Re: [PATCH] libiscsi: Fix iscsi_check_transport_timeouts possible infinite loop

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On 6/30/15, 9:55 AM, Sagi Grimberg wrote:
From: Ariel Nahum <arieln@xxxxxxxxxxxx>

Connection last_ping is not being updated when iscsi_send_nopout fails.
Not updating the last_ping will cause firing a timer to a past time
(last_ping + ping_tmo < current_time) which triggers an infinite loop of
iscsi_check_transport_timeouts() and hogs the cpu.

Fix this issue by checking the return value of iscsi_send_nopout.
If it fails set the next_timeout to one second later.

Signed-off-by: Ariel Nahum <arieln@xxxxxxxxxxxx>
Signed-off-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
---
  drivers/scsi/libiscsi.c |   15 ++++++++++-----
  1 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 8053f24..1ea4213 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -979,13 +979,13 @@ static void iscsi_tmf_rsp(struct iscsi_conn *conn, struct iscsi_hdr *hdr)
  	wake_up(&conn->ehwait);
  }

-static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
+static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
  {
          struct iscsi_nopout hdr;
  	struct iscsi_task *task;

  	if (!rhdr && conn->ping_task)
-		return;
+		return -EINVAL;

  	memset(&hdr, 0, sizeof(struct iscsi_nopout));
  	hdr.opcode = ISCSI_OP_NOOP_OUT | ISCSI_OP_IMMEDIATE;
@@ -999,13 +999,16 @@ static void iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
  		hdr.ttt = RESERVED_ITT;

  	task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
-	if (!task)
+	if (!task) {


Are you hitting the failure case in the first chunk of the patch or the failure right above? If the latter, why is it failing?

  		iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n");
+		return -EIO;
+	}
  	else if (!rhdr) {

I think the coding style is wrong. It should be:

if () {

} else if {

}

  		/* only track our nops */
  		conn->ping_task = task;
  		conn->last_ping = jiffies;
  	}
+	return 0;
  }

  static int iscsi_nop_out_rsp(struct iscsi_task *task,
@@ -2095,8 +2098,10 @@ static void iscsi_check_transport_timeouts(unsigned long data)
  	if (time_before_eq(last_recv + recv_timeout, jiffies)) {
  		/* send a ping to try to provoke some traffic */
  		ISCSI_DBG_CONN(conn, "Sending nopout as ping\n");
-		iscsi_send_nopout(conn, NULL);
-		next_timeout = conn->last_ping + (conn->ping_timeout * HZ);
+		if (iscsi_send_nopout(conn, NULL))
+			next_timeout = jiffies + (1 * HZ);
+		else
+			next_timeout = conn->last_ping + (conn->ping_timeout * HZ);
  	} else
  		next_timeout = last_recv + recv_timeout;


n
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