These new callbacks notify the dlm user about lock recovery.
GFS2, and possibly others, need to be aware of when the dlm
will be doing lock recovery for a failed lockspace member.

In the past, this coordination has been done between dlm and
file system daemons in userspace, which then direct their
kernel counterparts.  These callbacks allow the same
coordination directly, and more simply.

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

Slot numbers are assigned to nodes when they join the lockspace.
The slot number chosen is the minimum unused value starting at 1.
Once a node is assigned a slot, that slot number will not change
while the node remains a lockspace member.  If the node leaves
and rejoins it can be assigned a new slot number.

A new generation number is also added to a lockspace.  It is
set and incremented during each recovery along with the slot
collection/assignment.

The slot numbers will be passed to gfs2 which will use them as
journal id's.

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

Put all the calls to recovery barriers in the same function
to clarify where they each happen.  Should not change any behavior.
Also modify some recovery debug lines to make them consistent.

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

Some comments misspell "truly"; this fixes them. No code changes.

Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Replace all GFP_KERNEL and ls_allocation with GFP_NOFS.
ls_allocation would be GFP_KERNEL for userland lockspaces
and GFP_NOFS for file system lockspaces.

It was discovered that any lockspaces on the system can
affect all others by triggering memory reclaim in the
file system which could in turn call back into the dlm
to acquire locks, deadlocking dlm threads that were
shared by all lockspaces, like dlm_recv.

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

Change some GFP_KERNEL allocations to use either GFP_NOFS or
ls_allocation (when available) which the fs sets to GFP_NOFS.
The point is to prevent allocations from going back into the
cluster fs in places where that might lead to deadlock.

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

Make network connections to other nodes earlier, in the context of
dlm_recoverd.  This avoids connecting to nodes from dlm_send where we
try to avoid allocations which could possibly deadlock if memory reclaim
goes into the cluster fs which may try to do a dlm operation.

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

If a node is removed from a lockspace, and then added back before the
dlm is notified of the removal, the dlm will not detect the removal
and won't clear the old state from the node.  This is fixed by using a
list of added nodes so the membership recovery can detect when a newly
added node is already in the member list.

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

Messages from nodes that are no longer members of the lockspace should be
ignored.  When nodes are removed from the lockspace, recovery can
sometimes complete quickly enough that messages arrive from a removed node
after recovery has completed.  When processed, these messages would often
cause an error message, and could in some cases change some state, causing
problems.

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>