Commits on May 15, 2023

1. Rewrite SCSI support in new package …

   The existing SCSI implementation in internal/uvm has evolved organically
   over time into what it is today. This creates unecessary difficulty when
   adding new features to the code, makes it harder to maintain, and has
   been a source of bugs.
   
   Additionally, there is a significant functional issue that the current
   scsi code tightly couples the idea of attaching a SCSI device to a VM,
   with the use/mounting of that device inside the VM. This creates
   difficulty when we want to re-use the same SCSI attachment multiple
   times, especially in the future when we will need to mount multiple
   partitions from a device.
   
   This is addressed here by largely rewriting the shim's SCSI code, and
   moving it to a new internal/uvm/scsi package. The new code features a
   main Manager type, which delegates to attachManager and mountManager for
   tracking of attachments to the VM, and mounting of devices inside the
   VM, respectively. attachManager and mountManager also rely on a set of
   interfaces for the actual backend implementation of interacting with a
   VM. This will also allow for easier testing of the scsi package in
   isolation in the future.
   
   One consequence of this change is it is no longer possible for the
   caller to request a specific UVM path for a SCSI mount. The support for
   this was already kind of a sham, because if the disk was already
   mounted, you would get back its existing mount path instead of the one
   you wanted, so the caller already had to handle that case. Additionally,
   I'm not aware of any reason why the specific location the disk is
   mounted is actually relevant. Because of these reasons, and to simplify
   the overall package interface, the mount path is determined by the scsi
   package, using a format string passed to the Manager at creation time.
   
   Signed-off-by: Kevin Parsons <kevpar@microsoft.com>

   

   kevpar committed May 15, 2023
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