ceph: fix debugfs entry, simplify fsid checks

We may first learn our fsid from any of the mon, osd, or mds maps
(whichever the monitor sends first).  Consolidate checks in a single
helper.  Initialize the client debugfs entry then, since we need the
fsid (and global_id) for the directory name.

Also remove dead mount code.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 8a28515..8d95b0f 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2782,16 +2782,8 @@
 
 	ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
 	ceph_decode_copy(&p, &fsid, sizeof(fsid));
-        if (mdsc->client->monc.have_fsid) {
-		if (ceph_fsid_compare(&fsid,
-				      &mdsc->client->monc.monmap->fsid)) {
-			pr_err("got mdsmap with wrong fsid\n");
-			return;
-		}
-	} else {
-		ceph_fsid_set(&mdsc->client->monc.monmap->fsid, &fsid);
-		mdsc->client->monc.have_fsid = true;
-	}
+	if (ceph_check_fsid(mdsc->client, &fsid) < 0)
+		return;
 	epoch = ceph_decode_32(&p);
 	maplen = ceph_decode_32(&p);
 	dout("handle_map epoch %u len %d\n", epoch, (int)maplen);