drivers/gpu/drm/ttm/ttm_tt.c - arm/linux-arm64-legacy - Git at Google

 /**************************************************************************
  *
  * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
  * All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the
  * "Software"), to deal in the Software without restriction, including
  * without limitation the rights to use, copy, modify, merge, publish,
  * distribute, sub license, and/or sell copies of the Software, and to
  * permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
  *
  * The above copyright notice and this permission notice (including the
  * next paragraph) shall be included in all copies or substantial portions
  * of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  *
  **************************************************************************/
 /*
  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  */

 #define pr_fmt(fmt) "[TTM] " fmt

 #include <linux/sched.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
 #include <linux/shmem_fs.h>
 #include <linux/file.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include <linux/export.h>
 #include <drm/drm_cache.h>
 #include <drm/drm_mem_util.h>
 #include <drm/ttm/ttm_module.h>
 #include <drm/ttm/ttm_bo_driver.h>
 #include <drm/ttm/ttm_placement.h>
 #include <drm/ttm/ttm_page_alloc.h>

 /**
  * Allocates storage for pointers to the pages that back the ttm.
  */
 static void ttm_tt_alloc_page_directory(struct ttm_tt *ttm)
 {
 	ttm->pages = drm_calloc_large(ttm->num_pages, sizeof(void*));
 }

 static void ttm_dma_tt_alloc_page_directory(struct ttm_dma_tt *ttm)
 {
 	ttm->ttm.pages = drm_calloc_large(ttm->ttm.num_pages, sizeof(void*));
 	ttm->dma_address = drm_calloc_large(ttm->ttm.num_pages,
 					    sizeof(*ttm->dma_address));
 }

 #ifdef CONFIG_X86
 static inline int ttm_tt_set_page_caching(struct page *p,
 					  enum ttm_caching_state c_old,
 					  enum ttm_caching_state c_new)
 {
 	int ret = 0;

 	if (PageHighMem(p))
 		return 0;

 	if (c_old != tt_cached) {
 		/* p isn't in the default caching state, set it to
 		 * writeback first to free its current memtype. */

 		ret = set_pages_wb(p, 1);
 		if (ret)
 			return ret;
 	}

 	if (c_new == tt_wc)
 		ret = set_memory_wc((unsigned long) page_address(p), 1);
 	else if (c_new == tt_uncached)
 		ret = set_pages_uc(p, 1);

 	return ret;
 }
 #else /* CONFIG_X86 */
 static inline int ttm_tt_set_page_caching(struct page *p,
 					  enum ttm_caching_state c_old,
 					  enum ttm_caching_state c_new)
 {
 	return 0;
 }
 #endif /* CONFIG_X86 */

 /*
  * Change caching policy for the linear kernel map
  * for range of pages in a ttm.
  */

 static int ttm_tt_set_caching(struct ttm_tt *ttm,
 			      enum ttm_caching_state c_state)
 {
 	int i, j;
 	struct page *cur_page;
 	int ret;

 	if (ttm->caching_state == c_state)
 		return 0;

 	if (ttm->state == tt_unpopulated) {
 		/* Change caching but don't populate */
 		ttm->caching_state = c_state;
 		return 0;
 	}

 	if (ttm->caching_state == tt_cached)
 		drm_clflush_pages(ttm->pages, ttm->num_pages);

 	for (i = 0; i < ttm->num_pages; ++i) {
 		cur_page = ttm->pages[i];
 		if (likely(cur_page != NULL)) {
 			ret = ttm_tt_set_page_caching(cur_page,
 						      ttm->caching_state,
 						      c_state);
 			if (unlikely(ret != 0))
 				goto out_err;
 		}
 	}

 	ttm->caching_state = c_state;

 	return 0;

 out_err:
 	for (j = 0; j < i; ++j) {
 		cur_page = ttm->pages[j];
 		if (likely(cur_page != NULL)) {
 			(void)ttm_tt_set_page_caching(cur_page, c_state,
 						      ttm->caching_state);
 		}
 	}

 	return ret;
 }

 int ttm_tt_set_placement_caching(struct ttm_tt *ttm, uint32_t placement)
 {
 	enum ttm_caching_state state;

