3 files changed, 123 insertions, 35 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 78946c6..fdcfbab 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -161,6 +161,7 @@ enum {
 	NFS_STATE_POSIX_LOCKS,		/* Posix locks are supported */
 	NFS_STATE_RECOVERY_FAILED,	/* OPEN stateid state recovery failed */
 	NFS_STATE_MAY_NOTIFY_LOCK,	/* server may CB_NOTIFY_LOCK */
+	NFS_STATE_CHANGE_WAIT,		/* A state changing operation is outstanding */
 };
 
 struct nfs4_state {
@@ -184,6 +185,8 @@ struct nfs4_state {
 	unsigned int n_rdwr;		/* Number of read/write references */
 	fmode_t state;			/* State on the server (R,W, or RW) */
 	atomic_t count;
+
+	wait_queue_head_t waitq;
 };
 
 
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 82e5ed2..cec4bcb 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -1378,6 +1378,25 @@ static bool nfs_open_stateid_recover_openmode(struct nfs4_state *state)
 }
 #endif /* CONFIG_NFS_V4_1 */
 
+static void nfs_state_log_update_open_stateid(struct nfs4_state *state)
+{
+	if (test_and_clear_bit(NFS_STATE_CHANGE_WAIT, &state->flags))
+		wake_up_all(&state->waitq);
+}
+
+static void nfs_state_log_out_of_order_open_stateid(struct nfs4_state *state,
+		const nfs4_stateid *stateid)
+{
+	u32 state_seqid = be32_to_cpu(state->open_stateid.seqid);
+	u32 stateid_seqid = be32_to_cpu(stateid->seqid);
+
+	if (stateid_seqid == state_seqid + 1U ||
+	    (stateid_seqid == 1U && state_seqid == 0xffffffffU))
+		nfs_state_log_update_open_stateid(state);
+	else
+		set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
+}
+
 static void nfs_test_and_clear_all_open_stateid(struct nfs4_state *state)
 {
 	struct nfs_client *clp = state->owner->so_server->nfs_client;
@@ -1393,18 +1412,32 @@ static void nfs_test_and_clear_all_open_stateid(struct nfs4_state *state)
 		nfs4_state_mark_reclaim_nograce(clp, state);
 }
 
+/*
+ * Check for whether or not the caller may update the open stateid
+ * to the value passed in by stateid.
+ *
+ * Note: This function relies heavily on the server implementing
+ * RFC7530 Section 9.1.4.2, and RFC5661 Section 8.2.2
+ * correctly.
+ * i.e. The stateid seqids have to be initialised to 1, and
+ * are then incremented on every state transition.
+ */
 static bool nfs_need_update_open_stateid(struct nfs4_state *state,
-		const nfs4_stateid *stateid, nfs4_stateid *freeme)
+		const nfs4_stateid *stateid)
 {
-	if (test_and_set_bit(NFS_OPEN_STATE, &state->flags) == 0)
-		return true;
-	if (!nfs4_stateid_match_other(stateid, &state->open_stateid)) {
-		nfs4_stateid_copy(freeme, &state->open_stateid);
-		nfs_test_and_clear_all_open_stateid(state);
+	if (test_bit(NFS_OPEN_STATE, &state->flags) == 0 ||
+	    !nfs4_stateid_match_other(stateid, &state->open_stateid)) {
+		if (stateid->seqid == cpu_to_be32(1))
+			nfs_state_log_update_open_stateid(state);
+		else
+			set_bit(NFS_STATE_CHANGE_WAIT, &state->flags);
 		return true;
 	}
-	if (nfs4_stateid_is_newer(stateid, &state->open_stateid))
+
+	if (nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
+		nfs_state_log_out_of_order_open_stateid(state, stateid);
 		return true;
+	}
 	return false;
 }
 
@@ -1443,11 +1476,13 @@ static void nfs_clear_open_stateid_locked(struct nfs4_state *state,
 	if (nfs4_stateid_match_other(stateid, &state->open_stateid) &&
 	    !nfs4_stateid_is_newer(stateid, &state->open_stateid)) {
 		nfs_resync_open_stateid_locked(state);
-		return;
+		goto out;
 	}
 	if (test_bit(NFS_DELEGATED_STATE, &state->flags) == 0)
 		nfs4_stateid_copy(&state->stateid, stateid);
 	nfs4_stateid_copy(&state->open_stateid, stateid);
+out:
+	nfs_state_log_update_open_stateid(state);
 }
 
 static void nfs_clear_open_stateid(struct nfs4_state *state,
@@ -1464,29 +1499,57 @@ static void nfs_clear_open_stateid(struct nfs4_state *state,
 }
 
