Add an option (disabled by default) to print a warning message
when a lock has been waiting a configurable amount of time for
a reply message from another node.  This is mainly for debugging.

Signed-off-by: David Teigland <teigland@redhat.com>

dlm_print_rsb() can now become static.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: David Teigland <teigland@redhat.com>

* check that length is large enough to cover the non-variable part of message or
  rcom resp. (after checking that it's large enough to cover the header, of
  course).

* kill more pointless casts

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Teigland <teigland@redhat.com>

To prevent the master of an rsb from changing rapidly, an unused rsb is kept
on the "toss list" for a period of time to be reused.  The toss list was
being cleared completely for each recovery, which is unnecessary.  Much of
the benefit of the toss list can be maintained if nodes keep rsb's in their
toss list that they are the master of.  These rsb's need to be included
when the resource directory is rebuilt during recovery.

Signed-off-by: David Teigland <teigland@redhat.com>

Introduce a per-lockspace rwsem that's held in read mode by dlm_recv
threads while working in the dlm.  This allows dlm_recv activity to be
suspended when the lockspace transitions to, from and between recovery
cycles.

The specific bug prompting this change is one where an in-progress
recovery cycle is aborted by a new recovery cycle.  While dlm_recv was
processing a recovery message, the recovery cycle was aborted and
dlm_recoverd began cleaning up.  dlm_recv decremented recover_locks_count
on an rsb after dlm_recoverd had reset it to zero.  This is fixed by
suspending dlm_recv (taking write lock on the rwsem) before aborting the
current recovery.

The transitions to/from normal and recovery modes are simplified by using
this new ability to block dlm_recv.  The switch from normal to recovery
mode means dlm_recv goes from processing locking messages, to saving them
for later, and vice versa.  Races are avoided by blocking dlm_recv when
setting the flag that switches between modes.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

Add a function that can be used through libdlm by a system daemon to cancel
another process's deadlocked lock.  A completion ast with EDEADLK is returned
to the process waiting for the lock.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

Change the user/kernel device interface used by libdlm:
- Add ability for userspace to check the version of the interface.  libdlm
  can now adapt to different versions of the kernel interface.
- Increase the size of the flags passed in a lock request so all possible
  flags can be used from userspace.
- Add an opaque "xid" value for each lock.  This "transaction id" will be
  used later to associate locks with each other during deadlock detection.
- Add a "timeout" value for each lock.  This is used along with the
  DLM_LKF_TIMEOUT flag.

Also, remove a fragment of unused code in device_read().

This patch requires updating libdlm which is backward compatible with
older kernels.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

New features: lock timeouts and time warnings.  If the DLM_LKF_TIMEOUT
flag is set, then the request/conversion will be canceled after waiting
the specified number of centiseconds (specified per lock).  This feature
is only available for locks requested through libdlm (can be enabled for
kernel dlm users if there's a use for it.)

If the new DLM_LSFL_TIMEWARN flag is set when creating the lockspace, then
a warning message will be sent to userspace (using genetlink) after a
request/conversion has been waiting for a given number of centiseconds
(configurable per node).  The time warnings will be used in the future
to do deadlock detection in userspace.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

Don't let dlm_scand run during recovery since it may try to do a resource
directory removal while the directory nodes are changing.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

Add code to accept purge commands from userland.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>