 	if (placement & TTM_PL_FLAG_WC)
 		state = tt_wc;
 	else if (placement & TTM_PL_FLAG_UNCACHED)
 		state = tt_uncached;
 	else
 		state = tt_cached;

 	return ttm_tt_set_caching(ttm, state);
 }
 EXPORT_SYMBOL(ttm_tt_set_placement_caching);

 void ttm_tt_destroy(struct ttm_tt *ttm)
 {
 	if (unlikely(ttm == NULL))
 		return;

 	if (ttm->state == tt_bound) {
 		ttm_tt_unbind(ttm);
 	}

 	if (ttm->state == tt_unbound)
 		ttm_tt_unpopulate(ttm);

 	if (!(ttm->page_flags & TTM_PAGE_FLAG_PERSISTENT_SWAP) &&
 	    ttm->swap_storage)
 		fput(ttm->swap_storage);

 	ttm->swap_storage = NULL;
 	ttm->func->destroy(ttm);
 }

 int ttm_tt_init(struct ttm_tt *ttm, struct ttm_bo_device *bdev,
 		unsigned long size, uint32_t page_flags,
 		struct page *dummy_read_page)
 {
 	ttm->bdev = bdev;
 	ttm->glob = bdev->glob;
 	ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	ttm->caching_state = tt_cached;
 	ttm->page_flags = page_flags;
 	ttm->dummy_read_page = dummy_read_page;
 	ttm->state = tt_unpopulated;
 	ttm->swap_storage = NULL;

 	ttm_tt_alloc_page_directory(ttm);
 	if (!ttm->pages) {
 		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
 	}
 	return 0;
 }
 EXPORT_SYMBOL(ttm_tt_init);

 void ttm_tt_fini(struct ttm_tt *ttm)
 {
 	drm_free_large(ttm->pages);
 	ttm->pages = NULL;
 }
 EXPORT_SYMBOL(ttm_tt_fini);

 int ttm_dma_tt_init(struct ttm_dma_tt *ttm_dma, struct ttm_bo_device *bdev,
 		unsigned long size, uint32_t page_flags,
 		struct page *dummy_read_page)
 {
 	struct ttm_tt *ttm = &ttm_dma->ttm;

 	ttm->bdev = bdev;
 	ttm->glob = bdev->glob;
 	ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	ttm->caching_state = tt_cached;
 	ttm->page_flags = page_flags;
 	ttm->dummy_read_page = dummy_read_page;
 	ttm->state = tt_unpopulated;
 	ttm->swap_storage = NULL;

 	INIT_LIST_HEAD(&ttm_dma->pages_list);
 	ttm_dma_tt_alloc_page_directory(ttm_dma);
 	if (!ttm->pages || !ttm_dma->dma_address) {
 		ttm_tt_destroy(ttm);
 		pr_err("Failed allocating page table\n");
 		return -ENOMEM;
 	}
 	return 0;
 }
 EXPORT_SYMBOL(ttm_dma_tt_init);

 void ttm_dma_tt_fini(struct ttm_dma_tt *ttm_dma)
 {
 	struct ttm_tt *ttm = &ttm_dma->ttm;

 	drm_free_large(ttm->pages);
 	ttm->pages = NULL;
 	drm_free_large(ttm_dma->dma_address);
 	ttm_dma->dma_address = NULL;
 }
 EXPORT_SYMBOL(ttm_dma_tt_fini);

 void ttm_tt_unbind(struct ttm_tt *ttm)
 {
 	int ret;

 	if (ttm->state == tt_bound) {
 		ret = ttm->func->unbind(ttm);
 		BUG_ON(ret);
 		ttm->state = tt_unbound;
 	}
 }

 int ttm_tt_bind(struct ttm_tt *ttm, struct ttm_mem_reg *bo_mem)
 {
 	int ret = 0;

 	if (!ttm)
 		return -EINVAL;

 	if (ttm->state == tt_bound)
 		return 0;

 	ret = ttm->bdev->driver->ttm_tt_populate(ttm);
 	if (ret)
 		return ret;

 	ret = ttm->func->bind(ttm, bo_mem);
 	if (unlikely(ret != 0))
 		return ret;

