been using Link2SD for few days now (on my Rooted NexusOne) and I simply loves this application. It solves all the issues of low internal memory for the custom applications.
However from time to time, the SD-Ext partition used by Link2SD gets corrupt. Now I’m not very sure whom to blame for this i.e. Android Kernal, Link2SD or anything application which writes files here. But anyway, I found a simple fix for any such problems, and that’s if you get the read-only file system error when installing or updating the SD-Ext in the Link2SD, you can quickly repair this from the ADB Shell. If you have never used this before, here is quick reference and guide:
Once you have this tool. But the phone into recovery mode, and then run the ADB shell from your command prompt:
Once you see the shell prompt, you can check and fix your sd-ext partition by typing following command:
e2fsck -fpDC0 /dev/block/mmcblk0p2
If fixing is successful, re boot back into phone and try using the Link2SD again.
Update: A quick tip on this (based on my personal experience). If you are using Link2SD and your frequently get the file system error on your SD-Ext partition, then one trick which worked well for me is to change the SD-Ext partition format from the Ext3 or Ext4 to FAT32. This should get rid of most of the file system errors happen during transfer of files.