[PATCH] nvme-multipath: require exact iopolicy names for module parameter

[PATCH] nvme-multipath: require exact iopolicy names for module parameter

[dayou5941]

From: liyouhong <liyouhong@kylinos.cn>

The iopolicy module parameter uses strncmp prefix matching, so values
like "numax" are accepted as "numa".  The per-subsystem sysfs attribute
already requires an exact match via sysfs_streq().  Parse both through
a shared helper so invalid values are rejected consistently.

Signed-off-by: liyouhong <liyouhong@kylinos.cn>
---
 drivers/nvme/host/multipath.c | 40 +++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 263161cb8ac0..ce8dbb741d57 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -73,19 +73,29 @@ static const char *nvme_iopolicy_names[] = {
 
 static int iopolicy = NVME_IOPOLICY_NUMA;
 
+static int nvme_iopolicy_parse(const char *str)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
+		if (sysfs_streq(str, nvme_iopolicy_names[i]))
+			return i;
+	}
+	return -EINVAL;
+}
+
 static int nvme_set_iopolicy(const char *val, const struct kernel_param *kp)
 {
+	int policy;
+
 	if (!val)
 		return -EINVAL;
-	if (!strncmp(val, "numa", 4))
-		iopolicy = NVME_IOPOLICY_NUMA;
-	else if (!strncmp(val, "round-robin", 11))
-		iopolicy = NVME_IOPOLICY_RR;
-	else if (!strncmp(val, "queue-depth", 11))
-		iopolicy = NVME_IOPOLICY_QD;
-	else
-		return -EINVAL;
 
+	policy = nvme_iopolicy_parse(val);
+	if (policy < 0)
+		return policy;
+
+	iopolicy = policy;
 	return 0;
 }
 
@@ -1039,16 +1049,14 @@ static ssize_t nvme_subsys_iopolicy_store(struct device *dev,
 {
 	struct nvme_subsystem *subsys =
 		container_of(dev, struct nvme_subsystem, dev);
-	int i;
+	int policy;
 
-	for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
-		if (sysfs_streq(buf, nvme_iopolicy_names[i])) {
-			nvme_subsys_iopolicy_update(subsys, i);
-			return count;
-		}
-	}
+	policy = nvme_iopolicy_parse(buf);
+	if (policy < 0)
+		return policy;
 
-	return -EINVAL;
+	nvme_subsys_iopolicy_update(subsys, policy);
+	return count;
 }
 SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR,
 		      nvme_subsys_iopolicy_show, nvme_subsys_iopolicy_store);
-- 
2.25.1

Re: [PATCH] nvme-multipath: require exact iopolicy names for module parameter

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] nvme-multipath: require exact iopolicy names for module parameter

[John Garry]

On 29/05/2026 09:51, dayou5941@163.com wrote:
> From: liyouhong <liyouhong@kylinos.cn>
> 
> The iopolicy module parameter uses strncmp prefix matching, so values
> like "numax" are accepted as "numa".  The per-subsystem sysfs attribute
> already requires an exact match via sysfs_streq().  Parse both through
> a shared helper so invalid values are rejected consistently.
> 
> Signed-off-by: liyouhong <liyouhong@kylinos.cn>

Feel free to ignore my comments below, FWIW:

Reviewed-by: John Garry <john.g.garry@oracle.com>

 > --->   drivers/nvme/host/multipath.c | 40 
+++++++++++++++++++++--------------
>   1 file changed, 24 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 263161cb8ac0..ce8dbb741d57 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -73,19 +73,29 @@ static const char *nvme_iopolicy_names[] = {
>   
>   static int iopolicy = NVME_IOPOLICY_NUMA;
>   
> +static int nvme_iopolicy_parse(const char *str)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
> +		if (sysfs_streq(str, nvme_iopolicy_names[i]))
> +			return i;
> +	}
> +	return -EINVAL;

This is nearly duplicating __sysfs_match_string

BTW, going slightly off topic, I think that nvme_iopolicy_names could be 
made const char *const

> +}
> +
>   static int nvme_set_iopolicy(const char *val, const struct kernel_param *kp)
>   {
> +	int policy;
> +
>   	if (!val)
>   		return -EINVAL;
> -	if (!strncmp(val, "numa", 4))
> -		iopolicy = NVME_IOPOLICY_NUMA;
> -	else if (!strncmp(val, "round-robin", 11))
> -		iopolicy = NVME_IOPOLICY_RR;
> -	else if (!strncmp(val, "queue-depth", 11))
> -		iopolicy = NVME_IOPOLICY_QD;
> -	else
> -		return -EINVAL;
>   
> +	policy = nvme_iopolicy_parse(val);
> +	if (policy < 0)
> +		return policy;
> +
> +	iopolicy = policy;
>   	return 0;
>   }
>   
> @@ -1039,16 +1049,14 @@ static ssize_t nvme_subsys_iopolicy_store(struct device *dev,
>   {
>   	struct nvme_subsystem *subsys =
>   		container_of(dev, struct nvme_subsystem, dev);
> -	int i;
> +	int policy;
>   
> -	for (i = 0; i < ARRAY_SIZE(nvme_iopolicy_names); i++) {
> -		if (sysfs_streq(buf, nvme_iopolicy_names[i])) {
> -			nvme_subsys_iopolicy_update(subsys, i);
> -			return count;
> -		}
> -	}
> +	policy = nvme_iopolicy_parse(buf);
> +	if (policy < 0)
> +		return policy;
>   
> -	return -EINVAL;
> +	nvme_subsys_iopolicy_update(subsys, policy);
> +	return count;
>   }
>   SUBSYS_ATTR_RW(iopolicy, S_IRUGO | S_IWUSR,
>   		      nvme_subsys_iopolicy_show, nvme_subsys_iopolicy_store);

Re: [PATCH] nvme-multipath: require exact iopolicy names for module parameter

[Keith Busch]

On Fri, May 29, 2026 at 04:51:43PM +0800, dayou5941@163.com wrote:
> From: liyouhong <liyouhong@kylinos.cn>
> 
> The iopolicy module parameter uses strncmp prefix matching, so values
> like "numax" are accepted as "numa".  The per-subsystem sysfs attribute
> already requires an exact match via sysfs_streq().  Parse both through
> a shared helper so invalid values are rejected consistently.

Thanks, applied to nvme-7.2.