This was an ill-conceived feature that has been removed from Ceph.  Do
this gracefully:

 - reject attempts to specify a preferred_osd via the ioctl
 - stop exposing this information via virtual xattrs
 - always fill in -1 for requests, in case we talk to an older server
 - don't calculate preferred_osd placements/pgids
Reviewed-by: NAlex Elder <elder@inktank.com>
Signed-off-by: NSage Weil <sage@inktank.com>

This factors out protocol and low-level storage parts of ceph into a
separate libceph module living in net/ceph and include/linux/ceph.  This
is mostly a matter of moving files around.  However, a few key pieces
of the interface change as well:

 - ceph_client becomes ceph_fs_client and ceph_client, where the latter
   captures the mon and osd clients, and the fs_client gets the mds client
   and file system specific pieces.
 - Mount option parsing and debugfs setup is correspondingly broken into
   two pieces.
 - The mon client gets a generic handler callback for otherwise unknown
   messages (mds map, in this case).
 - The basic supported/required feature bits can be expanded (and are by
   ceph_fs_client).

No functional change, aside from some subtle error handling cases that got
cleaned up in the refactoring process.
Signed-off-by: NSage Weil <sage@newdream.net>

Implement a pool lookup by name.  This will be used by rbd.
Signed-off-by: NYehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: NSage Weil <sage@newdream.net>

OSD requests need to be resubmitted on any pg mapping change, not just when
the pg primary changes.  Resending only when the primary changes results in
occasional 'hung' requests during osd cluster recovery or rebalancing.
Signed-off-by: NSage Weil <sage@newdream.net>

Teach the client to decode an updated format for the osdmap.  The new
format includes pool names, which will be useful shortly.  Get this change
in earlier rather than later.
Signed-off-by: NSage Weil <sage@newdream.net>

Since we can now create and destroy pg pools, the pool ids will be sparse,
and an array no longer makes sense for looking up by pool id.  Use an
rbtree instead.

The OSDMap encoding also no longer has a max pool count (previously used to
allocate the array).  There is a new pool_max, that is the largest pool id
we've ever used, although we don't actually need it in the client.
Signed-off-by: NSage Weil <sage@newdream.net>

The endian conversions don't quite work with the old union ceph_pg.  Just
make it a regular struct, and make each field __le.  This is simpler and it
has the added bonus of actually working.
Signed-off-by: NSage Weil <sage@newdream.net>

The OSD client is responsible for reading and writing data from/to the
object storage pool.  This includes determining where objects are
stored in the cluster, and ensuring that requests are retried or
redirected in the event of a node failure or data migration.

If an OSD does not respond before a timeout expires, keepalive
messages are sent across the lossless, ordered communications channel
to ensure that any break in the TCP is discovered.  If the session
does reset, a reconnection is attempted and affected requests are
resent (by the message transport layer).
Signed-off-by: NSage Weil <sage@newdream.net>