[PATCH 2/5] drm/gem: add shmem get/put page helpers

[Rob Clark]

On Mon, Jul 8, 2013 at 4:45 AM, Patrik Jakobsson
<patrik.r.jakobsson at gmail.com> wrote:
> On Sun, Jul 7, 2013 at 8:58 PM, Rob Clark <robdclark at gmail.com> wrote:
>> Basically just extracting some code duplicated in gma500, omapdrm, udl,
>> and upcoming msm driver.
>>
>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>> ---
>>  drivers/gpu/drm/drm_gem.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
>>  include/drm/drmP.h        |  4 +++
>>  2 files changed, 95 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
>> index 443eeff..853dea6 100644
>> --- a/drivers/gpu/drm/drm_gem.c
>> +++ b/drivers/gpu/drm/drm_gem.c
>> @@ -406,6 +406,97 @@ int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
>>  }
>>  EXPORT_SYMBOL(drm_gem_create_mmap_offset);
>>
>> +/**
>> + * drm_gem_get_pages - helper to allocate backing pages for a GEM object
>> + * from shmem
>> + * @obj: obj in question
>> + * @gfpmask: gfp mask of requested pages
>> + */
>> +struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask)
>> +{
>> +       struct inode *inode;
>> +       struct address_space *mapping;
>> +       struct page *p, **pages;
>> +       int i, npages;
>> +
>> +       /* This is the shared memory object that backs the GEM resource */
>> +       inode = file_inode(obj->filp);
>> +       mapping = inode->i_mapping;
>> +
>> +       npages = obj->size >> PAGE_SHIFT;
>
> Theoretical issue, but what if obj->size is not page aligned? Perhaps put a
> roundup(obj->size, PAGE_SIZE) here?

so, drm_gem_object_init() does have:

	BUG_ON((size & (PAGE_SIZE - 1)) != 0);

so I was kinda assuming that we can count on the size already being
aligned.  But I guess in case someone somehow bypasses
drm_gem_object_init() it wouldn't hurt to round up the size..

BR,
-R

>> +
>> +       pages = drm_malloc_ab(npages, sizeof(struct page *));
>> +       if (pages == NULL)
>> +               return ERR_PTR(-ENOMEM);
>> +
>> +       gfpmask |= mapping_gfp_mask(mapping);
>> +
>> +       for (i = 0; i < npages; i++) {
>> +               p = shmem_read_mapping_page_gfp(mapping, i, gfpmask);
>> +               if (IS_ERR(p))
>> +                       goto fail;
>> +               pages[i] = p;
>> +
>> +               /* There is a hypothetical issue w/ drivers that require
>> +                * buffer memory in the low 4GB.. if the pages are un-
>> +                * pinned, and swapped out, they can end up swapped back
>> +                * in above 4GB.  If pages are already in memory, then
>> +                * shmem_read_mapping_page_gfp will ignore the gfpmask,
>> +                * even if the already in-memory page disobeys the mask.
>> +                *
>> +                * It is only a theoretical issue today, because none of
>> +                * the devices with this limitation can be populated with
>> +                * enough memory to trigger the issue.  But this BUG_ON()
>> +                * is here as a reminder in case the problem with
>> +                * shmem_read_mapping_page_gfp() isn't solved by the time
>> +                * it does become a real issue.
>> +                *
>> +                * See this thread: http://lkml.org/lkml/2011/7/11/238
>> +                */
>> +               BUG_ON((gfpmask & __GFP_DMA32) &&
>> +                               (page_to_pfn(p) >= 0x00100000UL));
>> +       }
>> +
>> +       return pages;
>> +
>> +fail:
>> +       while (i--)
>> +               page_cache_release(pages[i]);
>> +
>> +       drm_free_large(pages);
>> +       return ERR_CAST(p);
>> +}
>> +EXPORT_SYMBOL(drm_gem_get_pages);
>> +
>> +/**
>> + * drm_gem_put_pages - helper to free backing pages for a GEM object
>> + * @obj: obj in question
>> + * @pages: pages to free
>> + * @dirty: if true, pages will be marked as dirty
>> + * @accessed: if true, the pages will be marked as accessed
>> + */
>> +void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
>> +               bool dirty, bool accessed)
>> +{
>> +       int i, npages;
>> +
>> +       npages = obj->size >> PAGE_SHIFT;
>
> Same thing here.
>
>> +
>> +       for (i = 0; i < npages; i++) {
>> +               if (dirty)
>> +                       set_page_dirty(pages[i]);
>> +
>> +               if (accessed)
>> +                       mark_page_accessed(pages[i]);
>> +
>> +               /* Undo the reference we took when populating the table */
>> +               page_cache_release(pages[i]);
>> +       }
>> +
>> +       drm_free_large(pages);
>> +}
>> +EXPORT_SYMBOL(drm_gem_put_pages);
>> +
>>  /** Returns a reference to the object named by the handle. */
>>  struct drm_gem_object *
>>  drm_gem_object_lookup(struct drm_device *dev, struct drm_file *filp,
>> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
>> index 3cb1672..7ec3fa4 100644
>> --- a/include/drm/drmP.h
>> +++ b/include/drm/drmP.h
>> @@ -1730,6 +1730,10 @@ void drm_gem_free_mmap_offset(struct drm_gem_object *obj);
>>  int drm_gem_create_mmap_offset(struct drm_gem_object *obj);
>>  int drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size);
>>
>> +struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask);
>> +void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
>> +               bool dirty, bool accessed);
>> +
>>  struct drm_gem_object *drm_gem_object_lookup(struct drm_device *dev,
>>                                              struct drm_file *filp,
>>                                              u32 handle);
>> --
>> 1.8.1.4
>
> Looks good otherwise, so for all 5 patches:
> Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson at gmail.com>