 static void nfs_set_open_stateid_locked(struct nfs4_state *state,
-		const nfs4_stateid *stateid, fmode_t fmode,
-		nfs4_stateid *freeme)
+		const nfs4_stateid *stateid, nfs4_stateid *freeme)
 {
-	switch (fmode) {
-		case FMODE_READ:
-			set_bit(NFS_O_RDONLY_STATE, &state->flags);
+	DEFINE_WAIT(wait);
+	int status = 0;
+	for (;;) {
+
+		if (!nfs_need_update_open_stateid(state, stateid))
+			return;
+		if (!test_bit(NFS_STATE_CHANGE_WAIT, &state->flags))
 			break;
-		case FMODE_WRITE:
-			set_bit(NFS_O_WRONLY_STATE, &state->flags);
+		if (status)
 			break;
-		case FMODE_READ|FMODE_WRITE:
-			set_bit(NFS_O_RDWR_STATE, &state->flags);
+		/* Rely on seqids for serialisation with NFSv4.0 */
+		if (!nfs4_has_session(NFS_SERVER(state->inode)->nfs_client))
+			break;
+
+		prepare_to_wait(&state->waitq, &wait, TASK_KILLABLE);
+		/*
+		 * Ensure we process the state changes in the same order
+		 * in which the server processed them by delaying the
+		 * update of the stateid until we are in sequence.
+		 */
+		write_sequnlock(&state->seqlock);
+		spin_unlock(&state->owner->so_lock);
+		rcu_read_unlock();
+		if (!signal_pending(current)) {
+			if (schedule_timeout(5*HZ) == 0)
+				status = -EAGAIN;
+			else
+				status = 0;
+		} else
+			status = -EINTR;
+		finish_wait(&state->waitq, &wait);
+		rcu_read_lock();
+		spin_lock(&state->owner->so_lock);
+		write_seqlock(&state->seqlock);
 	}
-	if (!nfs_need_update_open_stateid(state, stateid, freeme))
-		return;
+
+	if (!nfs4_stateid_match_other(stateid, &state->open_stateid)) {
+		nfs4_stateid_copy(freeme, &state->open_stateid);
+		nfs_test_and_clear_all_open_stateid(state);
+	}
+
 	if (test_bit(NFS_DELEGATED_STATE, &state->flags) == 0)
 		nfs4_stateid_copy(&state->stateid, stateid);
 	nfs4_stateid_copy(&state->open_stateid, stateid);
+	nfs_state_log_update_open_stateid(state);
 }
 
-static void __update_open_stateid(struct nfs4_state *state,
+static void nfs_state_set_open_stateid(struct nfs4_state *state,
 		const nfs4_stateid *open_stateid,
-		const nfs4_stateid *deleg_stateid,
 		fmode_t fmode,
 		nfs4_stateid *freeme)
 {
@@ -1494,17 +1557,34 @@ static void __update_open_stateid(struct nfs4_state *state,
 	 * Protect the call to nfs4_state_set_mode_locked and
 	 * serialise the stateid update
 	 */
-	spin_lock(&state->owner->so_lock);
 	write_seqlock(&state->seqlock);
-	if (deleg_stateid != NULL) {
-		nfs4_stateid_copy(&state->stateid, deleg_stateid);
-		set_bit(NFS_DELEGATED_STATE, &state->flags);
+	nfs_set_open_stateid_locked(state, open_stateid, freeme);
+	switch (fmode) {
+	case FMODE_READ:
+		set_bit(NFS_O_RDONLY_STATE, &state->flags);
+		break;
+	case FMODE_WRITE:
+		set_bit(NFS_O_WRONLY_STATE, &state->flags);
+		break;
+	case FMODE_READ|FMODE_WRITE:
+		set_bit(NFS_O_RDWR_STATE, &state->flags);
 	}
-	if (open_stateid != NULL)
-		nfs_set_open_stateid_locked(state, open_stateid, fmode, freeme);
+	set_bit(NFS_OPEN_STATE, &state->flags);
+	write_sequnlock(&state->seqlock);
+}
+
+static void nfs_state_set_delegation(struct nfs4_state *state,
+		const nfs4_stateid *deleg_stateid,
+		fmode_t fmode)
+{
+	/*
+	 * Protect the call to nfs4_state_set_mode_locked and
+	 * serialise the stateid update
+	 */
+	write_seqlock(&state->seqlock);
+	nfs4_stateid_copy(&state->stateid, deleg_stateid);
+	set_bit(NFS_DELEGATED_STATE, &state->flags);
 	write_sequnlock(&state->seqlock);
-	update_open_stateflags(state, fmode);
-	spin_unlock(&state->owner->so_lock);
 }
 
 static int update_open_stateid(struct nfs4_state *state,
@@ -1522,6 +1602,12 @@ static int update_open_stateid(struct nfs4_state *state,
 	fmode &= (FMODE_READ|FMODE_WRITE);
 
 	rcu_read_lock();
+	spin_lock(&state->owner->so_lock);
+	if (open_stateid != NULL) {
+		nfs_state_set_open_stateid(state, open_stateid, fmode, &freeme);
+		ret = 1;
+	}
+
 	deleg_cur = rcu_dereference(nfsi->delegation);
 	if (deleg_cur == NULL)
 		goto no_delegation;
@@ -1538,18 +1624,16 @@ static int update_open_stateid(struct nfs4_state *state,
 		goto no_delegation_unlock;
 
 	nfs_mark_delegation_referenced(deleg_cur);
-	__update_open_stateid(state, open_stateid, &deleg_cur->stateid,
-			fmode, &freeme);
+	nfs_state_set_delegation(state, &deleg_cur->stateid, fmode);
 	ret = 1;
 no_delegation_unlock:
 	spin_unlock(&deleg_cur->lock);
 no_delegation:
+	if (ret)
+		update_open_stateflags(state, fmode);
+	spin_unlock(&state->owner->so_lock);
 	rcu_read_unlock();
 
-	if (!ret && open_stateid != NULL) {
-		__update_open_stateid(state, open_stateid, NULL, fmode, &freeme);
-		ret = 1;
-	}
 	if (test_bit(NFS_STATE_RECLAIM_NOGRACE, &state->flags))
 		nfs4_schedule_state_manager(clp);
 	if (freeme.type != 0)
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 3bd79b8..6e3f372 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -645,6 +645,7 @@ nfs4_alloc_open_state(void)
 	INIT_LIST_HEAD(&state->lock_states);
 	spin_lock_init(&state->state_lock);
 	seqlock_init(&state->seqlock);
+	init_waitqueue_head(&state->waitq);
 	return state;
 }