[dm-devel] [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 at 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