I just recently starting having an issue with the Notes application corrupting files on my N810's internal 2GB card.

I can vi /media/mmc2/tmp/foo.txt, then make and save changes, and cat the same file all from the CLI. I can then open foo.txt inside the Notes app, view the edits, do not make any changes and close Notes. No issues. However if I make any edits to foo.txt within Notes app, then save, the file is somehow corrupted. I can not reopen it in Notes (shows a blank document).
cat /media/mmc2/tmp/foo.txt
gives error message:
cat: read error: Input/output error

Any suggestions of what I should look for to troubleshoot?
Is the mmc2 a FAT volume? (it's not listed in /etc/fstab) I ask because I can't run chown or chmod on files in mmc2.

I believe it is (vfat)

Yes, it is FAT. I'd suggest you plug your n810 into a PC and then run chkdsk on the drives. I've had to do this a few times: /media/mmc2 does seem to get corrupted rather easily.

If you have a swapfile on this drive then you might want to turn it off first: I'm not sure but I suspect mounting the drive on a PC while the swapfile is enabled may be part of the problem.

It's definitely vfat. Some N810 had wrongly formatted internal memory cards (formatted for slightly larger than the physical size of the medium). As soon as Linux detects that (when it tries to write past the end of the medium), it should put the filesystem into Read-Only mode to avoid corruption. However, maybe in your case it didn't detect it but is still corrupting it? Try reformatting the card, which should solve the wrong-formatting issue.

Duncan:
The Nokia will automatically turn off swap when the drive is being mounted on the PC. If that is not possible (too much RAM being used), it will refuse to be mounted (and an error message to that effect will be displayed).

Excellent suggestions everyone, thank you. I'll try this out tonight when I'm near my PC with the USB cable.

FWIW, I normally have to power cycle the N810 before plugging in the USB cable because I'm using swap space on /media/mmc2 and it's in use according to "load-applet" showing a floppy disk icon in the memory usage bar graph.

When I plugged the USB cable in the last time I got the typical error message about not being able to use the memory card, so I closed all open apps to see if that would close up the swap space. Nope, just one bar with a floppy icon which I assume means swap file is still in use. I figured what the heck, try the USB connection again and this time it mounted without any error message. I get the impression that this is a VERY BAD IDEA from your messages.

Also FWIW, I've been having fun attempting to get videos running on the N810 and I've been filling my 2GB internal card quite a bit. df -h shows 289MB free space right now on mmc2, so I may not be getting to an incorrectly reported limit, but I'd imagine there also could be some fragmentation issues. A reformat also sounds like a very good idea. Is there a preferred formating tool that I should use? Feel free to suggest CLI tools too.

Update:
chkdsk would abort during its run, but did create folder called FOUND, so it was finding issues.

Used robocopy to backup as much as possible off mmc2 to my PC. Only a few files were corrupted and could not be read. The NoteCase auto-create-backup-files option saved my butt big time in this situation for my encrypted DB. The backup files all work and are readable on my PC.

Searched to find the best way to format mmc2 from the tablet CLI and found out that the issue I'm having has nothing to do with Notes app. m_stolle was exactly correct in their assessment of my issue.

Newbie ALERT! There is an issue with N810's internal 2GB flash memory. If you don't have corruption now, you may get it soon. Bug report is here. My allocated block size was the incorrect "1999206" as shown in the bug report.

Fix was done by following this post.

If I do a newbie perspective write-up of how to fix this issue, could the post be made into a stickie for the newbie group? (not a lot of stickies here and instead a lot of "use the search" messages ) I could have avoided getting corrupted files if I fixed this when I first got the N810 and I'd like to save others of the same or worse pain.

Ok, so not the swapfile after all. I guess I'm going to have to repartition that drive.

Speednut, couldn't you just reformat the internal 2GB from the file manager?

That would be a lot easier for newbies to cope with than command line stuff.