 	ttm->state = tt_bound;

 	return 0;
 }
 EXPORT_SYMBOL(ttm_tt_bind);

 int ttm_tt_swapin(struct ttm_tt *ttm)
 {
 	struct address_space *swap_space;
 	struct file *swap_storage;
 	struct page *from_page;
 	struct page *to_page;
 	int i;
 	int ret = -ENOMEM;

 	swap_storage = ttm->swap_storage;
 	BUG_ON(swap_storage == NULL);

 	swap_space = file_inode(swap_storage)->i_mapping;

 	for (i = 0; i < ttm->num_pages; ++i) {
 		from_page = shmem_read_mapping_page(swap_space, i);
 		if (IS_ERR(from_page)) {
 			ret = PTR_ERR(from_page);
 			goto out_err;
 		}
 		to_page = ttm->pages[i];
 		if (unlikely(to_page == NULL))
 			goto out_err;

 		copy_highpage(to_page, from_page);
 		page_cache_release(from_page);
 	}

 	if (!(ttm->page_flags & TTM_PAGE_FLAG_PERSISTENT_SWAP))
 		fput(swap_storage);
 	ttm->swap_storage = NULL;
 	ttm->page_flags &= ~TTM_PAGE_FLAG_SWAPPED;

 	return 0;
 out_err:
 	return ret;
 }

 int ttm_tt_swapout(struct ttm_tt *ttm, struct file *persistent_swap_storage)
 {
 	struct address_space *swap_space;
 	struct file *swap_storage;
 	struct page *from_page;
 	struct page *to_page;
 	int i;
 	int ret = -ENOMEM;

 	BUG_ON(ttm->state != tt_unbound && ttm->state != tt_unpopulated);
 	BUG_ON(ttm->caching_state != tt_cached);

 	if (!persistent_swap_storage) {
 		swap_storage = shmem_file_setup("ttm swap",
 						ttm->num_pages << PAGE_SHIFT,
 						0);
 		if (unlikely(IS_ERR(swap_storage))) {
 			pr_err("Failed allocating swap storage\n");
 			return PTR_ERR(swap_storage);
 		}
 	} else
 		swap_storage = persistent_swap_storage;

 	swap_space = file_inode(swap_storage)->i_mapping;

 	for (i = 0; i < ttm->num_pages; ++i) {
 		from_page = ttm->pages[i];
 		if (unlikely(from_page == NULL))
 			continue;
 		to_page = shmem_read_mapping_page(swap_space, i);
 		if (unlikely(IS_ERR(to_page))) {
 			ret = PTR_ERR(to_page);
 			goto out_err;
 		}
 		copy_highpage(to_page, from_page);
 		set_page_dirty(to_page);
 		mark_page_accessed(to_page);
 		page_cache_release(to_page);
 	}

 	ttm_tt_unpopulate(ttm);
 	ttm->swap_storage = swap_storage;
 	ttm->page_flags |= TTM_PAGE_FLAG_SWAPPED;
 	if (persistent_swap_storage)
 		ttm->page_flags |= TTM_PAGE_FLAG_PERSISTENT_SWAP;

 	return 0;
 out_err:
 	if (!persistent_swap_storage)
 		fput(swap_storage);

 	return ret;
 }

 static void ttm_tt_clear_mapping(struct ttm_tt *ttm)
 {
 	pgoff_t i;
 	struct page **page = ttm->pages;

 	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
 		return;

 	for (i = 0; i < ttm->num_pages; ++i) {
 		(*page)->mapping = NULL;
 		(*page++)->index = 0;
 	}
 }

 void ttm_tt_unpopulate(struct ttm_tt *ttm)
 {
 	if (ttm->state == tt_unpopulated)
 		return;

 	ttm_tt_clear_mapping(ttm);
 	ttm->bdev->driver->ttm_tt_unpopulate(ttm);
 }
	/**************************************************************************
	*
	* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
	* All Rights Reserved.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the
	* "Software"), to deal in the Software without restriction, including
	* without limitation the rights to use, copy, modify, merge, publish,
	* distribute, sub license, and/or sell copies of the Software, and to
	* permit persons to whom the Software is furnished to do so, subject to
	* the following conditions:
	*
	* The above copyright notice and this permission notice (including the
	* next paragraph) shall be included in all copies or substantial portions
	* of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
	* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
	* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
	* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
	* USE OR OTHER DEALINGS IN THE SOFTWARE.
	*
	**************************************************************************/
	/*
	* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
	*/

