This is a bug to cover the activity of adding tracepoints to the GFS2 filesystem. Such things will be very useful for both functional test/debugging and performance analysis.

Originally I wrote an extension for blktrace to track glocks and block I/O via the same mechanism. This has already proved itself useful in solving a bug. I've received a suggestion that we should be using the generic tracepoints code rather than trying to tack onto blktrace. That will be ok provided we can maintain relative ordering between glocks and block I/O and provided that no extra overhead is introduced.

In addition there are other places in which we could usefully add tracepoints. Currently those include:

 1. Journalling (tracking blocks going in/out of the journal & writeback)
 2. Block allocation/deallocation

Tracepoints are undergoing rapid development at the moment. It may be wise to wait until after the next merge window in order to continue this development so that the core code has stabilised a bit.