Re: [PATCH v2] nvme: invalidate paths during rescan

[Sagi Grimberg <sagi@grimberg.me>]

On 7/30/21 12:10 AM, Daniel Wagner wrote:
> From: Hannes Reinecke <hare@suse.de>
> 
> When triggering a rescan due to a namespace resize we will be
> receiving AENs on every controller, triggering a rescan of all
> attached namespaces. If multipath is active only the current path and
> the ns_head disk will be updated, the other paths will still refer to
> the old size until AENs for the remaining controllers are received.
> 
> If I/O comes in before that it might be routed to one of the old
> paths, triggering an I/O failure with 'access beyond end of device'.
> With this patch the old paths are skipped from multipath path
> selection until the controller serving these paths has been rescanned.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> Tested-by: Daniel Wagner <dwagner@suse.de>
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
> v2:
>    - removed churn from failed rebase.
> v1:
>    - https://lore.kernel.org/linux-nvme/20210729194630.i5mhvvgb73duojqq@beryllium.lan/
> 
>   drivers/nvme/host/core.c      |  2 ++
>   drivers/nvme/host/multipath.c | 16 ++++++++++++++++
>   drivers/nvme/host/nvme.h      |  5 +++++
>   3 files changed, 23 insertions(+)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index dfd9dec0c1f6..20a079083129 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1877,6 +1877,7 @@ static int nvme_update_ns_info(struct nvme_ns *ns, struct nvme_id_ns *id)
>   			goto out_unfreeze;
>   	}
>   
> +	clear_bit(NVME_NS_INVALIDATED, &ns->flags);
>   	blk_mq_unfreeze_queue(ns->disk->queue);
>   
>   	if (blk_queue_is_zoned(ns->queue)) {
> @@ -1888,6 +1889,7 @@ static int nvme_update_ns_info(struct nvme_ns *ns, struct nvme_id_ns *id)
>   	if (nvme_ns_head_multipath(ns->head)) {
>   		blk_mq_freeze_queue(ns->head->disk->queue);
>   		nvme_update_disk_info(ns->head->disk, ns, id);
> +		nvme_mpath_invalidate_paths(ns);
>   		blk_stack_limits(&ns->head->disk->queue->limits,
>   				 &ns->queue->limits, 0);
>   		blk_queue_update_readahead(ns->head->disk->queue);
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 3f32c5e86bfc..579020ae058d 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -147,6 +147,21 @@ void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl)
>   	mutex_unlock(&ctrl->scan_lock);
>   }
>   
> +void nvme_mpath_invalidate_paths(struct nvme_ns *ns)

invalidate is not a great name for this very specific case here.

> +{
> +	struct nvme_ns_head *head = ns->head;
> +	sector_t capacity = get_capacity(head->disk);
> +	int node;
> +
> +	for_each_node(node)
> +		rcu_assign_pointer(head->current_path[node], NULL);

Here the ns can get re-selected as the current path.

> +
> +	list_for_each_entry_rcu(ns, &head->list, siblings) {
> +		if (capacity != get_capacity(ns->disk))
> +			set_bit(NVME_NS_INVALIDATED, &ns->flags);

maybe instead of invalidated reverse the polarity with
NVME_NS_READY? clear it here and set it in update_ns_info?

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