Patch "libiscsi: Fix host busy blocking during connection teardown" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

libiscsi: Fix host busy blocking during connection teardown

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
libiscsi-fix-host-busy-blocking-during-connection-teardown.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: John Soni Jose <[email protected]>
Date: Wed, 24 Jun 2015 06:41:58 +0530
Subject: libiscsi: Fix host busy blocking during connection teardown

From: John Soni Jose <[email protected]>

commit 660d0831d1494a6837b2f810d08b5be092c1f31d upstream.

In case of hw iscsi offload, an host can have N-number of active connections. There can be IO's running on some connections which make host->host_busy always TRUE. Now if logout from a connection is tried then the code gets into an infinite loop as host->host_busy is always TRUE.

iscsi_conn_teardown(....)
{
.........

    /*
     * Block until all in-progress commands for this connection
     * time out or fail.
     */
     for (;;) {
      spin_lock_irqsave(session->host->host_lock, flags);
      if (!atomic_read(&session->host->host_busy)) { /* OK for ERL == 0 */
	      spin_unlock_irqrestore(session->host->host_lock, flags);
              break;
      }
     spin_unlock_irqrestore(session->host->host_lock, flags);
     msleep_interruptible(500);
     iscsi_conn_printk(KERN_INFO, conn, "iscsi conn_destroy(): "
                 "host_busy %d host_failed %d\n",
	          atomic_read(&session->host->host_busy),
	          session->host->host_failed);

	................
	...............
     }

}

This is not an issue with software-iscsi/iser as each cxn is a separate host.

Fix:
Acquiring eh_mutex in iscsi_conn_teardown() before setting session->state = ISCSI_STATE_TERMINATE.

---
 drivers/scsi/libiscsi.c |   25 ++-----------------------
 1 file changed, 2 insertions(+), 23 deletions(-)

@@ -2941,10 +2941,10 @@ void iscsi_conn_teardown(struct iscsi_cl
 {
 	struct iscsi_conn *conn = cls_conn->dd_data;
 	struct iscsi_session *session = conn->session;
-	unsigned long flags;
 
 	del_timer_sync(&conn->transport_timer);
 
+	mutex_lock(&session->eh_mutex);
 	spin_lock_bh(&session->frwd_lock);
 	conn->c_stage = ISCSI_CONN_CLEANUP_WAIT;
 	if (session->leadconn == conn) {

@@ -2956,28 +2956,6 @@ void iscsi_conn_teardown(struct iscsi_cl
 	}
 	spin_unlock_bh(&session->frwd_lock);
 
-	/*
-	 * Block until all in-progress commands for this connection
-	 * time out or fail.
-	 */
-	for (;;) {
-		spin_lock_irqsave(session->host->host_lock, flags);
-		if (!atomic_read(&session->host->host_busy)) { /* OK for ERL == 0 */
-			spin_unlock_irqrestore(session->host->host_lock, flags);
-			break;
-		}
-		spin_unlock_irqrestore(session->host->host_lock, flags);
-		msleep_interruptible(500);
-		iscsi_conn_printk(KERN_INFO, conn, "iscsi conn_destroy(): "
-				  "host_busy %d host_failed %d\n",
-				  atomic_read(&session->host->host_busy),
-				  session->host->host_failed);
-		/*
-		 * force eh_abort() to unblock
-		 */
-		wake_up(&conn->ehwait);
-	}
-
 	/* flush queued up work because we free the connection below */
 	iscsi_suspend_tx(conn);
 

@@ -2994,6 +2972,7 @@ void iscsi_conn_teardown(struct iscsi_cl
 	if (session->leadconn == conn)
 		session->leadconn = NULL;
 	spin_unlock_bh(&session->frwd_lock);
+	mutex_unlock(&session->eh_mutex);
 
 	iscsi_destroy_conn(cls_conn);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/libiscsi-fix-host-busy-blocking-during-connection-teardown.patch