	#define pr_fmt(fmt) "[TTM] " fmt

	#include <linux/sched.h>
	#include <linux/highmem.h>
	#include <linux/pagemap.h>
	#include <linux/shmem_fs.h>
	#include <linux/file.h>
	#include <linux/swap.h>
	#include <linux/slab.h>
	#include <linux/export.h>
	#include <drm/drm_cache.h>
	#include <drm/drm_mem_util.h>
	#include <drm/ttm/ttm_module.h>
	#include <drm/ttm/ttm_bo_driver.h>
	#include <drm/ttm/ttm_placement.h>
	#include <drm/ttm/ttm_page_alloc.h>

	/**
	* Allocates storage for pointers to the pages that back the ttm.
	*/
	static void ttm_tt_alloc_page_directory(struct ttm_tt *ttm)
	{
	ttm->pages = drm_calloc_large(ttm->num_pages, sizeof(void*));
	}

	static void ttm_dma_tt_alloc_page_directory(struct ttm_dma_tt *ttm)
	{
	ttm->ttm.pages = drm_calloc_large(ttm->ttm.num_pages, sizeof(void*));
	ttm->dma_address = drm_calloc_large(ttm->ttm.num_pages,
	sizeof(*ttm->dma_address));
	}

	#ifdef CONFIG_X86
	static inline int ttm_tt_set_page_caching(struct page *p,
	enum ttm_caching_state c_old,
	enum ttm_caching_state c_new)
	{
	int ret = 0;

	if (PageHighMem(p))
	return 0;

	if (c_old != tt_cached) {
	/* p isn't in the default caching state, set it to
	* writeback first to free its current memtype. */

	ret = set_pages_wb(p, 1);
	if (ret)
	return ret;
	}

	if (c_new == tt_wc)
	ret = set_memory_wc((unsigned long) page_address(p), 1);
	else if (c_new == tt_uncached)
	ret = set_pages_uc(p, 1);

	return ret;
	}
	#else /* CONFIG_X86 */
	static inline int ttm_tt_set_page_caching(struct page *p,
	enum ttm_caching_state c_old,
	enum ttm_caching_state c_new)
	{
	return 0;
	}
	#endif /* CONFIG_X86 */

	/*
	* Change caching policy for the linear kernel map
	* for range of pages in a ttm.
	*/

	static int ttm_tt_set_caching(struct ttm_tt *ttm,
	enum ttm_caching_state c_state)
	{
	int i, j;
	struct page *cur_page;
	int ret;

	if (ttm->caching_state == c_state)
	return 0;

	if (ttm->state == tt_unpopulated) {
	/* Change caching but don't populate */
	ttm->caching_state = c_state;
	return 0;
	}

	if (ttm->caching_state == tt_cached)
	drm_clflush_pages(ttm->pages, ttm->num_pages);

	for (i = 0; i < ttm->num_pages; ++i) {
	cur_page = ttm->pages[i];
	if (likely(cur_page != NULL)) {
	ret = ttm_tt_set_page_caching(cur_page,
	ttm->caching_state,
	c_state);
	if (unlikely(ret != 0))
	goto out_err;
	}
	}

	ttm->caching_state = c_state;

	return 0;

	out_err:
	for (j = 0; j < i; ++j) {
	cur_page = ttm->pages[j];
	if (likely(cur_page != NULL)) {
	(void)ttm_tt_set_page_caching(cur_page, c_state,
	ttm->caching_state);
	}
	}

	return ret;
	}

	int ttm_tt_set_placement_caching(struct ttm_tt *ttm, uint32_t placement)
	{
	enum ttm_caching_state state;

	if (placement & TTM_PL_FLAG_WC)
	state = tt_wc;
	else if (placement & TTM_PL_FLAG_UNCACHED)
	state = tt_uncached;
	else
	state = tt_cached;

