[PATCH V3 5/8] nvme: fix race between freeze queues and unfreeze queues

[Ming Lei]

nvme_dev_disable() and resetting controller are required for recovering
controller, but the two are run from different contexts.

nvme_start_freeze() is run from nvme_dev_disable(), and nvme_unfreeze()
is run from resetting context. Unfortunatley timeout may be triggered
when draining IO from resetting controller, so nvme_start_freeze() may
be run several times.

This patch fixes the race between nvme_start_freeze() and
nvme_unfreeze() by introducing flags of 'queues_freezed' and the lock
of 'freeze_mutex'.

Cc: Jianchao Wang <jianchao.w.w...@oracle.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Sagi Grimberg <s...@grimberg.me>
Cc: linux-n...@lists.infradead.org
Cc: Laurence Oberman <lober...@redhat.com>
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/nvme/host/core.c | 29 +++++++++++++++++++++--------
 drivers/nvme/host/nvme.h |  3 +++
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 9df4f71e58ca..f9028873298e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3447,6 +3447,9 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device 
*dev,
        INIT_WORK(&ctrl->fw_act_work, nvme_fw_act_work);
        INIT_WORK(&ctrl->delete_work, nvme_delete_ctrl_work);
 
+       ctrl->queues_freezed = false;
+       mutex_init(&ctrl->freeze_mutex);
+
        ret = ida_simple_get(&nvme_instance_ida, 0, 0, GFP_KERNEL);
        if (ret < 0)
                goto out;
@@ -3526,10 +3529,15 @@ void nvme_unfreeze(struct nvme_ctrl *ctrl)
 {
        struct nvme_ns *ns;
 
-       down_read(&ctrl->namespaces_rwsem);
-       list_for_each_entry(ns, &ctrl->namespaces, list)
-               blk_mq_unfreeze_queue(ns->queue);
-       up_read(&ctrl->namespaces_rwsem);
+       mutex_lock(&ctrl->freeze_mutex);
+       if (ctrl->queues_freezed) {
+               down_read(&ctrl->namespaces_rwsem);
+               list_for_each_entry(ns, &ctrl->namespaces, list)
+                       blk_mq_unfreeze_queue(ns->queue);
+               up_read(&ctrl->namespaces_rwsem);
+               ctrl->queues_freezed = false;
+       }
+       mutex_unlock(&ctrl->freeze_mutex);
 }
 EXPORT_SYMBOL_GPL(nvme_unfreeze);
 
@@ -3562,10 +3570,15 @@ void nvme_start_freeze(struct nvme_ctrl *ctrl)
 {
        struct nvme_ns *ns;
 
-       down_read(&ctrl->namespaces_rwsem);
-       list_for_each_entry(ns, &ctrl->namespaces, list)
-               blk_freeze_queue_start(ns->queue);
-       up_read(&ctrl->namespaces_rwsem);
+       mutex_lock(&ctrl->freeze_mutex);
+       if (!ctrl->queues_freezed) {
+               down_read(&ctrl->namespaces_rwsem);
+               list_for_each_entry(ns, &ctrl->namespaces, list)
+                       blk_freeze_queue_start(ns->queue);
+               up_read(&ctrl->namespaces_rwsem);
+               ctrl->queues_freezed = true;
+       }
+       mutex_unlock(&ctrl->freeze_mutex);
 }
 EXPORT_SYMBOL_GPL(nvme_start_freeze);
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 061fecfd44f5..a19b7f04ac24 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -149,6 +149,9 @@ struct nvme_ctrl {
        struct work_struct reset_work;
        struct work_struct delete_work;
 
+       bool queues_freezed;
+       struct mutex freeze_mutex;
+
        struct nvme_subsystem *subsys;
        struct list_head subsys_entry;
 
-- 
2.9.5