[3.13.y-ckt stable] Patch "iser-target: Fix implicit termination of connections" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    iser-target: Fix implicit termination of connections

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 7814f0d68aa56fb871759bfd874e2d99846af6c7 Mon Sep 17 00:00:00 2001
From: Sagi Grimberg <sagig at mellanox.com>
Date: Tue, 2 Dec 2014 16:57:29 +0200
Subject: iser-target: Fix implicit termination of connections

commit b02efbfc9a051b41e71fe8f94ddf967260e024a6 upstream.

In situations such as bond failover, The new session establishment
implicitly invokes the termination of the old connection.

So, we don't want to wait for the old connection wait_conn to completely
terminate before we accept the new connection and post a login response.

The solution is to deffer the comp_wait completion and the conn_put to
a work so wait_conn will effectively be non-blocking (flush errors are
assumed to come very fast).

We allocate isert_release_wq with WQ_UNBOUND and WQ_UNBOUND_MAX_ACTIVE
to spread the concurrency of release works.

Reported-by: Slava Shwartsman <valyushash at gmail.com>
Signed-off-by: Sagi Grimberg <sagig at mellanox.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/infiniband/ulp/isert/ib_isert.c | 42 ++++++++++++++++++++++++++-------
 drivers/infiniband/ulp/isert/ib_isert.h |  1 +
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 47d0e0a..a1f194b 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -41,6 +41,7 @@ static DEFINE_MUTEX(device_list_mutex);
 static LIST_HEAD(device_list);
 static struct workqueue_struct *isert_rx_wq;
 static struct workqueue_struct *isert_comp_wq;
+static struct workqueue_struct *isert_release_wq;

 static void
 isert_unmap_cmd(struct isert_cmd *isert_cmd, struct isert_conn *isert_conn);
@@ -2880,6 +2881,24 @@ isert_free_np(struct iscsi_np *np)
 	kfree(isert_np);
 }

+static void isert_release_work(struct work_struct *work)
+{
+	struct isert_conn *isert_conn = container_of(work,
+						     struct isert_conn,
+						     release_work);
+
+	pr_info("Starting release conn %p\n", isert_conn);
+
+	wait_for_completion(&isert_conn->conn_wait);
+
+	mutex_lock(&isert_conn->conn_mutex);
+	isert_conn->state = ISER_CONN_DOWN;
+	mutex_unlock(&isert_conn->conn_mutex);
+
+	pr_info("Destroying conn %p\n", isert_conn);
+	isert_put_conn(isert_conn);
+}
+
 static void isert_wait_conn(struct iscsi_conn *conn)
 {
 	struct isert_conn *isert_conn = conn->context;
@@ -2899,14 +2918,9 @@ static void isert_wait_conn(struct iscsi_conn *conn)
 	mutex_unlock(&isert_conn->conn_mutex);

 	wait_for_completion(&isert_conn->conn_wait_comp_err);
-	wait_for_completion(&isert_conn->conn_wait);
-
-	mutex_lock(&isert_conn->conn_mutex);
-	isert_conn->state = ISER_CONN_DOWN;
-	mutex_unlock(&isert_conn->conn_mutex);

-	pr_info("Destroying conn %p\n", isert_conn);
-	isert_put_conn(isert_conn);
+	INIT_WORK(&isert_conn->release_work, isert_release_work);
+	queue_work(isert_release_wq, &isert_conn->release_work);
 }

 static void isert_free_conn(struct iscsi_conn *conn)
@@ -2952,10 +2966,21 @@ static int __init isert_init(void)
 		goto destroy_rx_wq;
 	}

+	isert_release_wq = alloc_workqueue("isert_release_wq", WQ_UNBOUND,
+					WQ_UNBOUND_MAX_ACTIVE);
+	if (!isert_release_wq) {
+		pr_err("Unable to allocate isert_release_wq\n");
+		ret = -ENOMEM;
+		goto destroy_comp_wq;
+	}
+
 	iscsit_register_transport(&iser_target_transport);
-	pr_debug("iSER_TARGET[0] - Loaded iser_target_transport\n");
+	pr_info("iSER_TARGET[0] - Loaded iser_target_transport\n");
+
 	return 0;

+destroy_comp_wq:
+	destroy_workqueue(isert_comp_wq);
 destroy_rx_wq:
 	destroy_workqueue(isert_rx_wq);
 	return ret;
@@ -2964,6 +2989,7 @@ destroy_rx_wq:
 static void __exit isert_exit(void)
 {
 	flush_scheduled_work();
+	destroy_workqueue(isert_release_wq);
 	destroy_workqueue(isert_comp_wq);
 	destroy_workqueue(isert_rx_wq);
 	iscsit_unregister_transport(&iser_target_transport);
diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index 8a5052e..7429efe 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -126,6 +126,7 @@ struct isert_conn {
 	int			conn_frwr_pool_size;
 	/* lock to protect frwr_pool */
 	spinlock_t		conn_lock;
+	struct work_struct	release_work;
 #define ISERT_COMP_BATCH_COUNT	8
 	int			conn_comp_batch;
 	struct llist_head	conn_comp_llist;
--
1.9.1