[PATCH Review 1/1] drm/ttm: fix debugfs node create failed

[Christian König]

Am 12.10.21 um 15:12 schrieb Das, Nirmoy:
>
> On 10/12/2021 1:58 PM, Stanley.Yang wrote:
>> Test scenario:
>>      modprobe amdgpu -> rmmod amdgpu -> modprobe amdgpu
>> Error log:
>>      [   54.396807] debugfs: File 'page_pool' in directory 'amdttm' 
>> already present!
>>      [   54.396833] debugfs: File 'page_pool_shrink' in directory 
>> 'amdttm' already present!
>>      [   54.396848] debugfs: File 'buffer_objects' in directory 
>> 'amdttm' already present!
>
>
> We should instead add a check if those debugfs files already 
> exist/created in ttm debugfs dir using debugfs_lookup() before creating.

No, IIRC the Intel guys had fixed that already by adding/removing the 
debugfs file on module load/unload.


Christian.

>
>
> Regards,
>
> Nirmoy
>
>
>
>> Reason:
>>      page_pool, page_pool_shrink and buffer_objects can be removed when
>>      rmmod amdttm, in the above test scenario only rmmod amdgpu, so 
>> those
>>      debugfs node will not be removed, this caused file create failed.
>> Soultion:
>>      create ttm_page directory under ttm_root directory when insmod 
>> amdgpu,
>>      page_pool, page_pool_shrink and buffer_objects are stored in 
>> ttm_page directiry,
>>      remove ttm_page directory when do rmmod amdgpu, this can fix 
>> above issue.
>>
>> Signed-off-by: Stanley.Yang <Stanley.Yang at amd.com>
>> ---
>>   drivers/gpu/drm/ttm/ttm_device.c | 12 +++++++++++-
>>   drivers/gpu/drm/ttm/ttm_module.c |  1 +
>>   drivers/gpu/drm/ttm/ttm_module.h |  1 +
>>   drivers/gpu/drm/ttm/ttm_pool.c   |  4 ++--
>>   4 files changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_device.c 
>> b/drivers/gpu/drm/ttm/ttm_device.c
>> index 1de23edbc182..ad170328f0c8 100644
>> --- a/drivers/gpu/drm/ttm/ttm_device.c
>> +++ b/drivers/gpu/drm/ttm/ttm_device.c
>> @@ -55,6 +55,10 @@ static void ttm_global_release(void)
>>         ttm_pool_mgr_fini();
>>   +#ifdef CONFIG_DEBUG_FS
>> +    debugfs_remove(ttm_debugfs_page);
>> +#endif
>> +
>>       __free_page(glob->dummy_read_page);
>>       memset(glob, 0, sizeof(*glob));
>>   out:
>> @@ -85,6 +89,10 @@ static int ttm_global_init(void)
>>           >> PAGE_SHIFT;
>>       num_dma32 = min(num_dma32, 2UL << (30 - PAGE_SHIFT));
>>   +#ifdef CONFIG_DEBUG_FS
>> +    ttm_debugfs_page = debugfs_create_dir("ttm_page", 
>> ttm_debugfs_root);
>> +#endif
>> +
>>       ttm_pool_mgr_init(num_pages);
>>       ttm_tt_mgr_init(num_pages, num_dma32);
>>   @@ -98,8 +106,10 @@ static int ttm_global_init(void)
>>       INIT_LIST_HEAD(&glob->device_list);
>>       atomic_set(&glob->bo_count, 0);
>>   -    debugfs_create_atomic_t("buffer_objects", 0444, ttm_debugfs_root,
>> +#ifdef CONFIG_DEBUG_FS
>> +    debugfs_create_atomic_t("buffer_objects", 0444, ttm_debugfs_page,
>>                   &glob->bo_count);
>> +#endif
>>   out:
>>       mutex_unlock(&ttm_global_mutex);
>>       return ret;
>> diff --git a/drivers/gpu/drm/ttm/ttm_module.c 
>> b/drivers/gpu/drm/ttm/ttm_module.c
>> index 88970a6b8e32..66595e6e7087 100644
>> --- a/drivers/gpu/drm/ttm/ttm_module.c
>> +++ b/drivers/gpu/drm/ttm/ttm_module.c
>> @@ -38,6 +38,7 @@
>>   #include "ttm_module.h"
>>     struct dentry *ttm_debugfs_root;
>> +struct dentry *ttm_debugfs_page;
>>     static int __init ttm_init(void)
>>   {
>> diff --git a/drivers/gpu/drm/ttm/ttm_module.h 
>> b/drivers/gpu/drm/ttm/ttm_module.h
>> index d7cac5d4b835..6007dc66f44e 100644
>> --- a/drivers/gpu/drm/ttm/ttm_module.h
>> +++ b/drivers/gpu/drm/ttm/ttm_module.h
>> @@ -36,5 +36,6 @@
>>   struct dentry;
>>     extern struct dentry *ttm_debugfs_root;
>> +extern struct dentry *ttm_debugfs_page;
>>     #endif /* _TTM_MODULE_H_ */
>> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c 
>> b/drivers/gpu/drm/ttm/ttm_pool.c
>> index 8be7fd7161fd..ecb33daad7b5 100644
>> --- a/drivers/gpu/drm/ttm/ttm_pool.c
>> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
>> @@ -709,9 +709,9 @@ int ttm_pool_mgr_init(unsigned long num_pages)
>>       }
>>     #ifdef CONFIG_DEBUG_FS
>> -    debugfs_create_file("page_pool", 0444, ttm_debugfs_root, NULL,
>> +    debugfs_create_file("page_pool", 0444, ttm_debugfs_page, NULL,
>>                   &ttm_pool_debugfs_globals_fops);
>> -    debugfs_create_file("page_pool_shrink", 0400, ttm_debugfs_root, 
>> NULL,
>> +    debugfs_create_file("page_pool_shrink", 0400, ttm_debugfs_page, 
>> NULL,
>>                   &ttm_pool_debugfs_shrink_fops);
>>   #endif