[dm-devel] [External] [PATCH] dax: fix for do not print error message for non-persistent memory block device

[Adrian Huang12]

> -----Original Message-----
> From: Coly Li <colyli at suse.de>
> Sent: Thursday, September 3, 2020 7:56 PM
> To: linux-nvdimm at lists.01.org
> Cc: dm-devel at redhat.com; Coly Li <colyli at suse.de>; Adrian Huang12
> <ahuang12 at lenovo.com>; Ira Weiny <ira.weiny at intel.com>; Jan Kara
> <jack at suse.com>; Mike Snitzer <snitzer at redhat.com>; Pankaj Gupta
> <pankaj.gupta.linux at gmail.com>; Vishal Verma <vishal.l.verma at intel.com>
> Subject: [External] [PATCH] dax: fix for do not print error message for non-
> persistent memory block device
> 
> 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 at suse.de>

The dax error messages ("dm-X: error: dax access failed (-95)") are gone away when executing the command 'lvm2-testsuite --only activate-minor'.

Reviewed-and-Tested-by: Adrian Huang <ahuang12 at lenovo.com>

> Cc: Adrian Huang <ahuang12 at lenovo.com>
> Cc: Ira Weiny <ira.weiny at intel.com>
> Cc: Jan Kara <jack at suse.com>
> Cc: Mike Snitzer <snitzer at redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux at gmail.com>
> Cc: Vishal Verma <vishal.l.verma at 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