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

[Rob Clark]

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 |   87 +++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drmP.h        |    3 ++
 2 files changed, 90 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 396e60c..821ba8a 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -285,6 +285,93 @@ 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);
+		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_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