[Stgt-devel] Dealing with filemarks in SSC ...

[Richard Sharpe]

Hi,

I have moved closer to properly implementing filemarks (and setmarks)
by thinking through the issues associated with the approach I want to
take.

That is to keep an array of marks (file and set) with offsets into the
backing store file. Whether these are then stored as extended
attributes or as a separate metadata file is an implementation
decision that I am happy with either way.

By the look of things, the cost of detecting a mark on each read op,
at least for fixed block size devices, is a couple of additions and a
comparison in the fast-path (although the code does lots of seeks that
seem unnecessary at the moment as well). I suspect it will amount to
the same for variable block-size devices as well.

Once I have btape tests working correctly I will post a patch for consideration.