[PATCH] nvme-fc: Implement async-connect option

[PATCH] nvme-fc: Implement async-connect option

[Hannes Reinecke]

By opening the control fd with O_NONBLOCK the fabrics module will
attempt an async connect if implemented.
This is especially useful when calling 'nvme connect' from an udev
rule, as there each program should return as fast as possible to
avoid an udev event processing stall.

Signed-off-by: Hannes Reinecke <hare at suse.com>
---
 drivers/nvme/host/fabrics.c |  9 ++++++---
 drivers/nvme/host/fabrics.h |  1 +
 drivers/nvme/host/fc.c      | 10 +++++++++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 76b4fe6..b577e7e 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -568,6 +568,7 @@ static int nvmf_parse_options(struct nvmf_ctrl_options *opts,
 	opts->reconnect_delay = NVMF_DEF_RECONNECT_DELAY;
 	opts->kato = NVME_DEFAULT_KATO;
 	opts->duplicate_connect = false;
+	opts->async_connect = false;
 
 	options = o = kstrdup(buf, GFP_KERNEL);
 	if (!options)
@@ -831,7 +832,7 @@ void nvmf_free_options(struct nvmf_ctrl_options *opts)
 				 NVMF_OPT_HOST_ID | NVMF_OPT_DUP_CONNECT)
 
 static struct nvme_ctrl *
-nvmf_create_ctrl(struct device *dev, const char *buf, size_t count)
+nvmf_create_ctrl(struct device *dev, const char *buf, size_t count, bool async)
 {
 	struct nvmf_ctrl_options *opts;
 	struct nvmf_transport_ops *ops;
@@ -846,6 +847,7 @@ void nvmf_free_options(struct nvmf_ctrl_options *opts)
 	if (ret)
 		goto out_free_opts;
 
+	opts->async_connect = async;
 
 	request_module("nvme-%s", opts->transport);
 
@@ -882,7 +884,7 @@ void nvmf_free_options(struct nvmf_ctrl_options *opts)
 		goto out_unlock;
 	}
 
-	if (strcmp(ctrl->subsys->subnqn, opts->subsysnqn)) {
+	if (ctrl->subsys && strcmp(ctrl->subsys->subnqn, opts->subsysnqn)) {
 		dev_warn(ctrl->device,
 			"controller returned incorrect NQN: \"%s\".\n",
 			ctrl->subsys->subnqn);
@@ -926,7 +928,8 @@ static ssize_t nvmf_dev_write(struct file *file, const char __user *ubuf,
 		goto out_unlock;
 	}
 
-	ctrl = nvmf_create_ctrl(nvmf_device, buf, count);
+	ctrl = nvmf_create_ctrl(nvmf_device, buf, count,
+				file->f_flags & O_NONBLOCK);
 	if (IS_ERR(ctrl)) {
 		ret = PTR_ERR(ctrl);
 		goto out_unlock;
diff --git a/drivers/nvme/host/fabrics.h b/drivers/nvme/host/fabrics.h
index 9ba6149..081c94c 100644
--- a/drivers/nvme/host/fabrics.h
+++ b/drivers/nvme/host/fabrics.h
@@ -98,6 +98,7 @@ struct nvmf_ctrl_options {
 	unsigned int		reconnect_delay;
 	bool			discovery_nqn;
 	bool			duplicate_connect;
+	bool			async_connect;
 	unsigned int		kato;
 	struct nvmf_host	*host;
 	int			max_reconnects;
diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 26ff51b..fc0a7b8 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3190,6 +3190,14 @@ static inline blk_status_t nvme_fc_is_ready(struct nvme_fc_queue *queue,
 	list_add_tail(&ctrl->ctrl_list, &rport->ctrl_list);
 	spin_unlock_irqrestore(&rport->lock, flags);
 
+	if (ctrl->ctrl.opts->async_connect) {
+		nvme_get_ctrl(&ctrl->ctrl);
+		dev_info(ctrl->ctrl.device,
+			"NVME-FC{%d}: starting async-connect\n", ctrl->cnum);
+		queue_delayed_work(nvme_wq, &ctrl->connect_work, 0);
+		goto done;
+	}
+
 	/*
 	 * It's possible that transactions used to create the association
 	 * may fail. Examples: CreateAssociation LS or CreateIOConnection
@@ -3243,7 +3251,7 @@ static inline blk_status_t nvme_fc_is_ready(struct nvme_fc_queue *queue,
 	}
 
 	nvme_get_ctrl(&ctrl->ctrl);
-
+done:
 	dev_info(ctrl->ctrl.device,
 		"NVME-FC{%d}: new ctrl: NQN \"%s\"\n",
 		ctrl->cnum, ctrl->ctrl.opts->subsysnqn);
-- 
1.8.5.6

[PATCH] nvme-fc: Implement async-connect option

[James Smart]

On 12/5/2017 12:04 AM, Hannes Reinecke wrote:
> By opening the control fd with O_NONBLOCK the fabrics module will
> attempt an async connect if implemented.
> This is especially useful when calling 'nvme connect' from an udev
> rule, as there each program should return as fast as possible to
> avoid an udev event processing stall.
>
> Signed-off-by: Hannes Reinecke <hare at suse.com>
>

This seems odd.?? I would have thought any async connect option would 
have been isolated in the fabrics.c file and applicable to any transport.

I can understand why this works as fc is well suited for this division 
(allocates ctrl 1st, then makes 1st connection in same style as 
reconnects). But the other transports aren't structure the same way so 
they're going to be a bit more trouble.

-- james

[PATCH] nvme-fc: Implement async-connect option

[Hannes Reinecke]

On 12/05/2017 08:41 PM, James Smart wrote:
> On 12/5/2017 12:04 AM, Hannes Reinecke wrote:
>> By opening the control fd with O_NONBLOCK the fabrics module will
>> attempt an async connect if implemented.
>> This is especially useful when calling 'nvme connect' from an udev
>> rule, as there each program should return as fast as possible to
>> avoid an udev event processing stall.
>>
>> Signed-off-by: Hannes Reinecke <hare at suse.com>
>>
> 
> This seems odd.?? I would have thought any async connect option would
> have been isolated in the fabrics.c file and applicable to any transport.
> 
Possibly.

> I can understand why this works as fc is well suited for this division
> (allocates ctrl 1st, then makes 1st connection in same style as
> reconnects). But the other transports aren't structure the same way so
> they're going to be a bit more trouble.
> 
That was actually my plan; I actually looking into making the
connect/reconnect workqueue function the default, and drop the
distinction between 1st connect and reconnect.
With that the only difference between 'async' and normal connect would
be the delay when scheduling the workqueue item.

But RDMA turned out to be a bit more complex, so I did this patch first
to gauge response.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare at suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
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