[Xen-devel] [4 Patches] New blktap implementation, 2nd try

[Dutch Meyer <dmeyer@xxxxxxxxx>]

The list filters didn't like the first 2 patches, so I'm reposting the 
whole set from my site. I've also removed the hastily written and 
apparently misleading "less open source" line from the explanation below, 
so that people will stop teasing me.  Rest assured, these patches are 100% 
pure open source.
http://www.cs.ubc.ca/~dmeyer/blktapPatches/deprecate-blktap
http://www.cs.ubc.ca/~dmeyer/blktapPatches/restore-blktap
http://www.cs.ubc.ca/~dmeyer/blktapPatches/fixqcow
http://www.cs.ubc.ca/~dmeyer/blktapPatches/blktap2module

Signed-off-by: Jake Wires <jake.wires@xxxxxxxxxx>, Dutch Meyer 
<dmeyer@xxxxxxxxx>
This is a new and rewritten version of blktap that we have developed at
Citrix.  The current version of blktap is left functionally unmodified.
The change set consists of four patches.

  1) deprecate-blktap. A patch to deprecate the open source blktap, by 
moving it and issuing a warning whenever it is used.  No functionality is 
modified in this patch, it is just housekeeping.
  2) restore-blktap.  A patch to add a new blktap implementation that is 
feature equivalent to (or better than) the current blktap.  This will 
eventually replace the current blktap implementation.
  3) fixqcow.  Fix several bugs in the qcow tools.

  4) blktap2module.  A kernel patch to add a new unified blktap2 module 
that will eventually replace blktap.
The new blktap implementation has several improvements.

  * Isolation from xenstore - Blktap devices can now be created in dom0 as
virtual block devices without coordination from xen and have few
dependencies on xenstore in normal operation.

  * Improved development environment for tapdisks, simpler request
forwarding, new request scheduler.

  * Pause scripts updated to support live qcow snapshot (see xmsnap
script)

  * New tapdisk type: Block Mason disks allow a set of tapdisks to be
flexibly arranged into graph structure and modified on-the-fly.  Several
example modules for Block Mason are included.  Block Mason disks are
constructed and modified with a declarative configuration language.
These capabilities are discussed in more depth in an upcoming paper in the
First Workshop on IO Virtualization, available HERE:
http://www.cs.ubc.ca/~dmeyer/blockmason-wiov-final.pdf

--Dutch

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