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From: Ira Weiny <ira.weiny@intel.com>
To: Coly Li <colyli@suse.de>
Cc: linux-nvdimm@lists.01.org, dm-devel@redhat.com,
	Adrian Huang <ahuang12@lenovo.com>, Jan Kara <jack@suse.com>,
	Mike Snitzer <snitzer@redhat.com>,
	Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Subject: Re: [PATCH] dax: fix for do not print error message for non-persistent memory block device
Date: Thu, 3 Sep 2020 09:06:08 -0700
Message-ID: <20200903160608.GU878166@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200903115549.17845-1-colyli@suse.de>

On Thu, Sep 03, 2020 at 07:55:49PM +0800, Coly Li wrote:
> When calling __generic_fsdax_supported(), a dax-unsupported device may
> not have dax_dev as NULL, e.g. the dax related code block is not enabled
> by Kconfig.
> 
> Therefore in __generic_fsdax_supported(), to check whether a device
> supports DAX or not, the following order should be performed,
> - If dax_dev pointer is NULL, it means the device driver explicitly
>   announce it doesn't support DAX. Then it is OK to directly return
>   false from __generic_fsdax_supported().
> - If dax_dev pointer is NOT NULL, it might be because the driver doesn't
>   support DAX and not explicitly initialize related data structure. Then
>   bdev_dax_supported() should be called for further check.
> 
> IMHO if device driver desn't explicitly set its dax_dev pointer to NULL,
> this is not a bug. Calling bdev_dax_supported() makes sure they can be
> recognized as dax-unsupported eventually.
> 
> This patch does the following change for the above purpose,
>     -       if (!dax_dev && !bdev_dax_supported(bdev, blocksize)) {
>     +       if (!dax_dev || !bdev_dax_supported(bdev, blocksize)) {
> 
> 
> Fixes: c2affe920b0e ("dax: do not print error message for non-persistent memory block device")
> Signed-off-by: Coly Li <colyli@suse.de>

I hate to do this because I realize this is a bug which people really need
fixed.

However, shouldn't we also check (!dax_dev || !bdev_dax_supported()) as the
_first_ check in __generic_fsdax_supported()?

It seems like the other pr_info's could also be called when DAX is not
supported and we probably don't want them to be?

Perhaps that should be a follow on patch though.  So...

As a direct fix to c2affe920b0e

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> Cc: Adrian Huang <ahuang12@lenovo.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: Jan Kara <jack@suse.com>
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Vishal Verma <vishal.l.verma@intel.com>
> ---
>  drivers/dax/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 32642634c1bb..e5767c83ea23 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -100,7 +100,7 @@ bool __generic_fsdax_supported(struct dax_device *dax_dev,
>  		return false;
>  	}
>  
> -	if (!dax_dev && !bdev_dax_supported(bdev, blocksize)) {
> +	if (!dax_dev || !bdev_dax_supported(bdev, blocksize)) {
>  		pr_debug("%s: error: dax unsupported by block device\n",
>  				bdevname(bdev, buf));
>  		return false;
> -- 
> 2.26.2
> 
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  parent reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03 11:55 Coly Li
2020-09-03 15:26 ` [External] " Adrian Huang12
2020-09-03 16:06 ` Ira Weiny [this message]
2020-09-03 16:12   ` Coly Li
2020-09-10 20:29     ` John Pittman
2020-09-11  0:54       ` Coly Li

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