linux-kernel - Re: [PATCH 2/2] libnvdimm/security: ensure sysfs poll thread woke up and fetch updated attr

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Date:   Mon, 3 Aug 2020 13:42:08 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Jane Chu <jane.chu@...cle.com>, dan.j.williams@...el.com,
        vishal.l.verma@...el.com, ira.weiny@...el.com, jmoyer@...hat.com,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] libnvdimm/security: ensure sysfs poll thread woke up
 and fetch updated attr



On 7/24/2020 9:09 AM, Jane Chu wrote:
> commit 7d988097c546 ("acpi/nfit, libnvdimm/security: Add security DSM overwrite support")
> adds a sysfs_notify_dirent() to wake up userspace poll thread when the "overwrite"
> operation has completed. But the notification is issued before the internal
> dimm security state and flags have been updated, so the userspace poll thread
> wakes up and fetches the not-yet-updated attr and falls back to sleep, forever.
> But if user from another terminal issue "ndctl wait-overwrite nmemX" again,
> the command returns instantly.
> 
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Fixes: 7d988097c546 ("acpi/nfit, libnvdimm/security: Add security DSM overwrite support")
> Signed-off-by: Jane Chu <jane.chu@...cle.com>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> ---
>   drivers/nvdimm/security.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvdimm/security.c b/drivers/nvdimm/security.c
> index 8f3971c..4b80150 100644
> --- a/drivers/nvdimm/security.c
> +++ b/drivers/nvdimm/security.c
> @@ -450,14 +450,19 @@ void __nvdimm_security_overwrite_query(struct nvdimm *nvdimm)
>   	else
>   		dev_dbg(&nvdimm->dev, "overwrite completed\n");
>   
> -	if (nvdimm->sec.overwrite_state)
> -		sysfs_notify_dirent(nvdimm->sec.overwrite_state);
> +	/*
> +	 * Mark the overwrite work done and update dimm security flags,
> +	 * then send a sysfs event notification to wake up userspace
> +	 * poll threads to picked up the changed state.
> +	 */
>   	nvdimm->sec.overwrite_tmo = 0;
>   	clear_bit(NDD_SECURITY_OVERWRITE, &nvdimm->flags);
>   	clear_bit(NDD_WORK_PENDING, &nvdimm->flags);
> -	put_device(&nvdimm->dev);
>   	nvdimm->sec.flags = nvdimm_security_flags(nvdimm, NVDIMM_USER);
>   	nvdimm->sec.ext_flags = nvdimm_security_flags(nvdimm, NVDIMM_MASTER);
> +	if (nvdimm->sec.overwrite_state)
> +		sysfs_notify_dirent(nvdimm->sec.overwrite_state);
> +	put_device(&nvdimm->dev);
>   }
>   
>   void nvdimm_security_overwrite_query(struct work_struct *work)
>