nvme: switch to RCU freeing the namespace

Switch to RCU freeing the namespace structure so that
nvme_start_queues, nvme_stop_queues and nvme_kill_queues would
be able to get away with only a RCU read side critical section.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimerg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3cf366ab66e94c90d1ee11d3f58a06a036c8353f..3428c02324030d83878350f13fdec1cedc980674 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1429,7 +1429,7 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
        if (nvme_revalidate_disk(ns->disk))
                goto out_free_disk;
 
-       list_add_tail(&ns->list, &ctrl->namespaces);
+       list_add_tail_rcu(&ns->list, &ctrl->namespaces);
        kref_get(&ctrl->kref);
        if (ns->type == NVME_NS_LIGHTNVM)
                return;
@@ -1467,6 +1467,7 @@ static void nvme_ns_remove(struct nvme_ns *ns)
        mutex_lock(&ns->ctrl->namespaces_mutex);
        list_del_init(&ns->list);
        mutex_unlock(&ns->ctrl->namespaces_mutex);
+       synchronize_rcu();
        nvme_put_ns(ns);
 }
 
@@ -1751,8 +1752,8 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 {
        struct nvme_ns *ns;
 
-       mutex_lock(&ctrl->namespaces_mutex);
-       list_for_each_entry(ns, &ctrl->namespaces, list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
                if (!kref_get_unless_zero(&ns->kref))
                        continue;
 
@@ -1769,7 +1770,7 @@ void nvme_kill_queues(struct nvme_ctrl *ctrl)
 
                nvme_put_ns(ns);
        }
-       mutex_unlock(&ctrl->namespaces_mutex);
+       rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(nvme_kill_queues);
 
@@ -1777,8 +1778,8 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl)
 {
        struct nvme_ns *ns;
 
-       mutex_lock(&ctrl->namespaces_mutex);
-       list_for_each_entry(ns, &ctrl->namespaces, list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
                spin_lock_irq(ns->queue->queue_lock);
                queue_flag_set(QUEUE_FLAG_STOPPED, ns->queue);
                spin_unlock_irq(ns->queue->queue_lock);
@@ -1786,7 +1787,7 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl)
                blk_mq_cancel_requeue_work(ns->queue);
                blk_mq_stop_hw_queues(ns->queue);
        }
-       mutex_unlock(&ctrl->namespaces_mutex);
+       rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(nvme_stop_queues);
 
@@ -1794,13 +1795,13 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
 {
        struct nvme_ns *ns;
 
-       mutex_lock(&ctrl->namespaces_mutex);
-       list_for_each_entry(ns, &ctrl->namespaces, list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
                queue_flag_clear_unlocked(QUEUE_FLAG_STOPPED, ns->queue);
                blk_mq_start_stopped_hw_queues(ns->queue, true);
                blk_mq_kick_requeue_list(ns->queue);
        }
-       mutex_unlock(&ctrl->namespaces_mutex);
+       rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(nvme_start_queues);