Re: [PATCH v3 5/6] drm/gem-shmem: Track folio accessed/dirty status in mmap

[Igor Torrente <igor.torrente@collabora.com>]

Hi Thomas,

On 5/26/26 11:44, Thomas Zimmermann wrote:
> Hi
>
> Am 20.05.26 um 15:11 schrieb Igor Torrente:
> [...]
>>
>> I'm not familiar with the drm_gem, code so I don't any more 
>> insightful information
>> to share.  But hopefully we can find a better fix for this.
>
> Do you have huge pages enabled ?

No, I didn't even compile my kernel with huge pages. I've already been 
burned by that before


BR,
Igor Torrente

>
> Best regards
> Thomas
>
>>
>> BR,
>> Igor Torrente
>>
>>> ---
>>>   drivers/gpu/drm/drm_gem_shmem_helper.c | 20 ++++++++++++++++++++
>>>   1 file changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
>>> b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> index c3a054899ba3..0c86ad40a049 100644
>>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>>> @@ -598,6 +598,9 @@ static vm_fault_t drm_gem_shmem_fault(struct 
>>> vm_fault *vmf)
>>>       if (ret != VM_FAULT_NOPAGE)
>>>           ret = vmf_insert_pfn(vma, vmf->address, pfn);
>>>   +    if (likely(!(ret & VM_FAULT_ERROR)))
>>> +        folio_mark_accessed(folio);
>>> +
>>>   out:
>>>       dma_resv_unlock(obj->resv);
>>>   @@ -638,10 +641,27 @@ static void drm_gem_shmem_vm_close(struct 
>>> vm_area_struct *vma)
>>>       drm_gem_vm_close(vma);
>>>   }
>>>   +static vm_fault_t drm_gem_shmem_pfn_mkwrite(struct vm_fault *vmf)
>>> +{
>>> +    struct vm_area_struct *vma = vmf->vma;
>>> +    struct drm_gem_object *obj = vma->vm_private_data;
>>> +    struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
>>> +    pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page 
>>> offset within VMA */
>>> +    struct page *page = shmem->pages[page_offset];
>>> +    struct folio *folio = page_folio(page);
>>> +
>>> +    file_update_time(vma->vm_file);
>>> +
>>> +    folio_mark_dirty(folio);
>>> +
>>> +    return 0;
>>> +}
>>> +
>>>   const struct vm_operations_struct drm_gem_shmem_vm_ops = {
>>>       .fault = drm_gem_shmem_fault,
>>>       .open = drm_gem_shmem_vm_open,
>>>       .close = drm_gem_shmem_vm_close,
>>> +    .pfn_mkwrite = drm_gem_shmem_pfn_mkwrite,
>>>   };
>>>   EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
>