Re: Help - how to identify the callers in a SCSI lower-leveldriver

[Abhishek Rai <abba@cs.sunysb.edu>]

> > The shim (a pseudo SCSI lower-level driver) we are working on sits in
> > between Linux SCSI mid-level driver and our existing kernel driver which
> > interfaces with a FC driver which interacts with the FC HBA.
>
> wow that sounds like a great way to kill performance, that many extra layers
>
> >
> > To track SCSI initiators' tasks, it would be great if our existing kernel
> > driver knows which application makes the (SCSI passthrough ioctl) call to
> > /dev/sda.
>
> well... it's a fundamentally hard problem. For example the application that
> submitted the IO may no longer exist on disk by the time you get to see the
> IO, or the process may already have exited. It sounds like a fundamentally
> fragile/broken concept to use this information for *anything*, it's still
> not clear to me what you'd use it for (other than doing a gross hack by
> faking IO priorities based on application name but that's sooo not the right
> solution to that problem)
>

If it is just a feature you want in your development driver, you can do it
at the file system level, e.g., modify an existing file system, or better
still, have a thin stackable file system layer that does that. Then you
can mount the file system on your /dev/sda so that the stackable file
system sits in between the underlying file system and the VFS.

Abhishek