Merge patch series "replace old wq(s), added WQ_PERCPU to alloc_workqueue"

Marco Crivellari <marco.crivellari@suse.com> says:

Hi,

=== Current situation: problems ===

Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is
set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected.

This leads to different scenarios if a work item is scheduled on an
isolated CPU where "delay" value is 0 or greater then 0:
        schedule_delayed_work(, 0);

This will be handled by __queue_work() that will queue the work item on the
current local (isolated) CPU, while:

        schedule_delayed_work(, 1);

Will move the timer on an housekeeping CPU, and schedule the work there.

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistency cannot be addressed without refactoring the API.

=== Recent changes to the WQ API ===

The following, address the recent changes in the Workqueue API:

- commit 128ea9f6cc ("workqueue: Add system_percpu_wq and system_dfl_wq")
- commit 930c2ea566 ("workqueue: Add new WQ_PERCPU flag")

The old workqueues will be removed in a future release cycle.

=== Introduced Changes by this series ===

1) [P 1]  Replace uses of system_wq and system_unbound_wq

    system_unbound_wq is to be used when locality is not required.

    Because of that, system_unbound_wq has been replaced with
	system_dfl_wq, to make clear it should be used when locality
	is not required.

2) [P 2-3-4] WQ_PERCPU added to alloc_workqueue()

    This change adds a new WQ_PERCPU flag to explicitly request
    alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.

Thanks!

Link: https://patch.msgid.link/20251031095643.74246-1-marco.crivellari@suse.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/sbp/sbp_target.c

@@ -730,7 +730,7 @@ static int tgt_agent_rw_orb_pointer(struct fw_card *card, int tcode, void *data,
 		pr_debug("tgt_agent ORB_POINTER write: 0x%llx\n",
 				agent->orb_pointer);
 
-		queue_work(system_unbound_wq, &agent->work);
+		queue_work(system_dfl_wq, &agent->work);
 
 		return RCODE_COMPLETE;
 
@@ -764,7 +764,7 @@ static int tgt_agent_rw_doorbell(struct fw_card *card, int tcode, void *data,
 
 		pr_debug("tgt_agent DOORBELL\n");
 
-		queue_work(system_unbound_wq, &agent->work);
+		queue_work(system_dfl_wq, &agent->work);
 
 		return RCODE_COMPLETE;
 
@@ -990,7 +990,7 @@ static void tgt_agent_fetch_work(struct work_struct *work)
 
 		if (tgt_agent_check_active(agent) && !doorbell) {
 			INIT_WORK(&req->work, tgt_agent_process_work);
-			queue_work(system_unbound_wq, &req->work);
+			queue_work(system_dfl_wq, &req->work);
 		} else {
 			/* don't process this request, just check next_ORB */
 			sbp_free_request(req);
@@ -1618,7 +1618,7 @@ static void sbp_mgt_agent_rw(struct fw_card *card,
 		agent->orb_offset = sbp2_pointer_to_addr(ptr);
 		agent->request = req;
 
-		queue_work(system_unbound_wq, &agent->work);
+		queue_work(system_dfl_wq, &agent->work);
 		rcode = RCODE_COMPLETE;
 	} else if (tcode == TCODE_READ_BLOCK_REQUEST) {
 		addr_to_sbp2_pointer(agent->orb_offset, ptr);

drivers/target/target_core_transport.c

@@ -126,12 +126,12 @@ int init_se_kmem_caches(void)
 	}
 
 	target_completion_wq = alloc_workqueue("target_completion",
-					       WQ_MEM_RECLAIM, 0);
+					       WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!target_completion_wq)
 		goto out_free_lba_map_mem_cache;
 
 	target_submission_wq = alloc_workqueue("target_submission",
-					       WQ_MEM_RECLAIM, 0);
+					       WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!target_submission_wq)
 		goto out_free_completion_wq;
 

drivers/target/target_core_xcopy.c

@@ -462,7 +462,7 @@ static const struct target_core_fabric_ops xcopy_pt_tfo = {
 
 int target_xcopy_setup_pt(void)
 {
-	xcopy_wq = alloc_workqueue("xcopy_wq", WQ_MEM_RECLAIM, 0);
+	xcopy_wq = alloc_workqueue("xcopy_wq", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!xcopy_wq) {
 		pr_err("Unable to allocate xcopy_wq\n");
 		return -ENOMEM;

drivers/target/tcm_fc/tfc_conf.c

@@ -250,7 +250,7 @@ static struct se_portal_group *ft_add_tpg(struct se_wwn *wwn, const char *name)
 	tpg->lport_wwn = ft_wwn;
 	INIT_LIST_HEAD(&tpg->lun_list);
 
-	wq = alloc_workqueue("tcm_fc", 0, 1);
+	wq = alloc_workqueue("tcm_fc", WQ_PERCPU, 1);
 	if (!wq) {
 		kfree(tpg);
 		return NULL;