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Subject: Re: [PATCH v2] nvme-multipath: Early exit if no path is available
To:     Daniel Wagner <dwagner@suse.de>, <linux-nvme@lists.infradead.org>
CC:     Sagi Grimberg <sagi@grimberg.me>, <linux-kernel@vger.kernel.org>,
        "Jens Axboe" <axboe@fb.com>, Hannes Reinecke <hare@suse.de>,
        Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>
References: <20210127103033.15318-1-dwagner@suse.de>
From:   Chao Leng <lengchao@huawei.com>
Message-ID: <db9baae0-547c-7ff4-8b2c-0b95f14be67c@huawei.com>
Date:   Thu, 28 Jan 2021 09:31:30 +0800
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On 2021/1/27 18:30, Daniel Wagner wrote:
> nvme_round_robin_path() should test if the return ns pointer is
> valid. nvme_next_ns() will return a NULL pointer if there is no path
> left.
> 
> Fixes: 75c10e732724 ("nvme-multipath: round-robin I/O policy")
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
> v2:
>    - moved NULL test into the if conditional statement
>    - added Fixes tag
> 
>   drivers/nvme/host/multipath.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 9ac762b28811..282b7a4ea9a9 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -221,7 +221,7 @@ static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
>   	}
>   
>   	for (ns = nvme_next_ns(head, old);
> -	     ns != old;
> +	     ns && ns != old;
nvme_round_robin_path just be called when !"old".
nvme_next_ns should not return NULL when !"old".
It seems unnecessary to add checking "ns".
Is there a bug that "old" in not in "head" list?
If yes, we should fix it.
>   	     ns = nvme_next_ns(head, ns)) {
>   		if (nvme_path_is_disabled(ns))
>   			continue;
>