[PATCH] nvme: add 'fail_if_no_path' sysfs attribute

[PATCH] nvme: add 'fail_if_no_path' sysfs attribute

[Hannes Reinecke]

In some setups like RAID we need to return an I/O error
once all paths are unavailable to allow the upper layers
to start their own error recovery (like redirecting I/O
to other mirrors).
This patch adds a sysfs attribute 'fail_if_no_path' to
allow the admin to enable that behaviour instead of the
current 'queue until a path becomes available' policy.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/host/core.c      |  5 +++++
 drivers/nvme/host/multipath.c | 36 ++++++++++++++++++++++++++++++++++-
 drivers/nvme/host/nvme.h      |  2 ++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 9879153d8d28..eee42d0b3400 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3440,6 +3440,7 @@ static struct attribute *nvme_ns_id_attrs[] = {
 #ifdef CONFIG_NVME_MULTIPATH
 	&dev_attr_ana_grpid.attr,
 	&dev_attr_ana_state.attr,
+	&dev_attr_fail_if_no_path.attr,
 #endif
 	NULL,
 };
@@ -3470,6 +3471,10 @@ static umode_t nvme_ns_id_attrs_are_visible(struct kobject *kobj,
 		if (!nvme_ctrl_use_ana(nvme_get_ns_from_dev(dev)->ctrl))
 			return 0;
 	}
+	if (a == &dev_attr_fail_if_no_path.attr) {
+		if (dev_to_disk(dev)->fops == &nvme_bdev_ops)
+			return 0;
+	}
 #endif
 	return a->mode;
 }
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 9ac762b28811..47fecb3f9434 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -283,10 +283,13 @@ static bool nvme_available_path(struct nvme_ns_head *head)
 			continue;
 		switch (ns->ctrl->state) {
 		case NVME_CTRL_LIVE:
+			return true;
 		case NVME_CTRL_RESETTING:
 		case NVME_CTRL_CONNECTING:
 			/* fallthru */
-			return true;
+			if (!test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH,
+				      &head->flags))
+				return true;
 		default:
 			break;
 		}
@@ -641,6 +644,37 @@ static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
 }
 DEVICE_ATTR_RO(ana_state);
 
+static ssize_t fail_if_no_path_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct nvme_ns_head *head = disk->private_data;
+
+	return sprintf(buf, "%d\n",
+		       test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags) ?
+		       1 : 0);
+}
+
+static ssize_t fail_if_no_path_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct gendisk *disk = dev_to_disk(dev);
+	struct nvme_ns_head *head = disk->private_data;
+	int fail_if_no_path, err;
+
+	err = kstrtoint(buf, 10, &fail_if_no_path);
+	if (err)
+		return -EINVAL;
+
+	else if (fail_if_no_path <= 0)
+		clear_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);
+	else
+		set_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);
+	return count;
+}
+DEVICE_ATTR(fail_if_no_path, S_IRUGO | S_IWUSR,
+	fail_if_no_path_show, fail_if_no_path_store);
+
 static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl,
 		struct nvme_ana_group_desc *desc, void *data)
 {
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 09d142a9628c..f3ba741d44d0 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -411,6 +411,7 @@ struct nvme_ns_head {
 	struct mutex		lock;
 	unsigned long		flags;
 #define NVME_NSHEAD_DISK_LIVE	0
+#define NVME_NSHEAD_FAIL_IF_NO_PATH	1
 	struct nvme_ns __rcu	*current_path[];
 #endif
 };
@@ -684,6 +685,7 @@ static inline void nvme_trace_bio_complete(struct request *req)
 
 extern struct device_attribute dev_attr_ana_grpid;
 extern struct device_attribute dev_attr_ana_state;
+extern struct device_attribute dev_attr_fail_if_no_path;
 extern struct device_attribute subsys_attr_iopolicy;
 
 #else
-- 
2.29.2


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Re: [PATCH] nvme: add 'fail_if_no_path' sysfs attribute

[Keith Busch]

On Fri, Feb 19, 2021 at 03:46:25PM +0100, Hannes Reinecke wrote:
> In some setups like RAID we need to return an I/O error
> once all paths are unavailable to allow the upper layers
> to start their own error recovery (like redirecting I/O
> to other mirrors).
> This patch adds a sysfs attribute 'fail_if_no_path' to
> allow the admin to enable that behaviour instead of the
> current 'queue until a path becomes available' policy.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>

Sounds okay to me, just some minor nits below.

