Commit f60d7f0c authored by Chris Wilson's avatar Chris Wilson Committed by Daniel Vetter
Browse files

drm/i915: Pin backing pages for pread 



By using the recently introduced pinning of pages, we can safely drop
the mutex in the knowledge that the pages are not going to disappear
beneath us, and so we can simplify the code for iterating over the pages.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarBen Widawsky <ben@bwidawsk.net>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 755d2218

drivers/gpu/drm/i915/i915_gem.c

+13 −23
Original line number Diff line number Diff line
@@ -343,7 +343,7 @@ shmem_pread_fast(struct page *page, int shmem_page_offset, int page_length, 
				      page_length);

	kunmap_atomic(vaddr);



	return ret;

	return ret ? -EFAULT : 0;

}



static void
@@ -394,7 +394,7 @@ shmem_pread_slow(struct page *page, int shmem_page_offset, int page_length, 
				     page_length);

	kunmap(page);



	return ret;

	return ret ? - EFAULT : 0;

}



static int
@@ -403,7 +403,6 @@ i915_gem_shmem_pread(struct drm_device *dev, 
		     struct drm_i915_gem_pread *args,

		     struct drm_file *file)

{

	struct address_space *mapping = obj->base.filp->f_path.dentry->d_inode->i_mapping;

	char __user *user_data;

	ssize_t remain;

	loff_t offset;
@@ -412,7 +411,6 @@ i915_gem_shmem_pread(struct drm_device *dev, 
	int hit_slowpath = 0;

	int prefaulted = 0;

	int needs_clflush = 0;

	int release_page;



	user_data = (char __user *) (uintptr_t) args->data_ptr;

	remain = args->size;
@@ -433,6 +431,12 @@ i915_gem_shmem_pread(struct drm_device *dev, 
		}

	}



	ret = i915_gem_object_get_pages(obj);

	if (ret)

		return ret;



	i915_gem_object_pin_pages(obj);



	offset = args->offset;



	while (remain > 0) {
@@ -448,18 +452,7 @@ i915_gem_shmem_pread(struct drm_device *dev, 
		if ((shmem_page_offset + page_length) > PAGE_SIZE)

			page_length = PAGE_SIZE - shmem_page_offset;



		if (obj->pages) {

		page = obj->pages[offset >> PAGE_SHIFT];

			release_page = 0;

		} else {

			page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);

			if (IS_ERR(page)) {

				ret = PTR_ERR(page);

				goto out;

			}

			release_page = 1;

		}



		page_do_bit17_swizzling = obj_do_bit17_swizzling &&

			(page_to_phys(page) & (1 << 17)) != 0;
@@ -470,7 +463,6 @@ i915_gem_shmem_pread(struct drm_device *dev, 
			goto next_page;



		hit_slowpath = 1;

		page_cache_get(page);

		mutex_unlock(&dev->struct_mutex);



		if (!prefaulted) {
@@ -488,16 +480,12 @@ i915_gem_shmem_pread(struct drm_device *dev, 
				       needs_clflush);



		mutex_lock(&dev->struct_mutex);

		page_cache_release(page);



next_page:

		mark_page_accessed(page);

		if (release_page)

			page_cache_release(page);



		if (ret) {

			ret = -EFAULT;

		if (ret)

			goto out;

		}



		remain -= page_length;

		user_data += page_length;
@@ -505,6 +493,8 @@ next_page: 
	}



out:

	i915_gem_object_unpin_pages(obj);



	if (hit_slowpath) {

		/* Fixup: Kill any reinstated backing storage pages */

		if (obj->madv == __I915_MADV_PURGED)

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