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Subject: Re: [PATCH v2] nvme: fix multipath crash when ANA desactivated
To:     Christoph Hellwig <hch@lst.de>
CC:     Marta Rybczynska <mrybczyn@kalray.eu>, <kbusch@kernel.org>,
        <axboe@fb.com>, <sagi@grimberg.me>,
        <linux-nvme@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        Samuel Jones <sjones@kalray.eu>,
        Jean-Baptiste Riaux <jbriaux@kalray.eu>
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From:   Max Gurtovoy <maxg@mellanox.com>
Message-ID: <0d113713-0198-0dc2-2a8f-a9fbcabbf05a@mellanox.com>
Date:   Wed, 10 Jul 2019 11:53:40 +0300
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On 7/10/2019 12:29 AM, Christoph Hellwig wrote:
> On Sat, Jul 06, 2019 at 01:06:44PM +0300, Max Gurtovoy wrote:
>>> +	/* check if multipath is enabled and we have the capability */
>>> +	if (!multipath)
>>> +		return 0;
>>> +	if (!ctrl->subsys || ((ctrl->subsys->cmic & (1 << 3)) != 0))
>> shouldn't it be:
>>
>> if (!ctrl->subsys || ((ctrl->subsys->cmic & (1 << 3)) == 0))
>>
>> or
>>
>> if (!ctrl->subsys || !(ctrl->subsys->cmic & (1 << 3)))
>>
>>
>> Otherwise, you don't really do any initialization and return 0 in case you have the capability, right ?
> Yes.  FYI, my idea how to fix this would be something like:
>
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index a9a927677970..cdb3e5baa329 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -12,11 +12,6 @@ module_param(multipath, bool, 0444);
>   MODULE_PARM_DESC(multipath,
>   	"turn on native support for multiple controllers per subsystem");
>   
> -inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
> -{
> -	return multipath && ctrl->subsys && (ctrl->subsys->cmic & (1 << 3));
> -}
> -
>   /*
>    * If multipathing is enabled we need to always use the subsystem instance
>    * number for numbering our devices to avoid conflicts between subsystems that
> @@ -622,7 +617,7 @@ int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
>   {
>   	int error;
>   
> -	if (!nvme_ctrl_use_ana(ctrl))
> +	if (!multipath || !ctrl->subsys || !(ctrl->subsys->cmic & (1 << 3)))
>   		return 0;
>   
>   	ctrl->anacap = id->anacap;
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 716a876119c8..14eca76bec5c 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -485,7 +485,10 @@ extern const struct attribute_group *nvme_ns_id_attr_groups[];
>   extern const struct block_device_operations nvme_ns_head_ops;
>   
>   #ifdef CONFIG_NVME_MULTIPATH
> -bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl);
> +static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
> +{
> +	return ctrl->ana_log_buf != NULL;
> +}
>   void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
>   			struct nvme_ctrl *ctrl, int *flags);
>   void nvme_failover_req(struct request *req);

Yes this looks good.