From 0e03496d1967abf1ebb151a24318c07d07f41f7f Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 17 Jun 2021 10:08:11 -0600
Subject: [PATCH] io-wq: use private CPU mask

In preparation for allowing user specific CPU masks for IO thread
creation, switch to using a mask embedded in the per-node wqe
structure.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io-wq.c | 56 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 46 insertions(+), 10 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 897b94530b57..2af8e1df4646 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -94,6 +94,8 @@ struct io_wqe {
 
 	struct io_wq *wq;
 	struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
+
+	cpumask_var_t cpu_mask;
 };
 
 /*
@@ -638,7 +640,7 @@ fail:
 
 	tsk->pf_io_worker = worker;
 	worker->task = tsk;
-	set_cpus_allowed_ptr(tsk, cpumask_of_node(wqe->node));
+	set_cpus_allowed_ptr(tsk, wqe->cpu_mask);
 	tsk->flags |= PF_NO_SETAFFINITY;
 
 	raw_spin_lock_irq(&wqe->lock);
@@ -922,6 +924,9 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 		wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
 		if (!wqe)
 			goto err;
+		if (!alloc_cpumask_var(&wqe->cpu_mask, GFP_KERNEL))
+			goto err;
+		cpumask_copy(wqe->cpu_mask, cpumask_of_node(node));
 		wq->wqes[node] = wqe;
 		wqe->node = alloc_node;
 		wqe->acct[IO_WQ_ACCT_BOUND].index = IO_WQ_ACCT_BOUND;
@@ -947,8 +952,12 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 err:
 	io_wq_put_hash(data->hash);
 	cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
-	for_each_node(node)
+	for_each_node(node) {
+		if (!wq->wqes[node])
+			continue;
+		free_cpumask_var(wq->wqes[node]->cpu_mask);
 		kfree(wq->wqes[node]);
+	}
 err_wq:
 	kfree(wq);
 	return ERR_PTR(ret);
@@ -1018,6 +1027,7 @@ static void io_wq_destroy(struct io_wq *wq)
 			.cancel_all	= true,
 		};
 		io_wqe_cancel_pending_work(wqe, &match);
+		free_cpumask_var(wqe->cpu_mask);
 		kfree(wqe);
 	}
 	io_wq_put_hash(wq->hash);
@@ -1032,23 +1042,49 @@ void io_wq_put_and_exit(struct io_wq *wq)
 	io_wq_destroy(wq);
 }
 
+struct online_data {
+	unsigned int cpu;
+	bool online;
+};
+
 static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
 {
-	set_cpus_allowed_ptr(worker->task, cpumask_of_node(worker->wqe->node));
+	struct online_data *od = data;
 
+	if (od->online)
+		cpumask_set_cpu(od->cpu, worker->wqe->cpu_mask);
+	else
+		cpumask_clear_cpu(od->cpu, worker->wqe->cpu_mask);
 	return false;
 }
 
+static int __io_wq_cpu_online(struct io_wq *wq, unsigned int cpu, bool online)
+{
+	struct online_data od = {
+		.cpu = cpu,
+		.online = online
+	};
+	int i;
+
+	rcu_read_lock();
+	for_each_node(i)
+		io_wq_for_each_worker(wq->wqes[i], io_wq_worker_affinity, &od);
+	rcu_read_unlock();
+	return 0;
+}
+
 static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
 {
 	struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
-	int i;
 
-	rcu_read_lock();
-	for_each_node(i)
-		io_wq_for_each_worker(wq->wqes[i], io_wq_worker_affinity, NULL);
-	rcu_read_unlock();
-	return 0;
+	return __io_wq_cpu_online(wq, cpu, true);
+}
+
+static int io_wq_cpu_offline(unsigned int cpu, struct hlist_node *node)
+{
+	struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
+
+	return __io_wq_cpu_online(wq, cpu, false);
 }
 
 static __init int io_wq_init(void)
@@ -1056,7 +1092,7 @@ static __init int io_wq_init(void)
 	int ret;
 
 	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "io-wq/online",
-					io_wq_cpu_online, NULL);
+					io_wq_cpu_online, io_wq_cpu_offline);
 	if (ret < 0)
 		return ret;
 	io_wq_online = ret;