> @@ -283,10 +283,13 @@ static bool nvme_available_path(struct nvme_ns_head *head)
>  			continue;
>  		switch (ns->ctrl->state) {
>  		case NVME_CTRL_LIVE:
> +			return true;
>  		case NVME_CTRL_RESETTING:
>  		case NVME_CTRL_CONNECTING:
>  			/* fallthru */
> -			return true;
> +			if (!test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH,
> +				      &head->flags))
> +				return true;

It doesn't look like the 'fallthru' is in the right place anymore,
though I can't tell why it is there in the first place.

>  		default:
>  			break;
>  		}
> @@ -641,6 +644,37 @@ static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
>  }
>  DEVICE_ATTR_RO(ana_state);
>  
> +static ssize_t fail_if_no_path_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	struct gendisk *disk = dev_to_disk(dev);
> +	struct nvme_ns_head *head = disk->private_data;
> +
> +	return sprintf(buf, "%d\n",
> +		       test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags) ?
> +		       1 : 0);
> +}
> +
> +static ssize_t fail_if_no_path_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t count)
> +{
> +	struct gendisk *disk = dev_to_disk(dev);
> +	struct nvme_ns_head *head = disk->private_data;
> +	int fail_if_no_path, err;
> +
> +	err = kstrtoint(buf, 10, &fail_if_no_path);
> +	if (err)
> +		return -EINVAL;
> +
> +	else if (fail_if_no_path <= 0)
> +		clear_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);
> +	else
> +		set_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);

The extra line above the 'else if' should be removed, or just change it
to simply 'if'.

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Re: [PATCH] nvme: add 'fail_if_no_path' sysfs attribute

[Hannes Reinecke]

On 2/20/21 12:16 AM, Keith Busch wrote:
> On Fri, Feb 19, 2021 at 03:46:25PM +0100, Hannes Reinecke wrote:
>> In some setups like RAID we need to return an I/O error
>> once all paths are unavailable to allow the upper layers
>> to start their own error recovery (like redirecting I/O
>> to other mirrors).
>> This patch adds a sysfs attribute 'fail_if_no_path' to
>> allow the admin to enable that behaviour instead of the
>> current 'queue until a path becomes available' policy.
>>
>> Signed-off-by: Hannes Reinecke <hare@suse.de>
> 
> Sounds okay to me, just some minor nits below.
> 
>> @@ -283,10 +283,13 @@ static bool nvme_available_path(struct nvme_ns_head *head)
>>   			continue;
>>   		switch (ns->ctrl->state) {
>>   		case NVME_CTRL_LIVE:
>> +			return true;
>>   		case NVME_CTRL_RESETTING:
>>   		case NVME_CTRL_CONNECTING:
>>   			/* fallthru */
>> -			return true;
>> +			if (!test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH,
>> +				      &head->flags))
>> +				return true;
> 
> It doesn't look like the 'fallthru' is in the right place anymore,
> though I can't tell why it is there in the first place.
> 
Indeed, the 'fallthru' is misplaced; it needs to go after
NVME_CTRL_RESETTING.

>>   		default:
>>   			break;
>>   		}
>> @@ -641,6 +644,37 @@ static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
>>   }
>>   DEVICE_ATTR_RO(ana_state);
>>   
>> +static ssize_t fail_if_no_path_show(struct device *dev,
>> +		struct device_attribute *attr, char *buf)
>> +{
>> +	struct gendisk *disk = dev_to_disk(dev);
>> +	struct nvme_ns_head *head = disk->private_data;
>> +
>> +	return sprintf(buf, "%d\n",
>> +		       test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags) ?
>> +		       1 : 0);
>> +}
>> +
>> +static ssize_t fail_if_no_path_store(struct device *dev,
>> +		struct device_attribute *attr, const char *buf, size_t count)
>> +{
>> +	struct gendisk *disk = dev_to_disk(dev);
>> +	struct nvme_ns_head *head = disk->private_data;
>> +	int fail_if_no_path, err;
>> +
>> +	err = kstrtoint(buf, 10, &fail_if_no_path);
>> +	if (err)
>> +		return -EINVAL;
>> +
>> +	else if (fail_if_no_path <= 0)
>> +		clear_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);
>> +	else
>> +		set_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags);
> 
> The extra line above the 'else if' should be removed, or just change it
> to simply 'if'.
> 
Sure.

I'll be resending.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

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