ceph: warn on allocation from msgpool with larger front_len

Pass the front_len we need when pulling a message off a msgpool,
and WARN if it is greater than the pool's size.  Then try to
allocate a new message (to continue without failing).

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/mon_client.c b/fs/ceph/mon_client.c
index d52e529..e6e954c 100644
--- a/fs/ceph/mon_client.c
+++ b/fs/ceph/mon_client.c
@@ -639,14 +639,15 @@
 {
 	struct ceph_mon_client *monc = con->private;
 	int type = le16_to_cpu(hdr->type);
+	int front = le32_to_cpu(hdr->front_len);
 
 	switch (type) {
 	case CEPH_MSG_CLIENT_MOUNT_ACK:
-		return ceph_msgpool_get(&monc->msgpool_mount_ack);
+		return ceph_msgpool_get(&monc->msgpool_mount_ack, front);
 	case CEPH_MSG_MON_SUBSCRIBE_ACK:
-		return ceph_msgpool_get(&monc->msgpool_subscribe_ack);
+		return ceph_msgpool_get(&monc->msgpool_subscribe_ack, front);
 	case CEPH_MSG_STATFS_REPLY:
-		return ceph_msgpool_get(&monc->msgpool_statfs_reply);
+		return ceph_msgpool_get(&monc->msgpool_statfs_reply, front);
 	}
 	return ceph_alloc_msg(con, hdr);
 }