IB/iser: Post initial receive buffers before sending the final login request

commit 89e984e2c2cd14f77ccb26c47726ac7f13b70ae8 upstream.

An iser target may send iscsi NO-OP PDUs as soon as it marks the iSER
iSCSI session as fully operative.  This means that there is window
where there are no posted receive buffers on the initiator side, so
it's possible for the iSER RC connection to break because of RNR NAK /
retry errors.  To fix this, rely on the flags bits in the login
request to have FFP (0x3) in the lower nibble as a marker for the
final login request, and post an initial chunk of receive buffers
before sending that login request instead of after getting the login
response.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 17 insertions, 13 deletions

diff --git a/drivers/infiniband/ulp/iser/iser_initiator.c b/drivers/infiniband/ulp/iser/iser_initiator.c
index 95a08a8..eb1ee6f 100644
--- a/drivers/infiniband/ulp/iser/iser_initiator.c
+++ b/drivers/infiniband/ulp/iser/iser_initiator.c
@@ -170,7 +170,7 @@ static void iser_create_send_desc(struct iser_conn	*ib_conn,
 }
 
 
-static int iser_alloc_rx_descriptors(struct iser_conn *ib_conn)
+int iser_alloc_rx_descriptors(struct iser_conn *ib_conn)
 {
 	int i, j;
 	u64 dma_addr;
@@ -236,23 +236,24 @@ void iser_free_rx_descriptors(struct iser_conn *ib_conn)
 	kfree(ib_conn->rx_descs);
 }
 
-/**
- *  iser_conn_set_full_featured_mode - (iSER API)
- */
-int iser_conn_set_full_featured_mode(struct iscsi_conn *conn)
+static int iser_post_rx_bufs(struct iscsi_conn *conn, struct iscsi_hdr *req)
 {
 	struct iscsi_iser_conn *iser_conn = conn->dd_data;
 
-	iser_dbg("Initially post: %d\n", ISER_MIN_POSTED_RX);
-
-	/* Check that there is no posted recv or send buffers left - */
-	/* they must be consumed during the login phase */
-	BUG_ON(iser_conn->ib_conn->post_recv_buf_count != 0);
-	BUG_ON(atomic_read(&iser_conn->ib_conn->post_send_buf_count) != 0);
+	iser_dbg("req op %x flags %x\n", req->opcode, req->flags);
+	/* check if this is the last login - going to full feature phase */
+	if ((req->flags & ISCSI_FULL_FEATURE_PHASE) != ISCSI_FULL_FEATURE_PHASE)
+		return 0;
 
-	if (iser_alloc_rx_descriptors(iser_conn->ib_conn))
-		return -ENOMEM;
+	/*
+	 * Check that there is one posted recv buffer (for the last login
+	 * response) and no posted send buffers left - they must have been
+	 * consumed during previous login phases.
+	 */
+	WARN_ON(iser_conn->ib_conn->post_recv_buf_count != 1);
+	WARN_ON(atomic_read(&iser_conn->ib_conn->post_send_buf_count) != 0);
 
+	iser_dbg("Initially post: %d\n", ISER_MIN_POSTED_RX);
 	/* Initial post receive buffers */
 	if (iser_post_recvm(iser_conn->ib_conn, ISER_MIN_POSTED_RX))
 		return -ENOMEM;
@@ -421,6 +422,9 @@ int iser_send_control(struct iscsi_conn *conn,
 		err = iser_post_recvl(iser_conn->ib_conn);
 		if (err)
 			goto send_control_error;
+		err = iser_post_rx_bufs(conn, task->hdr);
+		if (err)
+			goto send_control_error;
 	}
 
 	err = iser_post_send(iser_conn->ib_conn, mdesc);