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From:   Wenchao Hao <haowenchao@huawei.com>
To:     Lee Duncan <lduncan@suse.com>, Chris Leech <cleech@redhat.com>,
        "Mike Christie" <michael.christie@oracle.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        <open-iscsi@googlegroups.com>, <linux-scsi@vger.kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <liuzhiqiang26@huawei.com>,
        <linfeilong@huawei.com>, Wenchao Hao <haowenchao@huawei.com>
Subject: [PATCH v7] scsi:iscsi: Fix multiple iscsi session unbind event sent to userspace
Date:   Sat, 26 Nov 2022 09:07:52 +0800
Message-ID: <20221126010752.231917-1-haowenchao@huawei.com>
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I found an issue that kernel would send ISCSI_KEVENT_UNBIND_SESSION
for multiple times which should be fixed.

This patch introduce target_state in iscsi_cls_session to make
sure session would send only one ISCSI_KEVENT_UNBIND_SESSION.

But this would break issue fixed in commit 13e60d3ba287 ("scsi: iscsi:
Report unbind session event when the target has been removed"). The issue
is iscsid died for any reason after it send unbind session to kernel, once
iscsid restart again, it loss kernel's ISCSI_KEVENT_UNBIND_SESSION event.

Now kernel think iscsi_cls_session has already sent an
ISCSI_KEVENT_UNBIND_SESSION event and would not send it any more. Which
would cause userspace unable to logout. Actually the session is in
invalid state(it's target_id is INVALID), iscsid should not sync this
session in it's restart.

So we need to check session's target state during iscsid restart,
if session is in unbound state, do not sync this session and perform
session teardown. It's reasonable because once a session is unbound, we
can not recover it any more(mainly because it's target id is INVALID)

V7:
- Define target state to string map and refer this map directly
- Cleanup __iscsi_unbind_session, drop check for session's
  target_id == ISCSI_MAX_TARGET since it can be handled by target_state

V6:
- Set target state to ALLOCATED in iscsi_add_session
- Rename state BOUND to SCANNED
- Make iscsi_session_target_state_name() more efficient

V5:
- Add ISCSI_SESSION_TARGET_ALLOCATED to indicate the session's
  target has been allocated but not scanned yet. We should
  sync this session and scan this session when iscsid restarted.

V4:
- Move debug print out of spinlock critical section

V3:
- Make target bind state to a state kind rather than a bool.

V2:
- Using target_unbound rather than state to indicate session has been
  unbound

Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
---
 drivers/scsi/scsi_transport_iscsi.c | 47 ++++++++++++++++++++++++++---
 include/scsi/scsi_transport_iscsi.h |  9 ++++++
 2 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index cd3db9684e52..812578c20fe5 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -1676,6 +1676,13 @@ static const char *iscsi_session_state_name(int state)
 	return name;
 }
 
+static char *iscsi_session_target_state_name[] = {
+	[ISCSI_SESSION_TARGET_UNBOUND]   = "UNBOUND",
+	[ISCSI_SESSION_TARGET_ALLOCATED] = "ALLOCATED",
+	[ISCSI_SESSION_TARGET_SCANNED]   = "SCANNED",
+	[ISCSI_SESSION_TARGET_UNBINDING] = "UNBINDING",
+};
+
 int iscsi_session_chkready(struct iscsi_cls_session *session)
 {
 	int err;
@@ -1785,9 +1792,13 @@ static int iscsi_user_scan_session(struct device *dev, void *data)
 		if ((scan_data->channel == SCAN_WILD_CARD ||
 		     scan_data->channel == 0) &&
 		    (scan_data->id == SCAN_WILD_CARD ||
-		     scan_data->id == id))
+		     scan_data->id == id)) {
 			scsi_scan_target(&session->dev, 0, id,
 					 scan_data->lun, scan_data->rescan);
+			spin_lock_irqsave(&session->lock, flags);
+			session->target_state = ISCSI_SESSION_TARGET_SCANNED;
+			spin_unlock_irqrestore(&session->lock, flags);
+		}
 	}
 
 user_scan_exit:
@@ -1960,31 +1971,41 @@ static void __iscsi_unbind_session(struct work_struct *work)
 	struct iscsi_cls_host *ihost = shost->shost_data;
 	unsigned long flags;
 	unsigned int target_id;
+	bool remove_target = true;
 
 	ISCSI_DBG_TRANS_SESSION(session, "Unbinding session\n");
 
 	/* Prevent new scans and make sure scanning is not in progress */
 	mutex_lock(&ihost->mutex);
 	spin_lock_irqsave(&session->lock, flags);
-	if (session->target_id == ISCSI_MAX_TARGET) {
+	if (session->target_state == ISCSI_SESSION_TARGET_ALLOCATED) {
+		remove_target = false;
+	} else if (session->target_state != ISCSI_SESSION_TARGET_SCANNED) {
 		spin_unlock_irqrestore(&session->lock, flags);
 		mutex_unlock(&ihost->mutex);
-		goto unbind_session_exit;
+		ISCSI_DBG_TRANS_SESSION(session,
+			"Skipping target unbinding: Session is unbound/unbinding.\n");
+		return;
 	}
 
