scsi: iscsi: Use system_unbound_wq for destroy_work

stable inclusion
from stable-v5.10.112
commit 22608545b834b855c0a7fd9f675edc884b7d21a3
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5HL0X

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22608545b834b855c0a7fd9f675edc884b7d21a3

--------------------------------

[ Upstream commit b25b957d ]

Use the system_unbound_wq for async session destruction. We don't need a
dedicated workqueue for async session destruction because:

 1. perf does not seem to be an issue since we only allow 1 active work.

 2. it does not have deps with other system works and we can run them in
    parallel with each other.

Link: https://lore.kernel.org/r/20210525181821.7617-6-michael.christie@oracle.comReviewed-by: NLee Duncan <lduncan@suse.com>
Signed-off-by: NMike Christie <michael.christie@oracle.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/scsi/scsi_transport_iscsi.c

@@ -95,8 +95,6 @@ static DECLARE_WORK(stop_conn_work, stop_conn_work_fn);
 static atomic_t iscsi_session_nr; /* sysfs session id for next new session */
 static struct workqueue_struct *iscsi_eh_timer_workq;
 
-static struct workqueue_struct *iscsi_destroy_workq;
-
 static DEFINE_IDA(iscsi_sess_ida);
 /*
  * list of registered transports and lock that must
@@ -3717,7 +3715,7 @@ iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, uint32_t *group)
 			list_del_init(&session->sess_list);
 			spin_unlock_irqrestore(&sesslock, flags);
 
-			queue_work(iscsi_destroy_workq, &session->destroy_work);
+			queue_work(system_unbound_wq, &session->destroy_work);
 		}
 		break;
 	case ISCSI_UEVENT_UNBIND_SESSION:
@@ -4813,18 +4811,8 @@ static __init int iscsi_transport_init(void)
 		goto release_nls;
 	}
 
-	iscsi_destroy_workq = alloc_workqueue("%s",
-			WQ_SYSFS | __WQ_LEGACY | WQ_MEM_RECLAIM | WQ_UNBOUND,
-			1, "iscsi_destroy");
-	if (!iscsi_destroy_workq) {
-		err = -ENOMEM;
-		goto destroy_wq;
-	}
-
 	return 0;
 
-destroy_wq:
-	destroy_workqueue(iscsi_eh_timer_workq);
 release_nls:
 	netlink_kernel_release(nls);
 unregister_flashnode_bus:
@@ -4846,7 +4834,6 @@ static __init int iscsi_transport_init(void)
 
 static void __exit iscsi_transport_exit(void)
 {
-	destroy_workqueue(iscsi_destroy_workq);
 	destroy_workqueue(iscsi_eh_timer_workq);
 	netlink_kernel_release(nls);
 	bus_unregister(&iscsi_flashnode_bus);