[PATCH] lightnvm: pblk: set write thread affinity to particular cpu

[Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>]

In some cases write thread migration between cpus can cause
sending writes in improper order and in consequence a lot of
errors from device.

Write thread affinity to particular cpu prevent before it.

Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>
---
 drivers/lightnvm/pblk-init.c | 30 +++++++++++++++++++++++++++++-
 drivers/lightnvm/pblk.h      |  1 +
 drivers/nvme/host/lightnvm.c |  1 +
 include/linux/lightnvm.h     |  2 ++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 81e8ed4..bd25004 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -21,6 +21,8 @@
 
 #include "pblk.h"
 #include "pblk-trace.h"
+#include <linux/cpumask.h>
+#include <linux/numa.h>
 
 static unsigned int write_buffer_size;
 
@@ -47,6 +49,8 @@ struct pblk_global_caches {
 
 struct bio_set pblk_bio_set;
 
+cpumask_t free_cpumask;
+
 static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
 			  struct bio *bio)
 {
@@ -1098,6 +1102,9 @@ static int pblk_lines_init(struct pblk *pblk)
 
 static int pblk_writer_init(struct pblk *pblk)
 {
+	cpumask_t tmp_cpumask, cpumask;
+	int cpu;
+
 	pblk->writer_ts = kthread_create(pblk_write_ts, pblk, "pblk-writer-t");
 	if (IS_ERR(pblk->writer_ts)) {
 		int err = PTR_ERR(pblk->writer_ts);
@@ -1108,6 +1115,22 @@ static int pblk_writer_init(struct pblk *pblk)
 		return err;
 	}
 
+	cpumask_and(&tmp_cpumask, cpumask_of_node(pblk->dev->parent->node),
+			cpu_online_mask);
+	cpumask_and(&cpumask, &tmp_cpumask, &free_cpumask);
+
+	if (!cpumask_weight(&free_cpumask)) {
+		free_cpumask = CPU_MASK_ALL;
+		cpumask_and(&cpumask, &tmp_cpumask, &free_cpumask);
+	}
+
+	cpu = cpumask_last(&cpumask);
+
+	kthread_bind(pblk->writer_ts, cpu);
+
+	cpumask_clear_cpu(cpu, &free_cpumask);
+	pblk->writer_cpu = cpu;
+
 	timer_setup(&pblk->wtimer, pblk_write_timer_fn, 0);
 	mod_timer(&pblk->wtimer, jiffies + msecs_to_jiffies(100));
 
@@ -1126,8 +1149,11 @@ static void pblk_writer_stop(struct pblk *pblk)
 			"Stopping not fully synced write buffer\n");
 
 	del_timer_sync(&pblk->wtimer);
-	if (pblk->writer_ts)
+	if (pblk->writer_ts) {
+		set_cpus_allowed_ptr(pblk->writer_ts, cpu_online_mask);
 		kthread_stop(pblk->writer_ts);
+		cpumask_set_cpu(pblk->writer_cpu, &free_cpumask);
+	}
 }
 
 static void pblk_free(struct pblk *pblk)
@@ -1328,6 +1354,8 @@ static int __init pblk_module_init(void)
 {
 	int ret;
 
+	free_cpumask = CPU_MASK_ALL;
+
 	ret = bioset_init(&pblk_bio_set, BIO_POOL_SIZE, 0, 0);
 	if (ret)
 		return ret;
diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
index 381f074..650f983 100644
--- a/drivers/lightnvm/pblk.h
+++ b/drivers/lightnvm/pblk.h
@@ -690,6 +690,7 @@ struct pblk {
 	atomic_t inflight_io;		/* General inflight I/O counter */
 
 	struct task_struct *writer_ts;
+	int writer_cpu;
 
 	/* Simple translation map of logical addresses to physical addresses.
 	 * The logical addresses is known by the host system, while the physical
diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
index 949e29e..971a19f 100644
--- a/drivers/nvme/host/lightnvm.c
+++ b/drivers/nvme/host/lightnvm.c
@@ -982,6 +982,7 @@ int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node)
 	memcpy(dev->name, disk_name, DISK_NAME_LEN);
 	dev->ops = &nvme_nvm_dev_ops;
 	dev->private_data = ns;
+	dev->node = node;
 	ns->ndev = dev;
 
 	return nvm_register(dev);
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index 5d865a5..312029e 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -427,6 +427,8 @@ struct nvm_dev {
 	char name[DISK_NAME_LEN];
 	void *private_data;
 
+	int node;
+
 	void *rmap;
 
 	struct mutex mlock;
-- 
1.8.3.1