[PATCH 2/2] nvme: delete disk when last path is gone

[Hannes Reinecke]

On 2/23/21 1:56 PM, Minwoo Im wrote:
> On 21-02-23 12:59:22, Hannes Reinecke wrote:
>> The multipath code currently deletes the disk only after all references
>> to it are dropped rather than when the last path to that disk is lost.
>> This has been reported to cause problems with some use cases like MD RAID.
>>
>> This patch implements an alternative behaviour of deleting the disk when
>> the last path is gone, ie the same behaviour as non-multipathed nvme
>> devices. The new behaviour will be selected with the 'fail_if_no_path'
>> attribute, as returning it's arguably the same functionality.
>>
>> Suggested-by: Keith Busch <kbusch at kernel.org>
>> Signed-off-by: Hannes Reinecke <hare at suse.de>
>> ---
>>  drivers/nvme/host/core.c      |  1 +
>>  drivers/nvme/host/multipath.c |  3 ++-
>>  drivers/nvme/host/nvme.h      | 17 +++++++++++++++--
>>  3 files changed, 18 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 2fb3ecc0c53b..d717a6283d6e 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -542,6 +542,7 @@ static void nvme_free_ns_head(struct kref *ref)
>>  		container_of(ref, struct nvme_ns_head, ref);
>>  
>>  	nvme_mpath_remove_disk(head);
>> +	nvme_mpath_put_disk(head);
>>  	ida_simple_remove(&head->subsys->ns_ida, head->instance);
>>  	cleanup_srcu_struct(&head->srcu);
>>  	nvme_put_subsystem(head->subsys);
>> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
>> index d5773ea105b1..f995b8234622 100644
>> --- a/drivers/nvme/host/multipath.c
>> +++ b/drivers/nvme/host/multipath.c
>> @@ -724,6 +724,8 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
>>  
>>  void nvme_mpath_remove_disk(struct nvme_ns_head *head)
>>  {
>> +	if (test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags))
>> +		return;
>>  	if (!head->disk)
>>  		return;
>>  	if (head->disk->flags & GENHD_FL_UP)
>> @@ -741,7 +743,6 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head)
>>  		 */
>>  		head->disk->queue = NULL;
>>  	}
>> -	put_disk(head->disk);
>>  }
>>  
>>  int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
>> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
>> index 3d2513f8194d..e6efa085f08a 100644
>> --- a/drivers/nvme/host/nvme.h
>> +++ b/drivers/nvme/host/nvme.h
>> @@ -681,8 +681,12 @@ static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
>>  {
>>  	struct nvme_ns_head *head = ns->head;
>>  
>> -	if (head->disk && list_empty(&head->list))
>> -		kblockd_schedule_work(&head->requeue_work);
>> +	if (head->disk && list_empty(&head->list)) {
>> +		if (test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags))
>> +			nvme_mpath_remove_disk(head);
> 
> Does it need to call nvme_mpath_remove_disk here ?  It looks like it
> returns with nothing right away if NVME_NSHEAD_FAIL_IF_NO_PATH is set.
> 
Argl. Yes, you are correct.

I'll be reworking that one.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		           Kernel Storage Architect
hare at suse.de			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
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