NFSv4: Give the lock stateid its own sequence queue

Sharing the open sequence queue causes a deadlock when we try to take
both a lock sequence id and and open sequence id.

This fixes the regression reported by Dimitri Puzin and Jeff Garzik: See

http://bugzilla.kernel.org/show_bug.cgi?id=9712

for details.

Reported-and-tested-by: Dimitri Puzin <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>
Tested-by: Jeff Garzik <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/nfs/nfs4_fs.h

···
 #define NFS_LOCK_INITIALIZED 1
 	int			ls_flags;
 	struct nfs_seqid_counter	ls_seqid;
+	struct rpc_sequence	ls_sequence;
 	struct nfs_unique_id	ls_id;
 	nfs4_stateid		ls_stateid;
 	atomic_t		ls_count;

fs/nfs/nfs4state.c

···
 	lsp = kzalloc(sizeof(*lsp), GFP_KERNEL);
 	if (lsp == NULL)
 		return NULL;
-	lsp->ls_seqid.sequence = &state->owner->so_sequence;
+	rpc_init_wait_queue(&lsp->ls_sequence.wait, "lock_seqid_waitqueue");
+	spin_lock_init(&lsp->ls_sequence.lock);
+	INIT_LIST_HEAD(&lsp->ls_sequence.list);
+	lsp->ls_seqid.sequence = &lsp->ls_sequence;
 	atomic_set(&lsp->ls_count, 1);
 	lsp->ls_owner = fl_owner;
 	spin_lock(&clp->cl_lock);