4 files changed, 29 insertions, 4 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index a4cf6d2c14a4..c35932967722 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -454,8 +454,8 @@ static bool referring_call_exists(struct nfs_client *clp,
 				((u32 *)&rclist->rcl_sessionid.data)[3],
 				ref->rc_sequenceid, ref->rc_slotid);
 
-			status = nfs4_slot_seqid_in_use(tbl, ref->rc_slotid,
-					ref->rc_sequenceid);
+			status = nfs4_slot_wait_on_seqid(tbl, ref->rc_slotid,
+					ref->rc_sequenceid, HZ >> 1) < 0;
 			if (status)
 				goto out;
 		}
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 1949bbd806eb..0cc0c319cfdd 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -686,6 +686,8 @@ out_unlock:
 	res->sr_slot = NULL;
 	if (send_new_highest_used_slotid)
 		nfs41_notify_server(session->clp);
+	if (waitqueue_active(&tbl->slot_waitq))
+		wake_up_all(&tbl->slot_waitq);
 }
 
 int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *res)
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index c1f4c208f38a..b62973045a3e 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -28,6 +28,7 @@ static void nfs4_init_slot_table(struct nfs4_slot_table *tbl, const char *queue)
 	tbl->highest_used_slotid = NFS4_NO_SLOT;
 	spin_lock_init(&tbl->slot_tbl_lock);
 	rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, queue);
+	init_waitqueue_head(&tbl->slot_waitq);
 	init_completion(&tbl->complete);
 }
 
@@ -192,7 +193,8 @@ static int nfs4_slot_get_seqid(struct nfs4_slot_table  *tbl, u32 slotid,
  * RPC call in question is still in flight. This function is mainly
  * intended for use by the callback channel.
  */
-bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
+static bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl,
+		u32 slotid, u32 seq_nr)
 {
 	u32 cur_seq;
 	bool ret = false;
@@ -206,6 +208,24 @@ bool nfs4_slot_seqid_in_use(struct nfs4_slot_table *tbl, u32 slotid, u32 seq_nr)
 }
 
 /*
+ * nfs4_slot_wait_on_seqid - wait until a slot sequence id is complete
+ *
+ * Given a slot table, slot id and sequence number, wait until the
+ * corresponding RPC call completes. This function is mainly
+ * intended for use by the callback channel.
+ */
+int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
+		u32 slotid, u32 seq_nr,
+		unsigned long timeout)
+{
+	if (wait_event_timeout(tbl->slot_waitq,
+			!nfs4_slot_seqid_in_use(tbl, slotid, seq_nr),
+			timeout) == 0)
+		return -ETIMEDOUT;
+	return 0;
+}
+
+/*
  * nfs4_alloc_slot - efficiently look for a free slot
  *
  * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.
diff --git a/fs/nfs/nfs4session.h b/fs/nfs/nfs4session.h
index 33cace62b50b..fa75d7db3db3 100644
--- a/fs/nfs/nfs4session.h
+++ b/fs/nfs/nfs4session.h
@@ -36,6 +36,7 @@ struct nfs4_slot_table {
 	unsigned long   used_slots[SLOT_TABLE_SZ]; /* used/unused bitmap */
 	spinlock_t	slot_tbl_lock;
 	struct rpc_wait_queue	slot_tbl_waitq;	/* allocators may wait here */
+	wait_queue_head_t	slot_waitq;	/* Completion wait on slot */
 	u32		max_slots;		/* # slots in table */
 	u32		max_slotid;		/* Max allowed slotid value */
 	u32		highest_used_slotid;	/* sent to server on each SEQ.
@@ -78,7 +79,9 @@ extern int nfs4_setup_slot_table(struct nfs4_slot_table *tbl,
 extern void nfs4_shutdown_slot_table(struct nfs4_slot_table *tbl);
 extern struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl);
 extern struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid);
-extern bool nfs4_slot_seqid_in_use(struct nfs4_slot_table  *tbl, u32 slotid, u32 seq_nr);
+extern int nfs4_slot_wait_on_seqid(struct nfs4_slot_table *tbl,
+		u32 slotid, u32 seq_nr,
+		unsigned long timeout);
 extern bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
 extern void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
 extern void nfs4_slot_tbl_drain_complete(struct nfs4_slot_table *tbl);