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Subject: Re: [PATCH] nvme-multipath: implement active-active round-robin path
 selector
To:     Baegjae Sung <baegjae@gmail.com>, keith.busch@intel.com,
        axboe@fb.com, hch@lst.de
Cc:     linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20180327043851.6640-1-baegjae@gmail.com>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <6a9c0385-7055-13da-fc5b-f7b7c41cd3eb@grimberg.me>
Date:   Wed, 4 Apr 2018 15:39:02 +0300
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> @@ -85,7 +121,14 @@ static blk_qc_t nvme_ns_head_make_request(struct request_queue *q,
>   	int srcu_idx;
>   
>   	srcu_idx = srcu_read_lock(&head->srcu);
> -	ns = nvme_find_path(head);
> +	switch (head->mpath_policy) {
> +	case NVME_MPATH_ROUND_ROBIN:
> +		ns = nvme_find_path_rr(head);
> +		break;
> +	case NVME_MPATH_ACTIVE_STANDBY:
> +	default:
> +		ns = nvme_find_path(head);
> +	}

If we grow multiple path selectors, would be more elegant to
use a callout mechanism.