[PATCH v5 5/9] scsi: target: iscsit: stop/wait on cmds during conn close

[Mike Christie <michael.christie@oracle.com>]

This fixes a bug added in:

commit f36199355c64 ("scsi: target: iscsi: Fix cmd abort fabric stop
race")

If we have multiple sessions to the same se_device we can hit a race where
a LUN_RESET on one session cleans up the se_cmds from under another
session which is being closed. This results in the closing session freeing
its conn/session structs while they are still in use.

The bug is:

1. Session1 has IO se_cmd1.
2. Session2 can also have se_cmds for IO and optionally TMRs for ABORTS
but then gets a LUN_RESET.
3. The LUN_RESET on session2 sees the se_cmds on session1 and during
the drain stages marks them all with CMD_T_ABORTED.
4. session1 is now closed so iscsit_release_commands_from_conn only sees
se_cmds with the CMD_T_ABORTED bit set and returns immediately even
though we have outstanding commands.
5. session1's connection and session are freed.
6. The backend request for se_cmd1 completes and it accesses the freed
connection/session.

This hooks the iscsit layer into the cmd counter code, so we can wait for
all outstanding se_cmds before freeing the connection.

Fixes: f36199355c64 ("scsi: target: iscsi: Fix cmd abort fabric stop race")
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Maurizio Lombardi <mlombard@redhat.com>
---
 drivers/target/iscsi/iscsi_target.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 11115c207844..83b007141229 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4245,6 +4245,16 @@ static void iscsit_release_commands_from_conn(struct iscsit_conn *conn)
 		iscsit_free_cmd(cmd, true);
 
 	}
+
+	/*
+	 * Wait on commands that were cleaned up via the aborted_task path.
+	 * LLDs that implement iscsit_wait_conn will already have waited for
+	 * commands.
+	 */
+	if (!conn->conn_transport->iscsit_wait_conn) {
+		target_stop_cmd_counter(conn->cmd_cnt);
+		target_wait_for_cmds(conn->cmd_cnt);
+	}
 }
 
 static void iscsit_stop_timers_for_cmds(
-- 
2.25.1