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

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

[Adrian Huang12]

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

[Ira Weiny]

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

[Coly Li]

On 2020/9/4 00:06, Ira Weiny wrote:
> 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...

I am not author of c2affe920b0e, but I guess it was because
bdev_dax_supported() needed blocksize, so blocksize should pass previous
checks firstly to make sure bdev_dax_supported() has a correct blocksize
to check.

> 
> As a direct fix to c2affe920b0e
> 
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>

Thanks.

Coly Li


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

[John Pittman]

But it should be moved prior to the two bdev_dax_pgoff() checks right?
 Else a misaligned partition on a dax unsupported block device can
print the below messages.

kernel: sda1: error: unaligned partition for dax
kernel: sda2: error: unaligned partition for dax
kernel: sda3: error: unaligned partition for dax

Reviewed-by: John Pittman <jpittman@redhat.com>

On Thu, Sep 3, 2020 at 12:12 PM Coly Li <colyli@suse.de> wrote:
>
> On 2020/9/4 00:06, Ira Weiny wrote:
> > 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...
>
> I am not author of c2affe920b0e, but I guess it was because
> bdev_dax_supported() needed blocksize, so blocksize should pass previous
> checks firstly to make sure bdev_dax_supported() has a correct blocksize
> to check.
>
> >
> > As a direct fix to c2affe920b0e
> >
> > Reviewed-by: Ira Weiny <ira.weiny@intel.com>
>
> Thanks.
>
> Coly Li
>
>
> >
> >> 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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Re: [PATCH] dax: fix for do not print error message for non-persistent memory block device

[Coly Li]

On 2020/9/11 04:29, John Pittman wrote:
> But it should be moved prior to the two bdev_dax_pgoff() checks right?
>  Else a misaligned partition on a dax unsupported block device can
> print the below messages.
> 
> kernel: sda1: error: unaligned partition for dax
> kernel: sda2: error: unaligned partition for dax
> kernel: sda3: error: unaligned partition for dax
> 

Aha, yes you are right, I agree with you.

Coly Li


> Reviewed-by: John Pittman <jpittman@redhat.com>
> 
> On Thu, Sep 3, 2020 at 12:12 PM Coly Li <colyli@suse.de> wrote:
>>
>> On 2020/9/4 00:06, Ira Weiny wrote:
>>> 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...
>>
>> I am not author of c2affe920b0e, but I guess it was because
>> bdev_dax_supported() needed blocksize, so blocksize should pass previous
>> checks firstly to make sure bdev_dax_supported() has a correct blocksize
>> to check.
>>
>>>
>>> As a direct fix to c2affe920b0e
>>>
>>> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
>>
>> Thanks.
>>
>> Coly Li
>>
[snipped]
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