On 7/10/2026 10:12 PM, Dan Carpenter wrote:
> On Fri, Jul 10, 2026 at 10:08:11PM +0800, Zhu, Lingshan wrote:
>> On 7/10/2026 9:57 PM, Dan Carpenter wrote:
>>
>>> On Fri, Jul 10, 2026 at 09:47:32PM +0800, Zhu, Lingshan wrote:
>>>> On 7/10/2026 7:29 PM, Srinivasan Shanmugam wrote:
>>>>
>>>>> debugfs is intended for debugging only, and failures to create debugfs
>>>>> entries should not affect normal operation.
>>>>>
>>>>> Remove the check for debugfs_create_dir() in kfd_debugfs_add_process().
>>>>> If debugfs entries cannot be created, continue without them instead of
>>>>> reporting an unnecessary error.
>>>>>
>>>>> Fixes: 22ab1bb3994a ("amdkfd: expose pasid of secondary contexts by
>>>>> debugfs")
>>>>> Reported-by: Dan Carpenter <[email protected]>
>>>>> Cc: Zhu Lingshan <[email protected]>
>>>>> Cc: Felix Kuehling <[email protected]>
>>>>> Signed-off-by: Srinivasan Shanmugam <[email protected]>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c | 4 ----
>>>>> 1 file changed, 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c
>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c
>>>>> index 02673f01b448..7c5bc9c4559a 100644
>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c
>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_debugfs.c
>>>>> @@ -211,10 +211,6 @@ int kfd_debugfs_add_process(struct kfd_process *p)
>>>>> entry->proc_dentry = debugfs_create_dir(name,
>>>>>
>>>>> primary_entry->proc_dentry);
>>>>> }
>>>>> - if (IS_ERR_OR_NULL(entry->proc_dentry)) {
>>>>> - ret = entry->proc_dentry ? PTR_ERR(entry->proc_dentry) :
>>>>> -ENOMEM;
>>>>> - goto err_free_entry;
>>>>> - }
>>>> We need this check because debugfs_create_dir() may fail.
>>>> Removing this check leads to entry leaking when fail.
>>>>
>>> Debugfs functions aren't supposed to be checked. Drivers aren't
>>> supposed to rely on debugfs so it's not required. If debugfs is
>>> failing then you are pretty much screwed anyway.
>>>
>>> I have a blog about the history of this:
>>> https://staticthinking.wordpress.com/2023/07/24/debugfs-functions-are-not-supposed-to-be-checked/
>>>
>>> This code is inside #if defined(CONFIG_DEBUG_FS) so the check
>>> isn't harmful except that it sets a bad example. Back in the day,
>>> this used to be a source of pain for me so Greg made it hard to
>>> write a correct check unless you have the #ifdef. It's to
>>> discourage checking.
>> Thanks Dan for the background, then how do we prevent the entry leaking if
>> we do not check debugfs_create_dir?
> We just don't worry about it. If that happens, you probably are going
> to need to do a kernel upgrade or replace your ram or something. A
> small leak is the least of your worries.
>
> This is the answer that Greg told me back in the day.
Thanks Dan for the information!
>
> regards,
> dan carpenter
>
