[PATCH 4/6] drm/gem: add functions to get/put pages

[Rob Clark]

On Mon, Sep 12, 2011 at 2:21 PM, Rob Clark <rob.clark at linaro.org> wrote:
> From: Rob Clark <rob at ti.com>
>
> This factors out common code from psb_gtt_attach_pages()/
> i915_gem_object_get_pages_gtt() and psb_gtt_detach_pages()/
> i915_gem_object_put_pages_gtt().
>
> Signed-off-by: Rob Clark <rob at ti.com>
> ---
>  drivers/gpu/drm/drm_gem.c |   68 +++++++++++++++++++++++++++++++++++++++++++++
>  include/drm/drmP.h        |    3 ++
>  2 files changed, 71 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 396e60c..05113c3 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -285,6 +285,74 @@ again:
>  }
>  EXPORT_SYMBOL(drm_gem_handle_create);
>
> +/**
> + * drm_gem_get_pages - helper to allocate backing pages for a GEM object
> + * @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 = obj->filp->f_path.dentry->d_inode;
> +       mapping = inode->i_mapping;
> +
> +       npages = obj->size >> PAGE_SHIFT;
> +
> +       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);

note:  I'll send an updated version of this patch w/ a

  BUG_ON((gfpmask & __GFP_DMA32) && (page_to_pfn(p) >= 0x00100000UL));

or something roughly like this, to catch cases where
shmem_read_mapping_page_gfp() doesn't actually give us a page in the
low 4GB..

It is only a theoretical issue currently, as (AFAIK) no devices w/ 4GB
restriction currently have enough memory to hit this problem.  But it
would be good to have some error checking in case
shmem_read_mapping_page_gfp() isn't fixed by the time we have devices
that would have this problem.

BR,
-R

> +               if (IS_ERR(p))
> +                       goto fail;
> +               pages[i] = p;
> +       }
> +
> +       return pages;
> +
> +fail:
> +       while (i--) {
> +               page_cache_release(pages[i]);
> +       }
> +       drm_free_large(pages);
> +       return ERR_PTR(PTR_ERR(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
> + */
> +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;
> +
> +       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);
>
>  /**
>  * drm_gem_free_mmap_offset - release a fake mmap offset for an object
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 43538b6..a62d8fe 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -1624,6 +1624,9 @@ drm_gem_object_handle_unreference_unlocked(struct drm_gem_object *obj)
>        drm_gem_object_unreference_unlocked(obj);
>  }
>
> +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);
>  void drm_gem_free_mmap_offset(struct drm_gem_object *obj);
>  int drm_gem_create_mmap_offset(struct drm_gem_object *obj);
>
> --
> 1.7.5.4
>
>