From: Hannes Reinecke <hare@suse.de>
To: Chao Leng <lengchao@huawei.com>, Daniel Wagner <dwagner@suse.de>
Cc: Sagi Grimberg <sagi@grimberg.me>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
Jens Axboe <axboe@fb.com>, Keith Busch <kbusch@kernel.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2] nvme-multipath: Early exit if no path is available
Date: Thu, 28 Jan 2021 10:23:42 +0100 [thread overview]
Message-ID: <8704038d-0b71-5c9c-2d2b-a9ff2166dbe4@suse.de> (raw)
In-Reply-To: <69575290-200e-b4a1-4269-c71e4c2cc37b@huawei.com>
On 1/28/21 10:18 AM, Chao Leng wrote:
>
>
> On 2021/1/28 15:58, Daniel Wagner wrote:
>> On Thu, Jan 28, 2021 at 09:31:30AM +0800, Chao Leng wrote:
>>>> --- 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".
>>
>> The problem is when we enter nvme_round_robin_path() and there is no
>> path available. In this case the initialization ns = nvme_next_ns(head,
>> old) could return a NULL pointer."old" should not be NULL, so there is
>> at least one path that is "old".
> It is impossible to return NULL for nvme_next_ns(head, old).
No. list_next_or_null_rcu()/list_first_or_null_rcu() will return NULL
when then end of the list is reached.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
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next prev parent reply other threads:[~2021-01-28 9:23 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 10:30 [PATCH v2] nvme-multipath: Early exit if no path is available Daniel Wagner
2021-01-27 10:34 ` Hannes Reinecke
2021-01-27 16:49 ` Christoph Hellwig
2021-01-28 1:31 ` Chao Leng
2021-01-28 7:58 ` Daniel Wagner
2021-01-28 9:18 ` Chao Leng
2021-01-28 9:23 ` Hannes Reinecke [this message]
2021-01-29 1:18 ` Chao Leng
2021-01-28 9:40 ` Daniel Wagner
2021-01-29 1:23 ` Chao Leng
2021-01-29 1:42 ` Sagi Grimberg
2021-01-29 3:07 ` Chao Leng
2021-01-29 3:30 ` Sagi Grimberg
2021-01-29 3:36 ` Chao Leng
2021-01-29 7:06 ` Hannes Reinecke
2021-01-29 7:45 ` Chao Leng
2021-01-29 8:33 ` Hannes Reinecke
2021-01-29 8:46 ` Chao Leng
2021-01-29 9:20 ` Hannes Reinecke
2021-02-01 2:16 ` Chao Leng
2021-02-01 7:29 ` Hannes Reinecke
2021-02-01 8:47 ` Chao Leng
2021-02-01 8:57 ` Hannes Reinecke
2021-02-01 9:40 ` Chao Leng
2021-02-01 10:45 ` Hannes Reinecke
2021-02-02 1:12 ` Chao Leng
2021-01-28 1:36 ` Chao Leng
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