[PATCH 2/5] drm/gem: add shmem get/put page helpers
Daniel Vetter
daniel at ffwll.ch
Mon Jul 8 13:18:47 PDT 2013
On Mon, Jul 08, 2013 at 02:56:31PM -0400, Rob Clark wrote:
> 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..
Would look funny to me to allow it in one place and not in another one.
Maybe just throw a new WARN_ON in here (WARN since it's not fatal)?
-Daniel
>
> 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>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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