[PATCH v2 03/10] nvme-multipath: add error handling support for add_disk()

Luis Chamberlain posted 10 patches 3 years, 2 months ago
[PATCH v2 03/10] nvme-multipath: add error handling support for add_disk()
Posted by Luis Chamberlain 3 years, 2 months ago
We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling.

Since we now can tell for sure when a disk was added, move
setting the bit NVME_NSHEAD_DISK_LIVE only when we did
add the disk successfully.

Nothing to do here as the cleanup is done elsewhere. We take
care and use test_and_set_bit() because it is protects against
two nvme paths simultaneously calling device_add_disk() on the
same namespace head.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 drivers/nvme/host/multipath.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index e8ccdd398f78..35cace4f3f5f 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -496,13 +496,22 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
 static void nvme_mpath_set_live(struct nvme_ns *ns)
 {
 	struct nvme_ns_head *head = ns->head;
+	int rc;
 
 	if (!head->disk)
 		return;
 
+	/*
+	 * test_and_set_bit() is used because it is protecting against two nvme
+	 * paths simultaneously calling device_add_disk() on the same namespace
+	 * head.
+	 */
 	if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
-		device_add_disk(&head->subsys->dev, head->disk,
-				nvme_ns_id_attr_groups);
+		rc = device_add_disk(&head->subsys->dev, head->disk,
+				     nvme_ns_id_attr_groups);
+		if (rc)
+			return;
+		set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);
 		nvme_add_ns_head_cdev(head);
 	}
 
-- 
2.30.2


Re: [PATCH v2 03/10] nvme-multipath: add error handling support for add_disk()
Posted by Keith Busch 3 years, 2 months ago
On Mon, Sep 27, 2021 at 03:00:32PM -0700, Luis Chamberlain wrote:
> +	/*
> +	 * test_and_set_bit() is used because it is protecting against two nvme
> +	 * paths simultaneously calling device_add_disk() on the same namespace
> +	 * head.
> +	 */
>  	if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
> -		device_add_disk(&head->subsys->dev, head->disk,
> -				nvme_ns_id_attr_groups);
> +		rc = device_add_disk(&head->subsys->dev, head->disk,
> +				     nvme_ns_id_attr_groups);
> +		if (rc)
> +			return;
> +		set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);

No need to set_bit() here since the test_and_set_bit() already took care
of that.

Re: [PATCH v2 03/10] nvme-multipath: add error handling support for add_disk()
Posted by Hannes Reinecke 3 years, 2 months ago
On 9/28/21 12:00 AM, Luis Chamberlain wrote:
> We never checked for errors on add_disk() as this function
> returned void. Now that this is fixed, use the shiny new
> error handling.
> 
> Since we now can tell for sure when a disk was added, move
> setting the bit NVME_NSHEAD_DISK_LIVE only when we did
> add the disk successfully.
> 
> Nothing to do here as the cleanup is done elsewhere. We take
> care and use test_and_set_bit() because it is protects against
> two nvme paths simultaneously calling device_add_disk() on the
> same namespace head.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>   drivers/nvme/host/multipath.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index e8ccdd398f78..35cace4f3f5f 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -496,13 +496,22 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
>   static void nvme_mpath_set_live(struct nvme_ns *ns)
>   {
>   	struct nvme_ns_head *head = ns->head;
> +	int rc;
>   
>   	if (!head->disk)
>   		return;
>   
> +	/*
> +	 * test_and_set_bit() is used because it is protecting against two nvme
> +	 * paths simultaneously calling device_add_disk() on the same namespace
> +	 * head.
> +	 */
>   	if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
> -		device_add_disk(&head->subsys->dev, head->disk,
> -				nvme_ns_id_attr_groups);
> +		rc = device_add_disk(&head->subsys->dev, head->disk,
> +				     nvme_ns_id_attr_groups);
> +		if (rc)
> +			return;
> +		set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);
>   		nvme_add_ns_head_cdev(head);
>   	}
>   
> Errm.
Setting the same bit twice?
And shouldn't you unset the bit if 'device_add_disk()' fails?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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