The r_req_lru_item list node moves between several lists, and that cycle
is not directly related (and does not begin) with __register_request().
Initialize it in the request constructor, not __register_request(). This
fixes later badness (below) when OSDs restart underneath an rbd mount.
Crashes we've seen due to this include:
[ 213.974288] kernel BUG at net/ceph/messenger.c:2193!
and
[ 144.035274] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
[ 144.035278] IP: [<ffffffffa036c053>] con_work+0x1463/0x2ce0 [libceph]
Signed-off-by: Sage Weil <sage@newdream.net>
935b639a04