The rbtree is a more appropriate data structure than a radix_tree.  It
avoids extra memory usage and simplifies the code.

It also fixes a bug where the debugfs 'mdsc' file wasn't including the
most recent mds request.
Signed-off-by: NSage Weil <sage@newdream.net>

Previously, if the MDS request was interrupted, we would unregister the
request and ignore any reply.  This could cause the caps or other cache
state to become out of sync.  (For instance, aborting dbench and doing
rm -r on clients would complain about a non-empty directory because the
client didn't realize it's aborted file create request completed.)

Even we don't unregister, we still can't process the reply normally because
we are no longer holding the caller's locks (like the dir i_mutex).

So, mark aborted operations with r_aborted, and in the reply handler, be
sure to process all the caps.  Do not process the namespace changes,
though, since we no longer will hold the dir i_mutex.  The dentry lease
state can also be ignored as it's more forgiving.
Signed-off-by: NSage Weil <sage@newdream.net>

Avoid confusing iterate_session_caps(), flag the session while we are
iterating so that __touch_cap does not rearrange items on the list.

All other modifiers of session->s_caps do so under the protection of
s_mutex.
Signed-off-by: NSage Weil <sage@newdream.net>

Signed-off-by: NSage Weil <sage@newdream.net>

When we open a monitor session, we send an initial AUTH message listing
the auth protocols we support, our entity name, and (possibly) a previously
assigned global_id.  The monitor chooses a protocol and responds with an
initial message.

Initially implement AUTH_NONE, a dummy protocol that provides no security,
but works within the new framework.  It generates 'authorizers' that are
used when connecting to (mds, osd) services that simply state our entity
name and global_id.

This is a wire protocol change.
Signed-off-by: NSage Weil <sage@newdream.net>

Unwind initializing if we get ENOMEM during client initialization.
Signed-off-by: NSage Weil <sage@newdream.net>

Signed-off-by: NSage Weil <sage@newdream.net>

We don't get an explicit affirmative confirmation that our caps reconnect,
nor do we necessarily want to pay that cost.  So, take all this code out
for now.
Signed-off-by: NSage Weil <sage@newdream.net>

We were using the cap_gen to track both stale caps (caps that timed out
due to temporarily losing touch with the mds) and dead caps that did not
reconnect after an MDS failure.  Introduce a recon_gen counter to track
reconnections to restarted MDSs and kill dead caps based on that instead.

Rename gen to cap_gen while we're at it to make it more clear which is
which.
Signed-off-by: NSage Weil <sage@newdream.net>

The MDS (metadata server) client is responsible for submitting
requests to the MDS cluster and parsing the response.  We decide which
MDS to submit each request to based on cached information about the
current partition of the directory hierarchy across the cluster.  A
stateful session is opened with each MDS before we submit requests to
it, and a mutex is used to control the ordering of messages within
each session.

An MDS request may generate two responses.  The first indicates the
operation was a success and returns any result.  A second reply is
sent when the operation commits to disk.  Note that locking on the MDS
ensures that the results of updates are visible only to the updating
client before the operation commits.  Requests are linked to the
containing directory so that an fsync will wait for them to commit.

If an MDS fails and/or recovers, we resubmit requests as needed.  We
also reconnect existing capabilities to a recovering MDS to
reestablish that shared session state.  Old dentry leases are
invalidated.
Signed-off-by: NSage Weil <sage@newdream.net>