On Wednesday 29 August 2012 04:47:19 Jeffrey Johnston wrote:
> I have a client that is currently using a version of YAFFS from about mid
> 2007. They would like to upgrade to the latest version of YAFFS.
> All of their equipment in the field typically gets its load updated every
> year with about 10 to 100 Meg of database stored in the filesystem. I
> have tested upgrading the file system from the old Yaffs to the latest
> YAFFS and have not seen any problems.
> Are there any pitfalls to upgrading the filesystem in the field (with
> existing contents) that I should be aware of?
> I have already verified that downgrades will not work.
> Jeff Johnston

Upgrades should just work.

Downgrades should also work if you disable a few things. The older code does
not have support for block summaries for instance. Checkpoints are visioned
and should be handled properly (ie. non-,atching versions are ignored).

What did you find that did not work in the downgrade?

During the downgrade YAFFS would issue a message complaining about a Partially written block being detected and marking it for retirement. The message was issued from yaffs_ScanBackwards. The checkpoint data was always invalidated because the YAFFS_CHECKPOINT_VERSION changed from 3 to 4.
I did not determine why the sequence number did not match the block that was the current allocation block.
Jeff Johnston