+	session->target_state = ISCSI_SESSION_TARGET_UNBINDING;
 	target_id = session->target_id;
 	session->target_id = ISCSI_MAX_TARGET;
 	spin_unlock_irqrestore(&session->lock, flags);
 	mutex_unlock(&ihost->mutex);
 
-	scsi_remove_target(&session->dev);
+	if (remove_target)
+		scsi_remove_target(&session->dev);
 
 	if (session->ida_used)
 		ida_free(&iscsi_sess_ida, target_id);
 
-unbind_session_exit:
 	iscsi_session_event(session, ISCSI_KEVENT_UNBIND_SESSION);
 	ISCSI_DBG_TRANS_SESSION(session, "Completed target removal\n");
+
+	spin_lock_irqsave(&session->lock, flags);
+	session->target_state = ISCSI_SESSION_TARGET_UNBOUND;
+	spin_unlock_irqrestore(&session->lock, flags);
 }
 
 static void __iscsi_destroy_session(struct work_struct *work)
@@ -2061,6 +2082,9 @@ int iscsi_add_session(struct iscsi_cls_session *session, unsigned int target_id)
 		session->ida_used = true;
 	} else
 		session->target_id = target_id;
+	spin_lock_irqsave(&session->lock, flags);
+	session->target_state = ISCSI_SESSION_TARGET_ALLOCATED;
+	spin_unlock_irqrestore(&session->lock, flags);
 
 	dev_set_name(&session->dev, "session%u", session->sid);
 	err = device_add(&session->dev);
@@ -4368,6 +4392,16 @@ iscsi_session_attr(def_taskmgmt_tmo, ISCSI_PARAM_DEF_TASKMGMT_TMO, 0);
 iscsi_session_attr(discovery_parent_idx, ISCSI_PARAM_DISCOVERY_PARENT_IDX, 0);
 iscsi_session_attr(discovery_parent_type, ISCSI_PARAM_DISCOVERY_PARENT_TYPE, 0);
 
+static ssize_t
+show_priv_session_target_state(struct device *dev, struct device_attribute *attr,
+			char *buf)
+{
+	struct iscsi_cls_session *session = iscsi_dev_to_session(dev->parent);
+	return sysfs_emit(buf, "%s\n",
+			iscsi_session_target_state_name[session->target_state]);
+}
+static ISCSI_CLASS_ATTR(priv_sess, target_state, S_IRUGO,
+			show_priv_session_target_state, NULL);
 static ssize_t
 show_priv_session_state(struct device *dev, struct device_attribute *attr,
 			char *buf)
@@ -4470,6 +4504,7 @@ static struct attribute *iscsi_session_attrs[] = {
 	&dev_attr_sess_boot_target.attr,
 	&dev_attr_priv_sess_recovery_tmo.attr,
 	&dev_attr_priv_sess_state.attr,
+	&dev_attr_priv_sess_target_state.attr,
 	&dev_attr_priv_sess_creator.attr,
 	&dev_attr_sess_chap_out_idx.attr,
 	&dev_attr_sess_chap_in_idx.attr,
@@ -4583,6 +4618,8 @@ static umode_t iscsi_session_attr_is_visible(struct kobject *kobj,
 		return S_IRUGO | S_IWUSR;
 	else if (attr == &dev_attr_priv_sess_state.attr)
 		return S_IRUGO;
+	else if (attr == &dev_attr_priv_sess_target_state.attr)
+		return S_IRUGO;
 	else if (attr == &dev_attr_priv_sess_creator.attr)
 		return S_IRUGO;
 	else if (attr == &dev_attr_priv_sess_target_id.attr)
diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
index cab52b0f11d0..34c03707fb6e 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -236,6 +236,14 @@ enum {
 	ISCSI_SESSION_FREE,
 };
 
+enum {
+	ISCSI_SESSION_TARGET_UNBOUND,
+	ISCSI_SESSION_TARGET_ALLOCATED,
+	ISCSI_SESSION_TARGET_SCANNED,
+	ISCSI_SESSION_TARGET_UNBINDING,
+	ISCSI_SESSION_TARGET_MAX,
+};
+
 #define ISCSI_MAX_TARGET -1
 
 struct iscsi_cls_session {
@@ -264,6 +272,7 @@ struct iscsi_cls_session {
 	 */
 	pid_t creator;
 	int state;
+	int target_state;			/* session target bind state */
 	int sid;				/* session id */
 	void *dd_data;				/* LLD private data */
 	struct device dev;	/* sysfs transport/container device */
-- 
2.35.3