Re: [PATCH v4 1/2] nvme-multipath: fix path state evaluation for failfast and ANA

[Hannes Reinecke <hare@suse.de>]

On 10/1/26 11:48 AM, Krishna Iyer wrote:
> nvme_available_path() has two problems that keep I/O queued when it
> should be failed:
> 
> 1. When fast_io_fail_tmo expires, NVME_CTRL_FAILFAST_EXPIRED is set and
>     the path is skipped, but the function still falls through to
>     nvme_mpath_queue_if_no_path(). If delayed_removal_secs is configured
>     the I/O is requeued indefinitely, defeating fast_io_fail_tmo. Only
>     fall through to queue_if_no_path when there really are no paths;
>     if a path exists but its failfast timer has expired, fail instead.
> 
> 2. A LIVE controller counts as a usable path regardless of the namespace
>     ANA state. A path whose ANA state is inaccessible or persistent-loss
>     cannot serve I/O, so it should not count as available. ANA change is
>     transient and bounded by ANATT, so keep queueing while it resolves.
> 
> Also kick the requeue work from nvme_update_ns_ana_state() when a path
> does not transition to live, so parked I/O is re-evaluated when an ANA
> transition leaves the namespace inaccessible.
> 
> Move nvme_state_is_live() above nvme_available_path() so it can be used
> there.
> 
> Assisted-by: Claude:claude-fable-5
> Signed-off-by: Krishna Iyer <kiyer@crusoe.ai>
> ---
>   drivers/nvme/host/multipath.c | 26 +++++++++++++++++++-------
>   1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 11871f5f18c2..0d6c05f0808b 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -509,9 +509,15 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
>   	}
>   }
>   
> +static inline bool nvme_state_is_live(enum nvme_ana_state state)
> +{
> +	return state == NVME_ANA_OPTIMIZED || state == NVME_ANA_NONOPTIMIZED;
> +}
> +
>   static bool nvme_available_path(struct nvme_ns_head *head)
>   	__must_hold_shared(&head->srcu)
>   {
> +	bool failfast = false;
>   	struct nvme_ns *ns;
>   
>   	if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags))
> @@ -519,10 +525,16 @@ static bool nvme_available_path(struct nvme_ns_head *head)
>   
>   	list_for_each_entry_srcu(ns, &head->list, siblings,
>   				 srcu_read_lock_held(&head->srcu)) {
> -		if (test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ns->ctrl->flags))
> +		if (test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ns->ctrl->flags)) {
> +			failfast = true;
>   			continue;
> +		}
>   		switch (nvme_ctrl_state(ns->ctrl)) {
>   		case NVME_CTRL_LIVE:
> +			if (!nvme_state_is_live(ns->ana_state) &&
> +			    ns->ana_state != NVME_ANA_CHANGE)
> +				continue;
> +			return true;
>   		case NVME_CTRL_RESETTING:
>   		case NVME_CTRL_CONNECTING:
>   			return true;
> @@ -531,6 +543,9 @@ static bool nvme_available_path(struct nvme_ns_head *head)
>   		}
>   	}
>   
> +	if (failfast)
> +		return false;
> +
>   	/*
>   	 * If "head->delayed_removal_secs" is configured (i.e., non-zero), do
>   	 * not immediately fail I/O. Instead, requeue the I/O for the configured
> @@ -887,11 +902,6 @@ static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
>   	return 0;
>   }
>   
> -static inline bool nvme_state_is_live(enum nvme_ana_state state)
> -{
> -	return state == NVME_ANA_OPTIMIZED || state == NVME_ANA_NONOPTIMIZED;
> -}
> -
>   static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
>   		struct nvme_ns *ns)
>   {
> @@ -926,8 +936,10 @@ static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
>   		 * is not live but still create the sysfs link to this path from
>   		 * head node if head node of the path has already come alive.
>   		 */
> -		if (test_bit(NVME_NSHEAD_DISK_LIVE, &ns->head->flags))
> +		if (test_bit(NVME_NSHEAD_DISK_LIVE, &ns->head->flags)) {
>   			nvme_mpath_add_sysfs_link(ns->head);
> +			kblockd_schedule_work(&ns->head->requeue_work);
> +		}
>   	}
>   }
>   
Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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