[dm-devel] 2.6.10-rc1-udm2: multipath updates

[Alasdair G Kergon]

ftp://sources.redhat.com/pub/dm/patches/2.6-unstable/2.6.10-rc1/2.6.10-rc1-udm1.tar.bz2

New patches since udm1:
  Patch 6 - dm-crypt fix for zero-length keys
  Patch 10 - fix some badly-formatted error messages
  Patches 15-33 - updates to multipath code as discussed on list

A few features aren't used by anything yet, and may get removed for
the first submission upstream if no code needing them emerges before then.

Updated table example:
   0 96000 multipath 
   1 queue_if_no_path 0 1 1 round-robin 0 2 1 7:1 1 7:2 1
                          ^ Index of the group to try first
                                        ^ Number of round-robin args

Updated status example:
  0 96000 multipath 1 0 0 1 1 A 0 2 0 7:1 F 2 7:2 A 1
                            ^ Group number to be used next
                                ^ Number of round-robin args

New message
  switch_group - use the specified group for the next I/O onwards
  This also re-enables all the groups.

e.g. dmsetup message mp3 0 switch_group 2

Reinstating a path in a higher-priority group no longer causes the group
to switch.

suspend switches to fail_if_no_path and waits for the queue to empty.
If queue_if_no_path was set, resume will reenable it.

Alasdair
-- 
agk at redhat.com