[PATCH v2] dax: fix for do not print error message for non-persistent memory block device

[PATCH v2] dax: fix for do not print error message for non-persistent memory block device

[Coly Li]

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>
Reviewed-and-Tested-by: 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>
---
Changelog:
v2: add Reviewed-and-Tested-by from Adrian Huang.
v1: initial version.

 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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Re: [PATCH v2] dax: fix for do not print error message for non-persistent memory block device

[Pankaj Gupta]

> 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>
> Reviewed-and-Tested-by: 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>
> ---
> Changelog:
> v2: add Reviewed-and-Tested-by from Adrian Huang.
> v1: initial version.
>
>  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;
> --

Looks good.
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
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Re: [PATCH v2] dax: fix for do not print error message for non-persistent memory block device

[Mike Snitzer]

On Thu, Sep 03 2020 at 11:28am -0400,
Coly Li <colyli@suse.de> 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)) {

Don't think I've ever seen a one-liner fix document the diff in its
patch header.  Really no need for that.

> Fixes: c2affe920b0e ("dax: do not print error message for non-persistent memory block device")
> Signed-off-by: Coly Li <colyli@suse.de>
> Reviewed-and-Tested-by: 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>

Thanks for fixing this,

Reviewed-by: Mike Snitzer <snitzer@redhat.com>


> ---
> Changelog:
> v2: add Reviewed-and-Tested-by from Adrian Huang.
> v1: initial version.
> 
>  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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Re: [PATCH v2] dax: fix for do not print error message for non-persistent memory block device

[Coly Li]

On 2020/9/4 00:00, Mike Snitzer wrote:
> On Thu, Sep 03 2020 at 11:28am -0400,
> Coly Li <colyli@suse.de> 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)) {
> 
> Don't think I've ever seen a one-liner fix document the diff in its
> patch header.  Really no need for that.
>
Oops, I just see this comment when I maximum my email client window now.
OK, I will post a v4 version to remove the above diff-like style comment.

Coly Li
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