Re: [PATCH 11/12] scsi: libiscsi: improve conn_send_pdu API

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On 3/7/22 16:27, Mike Christie wrote:
The conn_send_pdu API is evil in that it returns a pointer to a
iscsi_task, but that task might have been freed already so you can't
touch it. This patch splits the task allocation and transmission, so
functions like iscsi_send_nopout can access the task before its sent and
do whatever book keeping is needed before it's sent.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
  drivers/scsi/libiscsi.c | 85 ++++++++++++++++++++++++++++++-----------
  include/scsi/libiscsi.h |  3 --
  2 files changed, 62 insertions(+), 26 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index cde389225059..a165d4d10cea 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -695,12 +695,18 @@ static int iscsi_prep_mgmt_task(struct iscsi_conn *conn,
  	return 0;
  }
+/**
+ * iscsi_alloc_mgmt_task - allocate and setup a mgmt task.
+ * @conn: iscsi conn that the task will be sent on.
+ * @hdr: iscsi pdu that will be sent.
+ * @data: buffer for data segment if needed.
+ * @data_size: length of data in bytes.
+ */
  static struct iscsi_task *
-__iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
+iscsi_alloc_mgmt_task(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  		      char *data, uint32_t data_size)
  {
  	struct iscsi_session *session = conn->session;
-	struct iscsi_host *ihost = shost_priv(session->host);
  	uint8_t opcode = hdr->opcode & ISCSI_OPCODE_MASK;
  	struct iscsi_task *task;
  	itt_t itt;
@@ -780,28 +786,57 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
  						   task->conn->session->age);
  	}
- if (unlikely(READ_ONCE(conn->ping_task) == INVALID_SCSI_TASK))
-		WRITE_ONCE(conn->ping_task, task);
+	return task;
+
+free_task:
+	iscsi_put_task(task);
+	return NULL;
+}
+
+/**
+ * iscsi_send_mgmt_task - Send task created with iscsi_alloc_mgmt_task.
+ * @task: iscsi task to send.
+ *
+ * On failure this returns a non-zero error code, and the driver must free
+ * the task with iscsi_put_task;
+ */
+static int iscsi_send_mgmt_task(struct iscsi_task *task)
+{
+	struct iscsi_conn *conn = task->conn;
+	struct iscsi_session *session = conn->session;
+	struct iscsi_host *ihost = shost_priv(conn->session->host);
+	int rc = 0;
if (!ihost->workq) {
-		if (iscsi_prep_mgmt_task(conn, task))
-			goto free_task;
+		rc = iscsi_prep_mgmt_task(conn, task);
+		if (rc)
+			return rc;
- if (session->tt->xmit_task(task))
-			goto free_task;
+		rc = session->tt->xmit_task(task);
+		if (rc)
+			return rc;
  	} else {
  		list_add_tail(&task->running, &conn->mgmtqueue);
  		iscsi_conn_queue_xmit(conn);
  	}
- return task;
+	return 0;
+}
-free_task:
-	/* regular RX path uses back_lock */
-	spin_lock(&session->back_lock);
-	__iscsi_put_task(task);
-	spin_unlock(&session->back_lock);
-	return NULL;
+static int __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
+				 char *data, uint32_t data_size)
+{
+	struct iscsi_task *task;
+	int rc;
+
+	task = iscsi_alloc_mgmt_task(conn, hdr, data, data_size);
+	if (!task)
+		return -ENOMEM;
+
+	rc = iscsi_send_mgmt_task(task);
+	if (rc)
+		iscsi_put_task(task);
+	return rc;
  }
int iscsi_conn_send_pdu(struct iscsi_cls_conn *cls_conn, struct iscsi_hdr *hdr,
@@ -812,7 +847,7 @@ int iscsi_conn_send_pdu(struct iscsi_cls_conn *cls_conn, struct iscsi_hdr *hdr,
  	int err = 0;
spin_lock_bh(&session->frwd_lock);
-	if (!__iscsi_conn_send_pdu(conn, hdr, data, data_size))
+	if (__iscsi_conn_send_pdu(conn, hdr, data, data_size))
  		err = -EPERM;
  	spin_unlock_bh(&session->frwd_lock);
  	return err;
@@ -985,7 +1020,6 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
  	if (!rhdr) {
  		if (READ_ONCE(conn->ping_task))
  			return -EINVAL;
-		WRITE_ONCE(conn->ping_task, INVALID_SCSI_TASK);
  	}
memset(&hdr, 0, sizeof(struct iscsi_nopout));
@@ -999,10 +1033,18 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
  	} else
  		hdr.ttt = RESERVED_ITT;
- task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
-	if (!task) {
+	task = iscsi_alloc_mgmt_task(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
+	if (!task)
+		return -ENOMEM;
+
+	if (!rhdr)
+		WRITE_ONCE(conn->ping_task, task);
+
+	if (iscsi_send_mgmt_task(task)) {
  		if (!rhdr)
  			WRITE_ONCE(conn->ping_task, NULL);
+		iscsi_put_task(task);
+
  		iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n");
  		return -EIO;
  	} else if (!rhdr) {
@@ -1869,11 +1911,8 @@ static int iscsi_exec_task_mgmt_fn(struct iscsi_conn *conn,
  	__must_hold(&session->frwd_lock)
  {
  	struct iscsi_session *session = conn->session;
-	struct iscsi_task *task;
- task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)hdr,
-				      NULL, 0);
-	if (!task) {
+	if (__iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)hdr, NULL, 0)) {
  		spin_unlock_bh(&session->frwd_lock);
  		iscsi_conn_printk(KERN_ERR, conn, "Could not send TMF.\n");
  		iscsi_conn_failure(conn, ISCSI_ERR_CONN_FAILED);
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 9032a214104c..412722f44747 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -134,9 +134,6 @@ struct iscsi_task {
  	void			*dd_data;	/* driver/transport data */
  };
-/* invalid scsi_task pointer */
-#define	INVALID_SCSI_TASK	(struct iscsi_task *)-1l
-
  static inline int iscsi_task_has_unsol_data(struct iscsi_task *task)
  {
  	return task->unsol_r2t.data_length > task->unsol_r2t.sent;

Reviewed-by: Lee Duncan <lduncan@xxxxxxxx>




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