[dm-devel] [PATCH v2 0/4] dm pr_ops fixes

[Mike Christie]

The following patches were made over Linus's tree and fix a couple bugs
in the pr_ops code when a reservation type other than one of the All
Registrants types is used. They were tested with the Windows failover
cluster verification tests and libiscsi's PGR tests.

The current dm pr_ops code works well for All Registrants because any
registered path is the reservation holder. Commands like reserve and
release can go down any path and the behavior is the same. The problems
these patches fix is when only one path is the holder as is the case
for the other reservation types which is used by Window Failover Cluster
and Linux Cluster (tools like pacemaker + scsi/multipath_fence agents).
For example for Registrants Only the path that got the RESERVE command is
the reservation holder. The RELEASE must be sent down that path to release
the reservation.

With our current design we send down non-registration PR commands down
whatever path we are currenly using, and then later PR commands end
up on different paths. To continue the current design where dm's pr_ops
are just passing through requests, and to avoid adding PR state to dm
these patches modify pr_reserve/release to work similar to pr_register
where we loop over all paths or at least loop over all paths until we
find the path we are looking for.

v2:
- Added info about testing.
- Added patch for pr_preempt.