	return ttm_tt_set_caching(ttm, state);
	}
	EXPORT_SYMBOL(ttm_tt_set_placement_caching);

	void ttm_tt_destroy(struct ttm_tt *ttm)
	{
	if (unlikely(ttm == NULL))
	return;

	if (ttm->state == tt_bound) {
	ttm_tt_unbind(ttm);
	}

	if (ttm->state == tt_unbound)
	ttm_tt_unpopulate(ttm);

	if (!(ttm->page_flags & TTM_PAGE_FLAG_PERSISTENT_SWAP) &&
	ttm->swap_storage)
	fput(ttm->swap_storage);

	ttm->swap_storage = NULL;
	ttm->func->destroy(ttm);
	}

	int ttm_tt_init(struct ttm_tt ttm, struct ttm_bo_device bdev,
	unsigned long size, uint32_t page_flags,
	struct page *dummy_read_page)
	{
	ttm->bdev = bdev;
	ttm->glob = bdev->glob;
	ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	ttm->caching_state = tt_cached;
	ttm->page_flags = page_flags;
	ttm->dummy_read_page = dummy_read_page;
	ttm->state = tt_unpopulated;
	ttm->swap_storage = NULL;

	ttm_tt_alloc_page_directory(ttm);
	if (!ttm->pages) {
	ttm_tt_destroy(ttm);
	pr_err("Failed allocating page table\n");
	return -ENOMEM;
	}
	return 0;
	}
	EXPORT_SYMBOL(ttm_tt_init);

	void ttm_tt_fini(struct ttm_tt *ttm)
	{
	drm_free_large(ttm->pages);
	ttm->pages = NULL;
	}
	EXPORT_SYMBOL(ttm_tt_fini);

	int ttm_dma_tt_init(struct ttm_dma_tt ttm_dma, struct ttm_bo_device bdev,
	unsigned long size, uint32_t page_flags,
	struct page *dummy_read_page)
	{
	struct ttm_tt *ttm = &ttm_dma->ttm;

	ttm->bdev = bdev;
	ttm->glob = bdev->glob;
	ttm->num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
	ttm->caching_state = tt_cached;
	ttm->page_flags = page_flags;
	ttm->dummy_read_page = dummy_read_page;
	ttm->state = tt_unpopulated;
	ttm->swap_storage = NULL;

	INIT_LIST_HEAD(&ttm_dma->pages_list);
	ttm_dma_tt_alloc_page_directory(ttm_dma);
	if (!ttm->pages \|\| !ttm_dma->dma_address) {
	ttm_tt_destroy(ttm);
	pr_err("Failed allocating page table\n");
	return -ENOMEM;
	}
	return 0;
	}
	EXPORT_SYMBOL(ttm_dma_tt_init);

	void ttm_dma_tt_fini(struct ttm_dma_tt *ttm_dma)
	{
	struct ttm_tt *ttm = &ttm_dma->ttm;

	drm_free_large(ttm->pages);
	ttm->pages = NULL;
	drm_free_large(ttm_dma->dma_address);
	ttm_dma->dma_address = NULL;
	}
	EXPORT_SYMBOL(ttm_dma_tt_fini);

	void ttm_tt_unbind(struct ttm_tt *ttm)
	{
	int ret;

	if (ttm->state == tt_bound) {
	ret = ttm->func->unbind(ttm);
	BUG_ON(ret);
	ttm->state = tt_unbound;
	}
	}

	int ttm_tt_bind(struct ttm_tt ttm, struct ttm_mem_reg bo_mem)
	{
	int ret = 0;

	if (!ttm)
	return -EINVAL;

	if (ttm->state == tt_bound)
	return 0;

	ret = ttm->bdev->driver->ttm_tt_populate(ttm);
	if (ret)
	return ret;

	ret = ttm->func->bind(ttm, bo_mem);
	if (unlikely(ret != 0))
	return ret;

	ttm->state = tt_bound;

	return 0;
	}
	EXPORT_SYMBOL(ttm_tt_bind);

	int ttm_tt_swapin(struct ttm_tt *ttm)
	{
	struct address_space *swap_space;
	struct file *swap_storage;
	struct page *from_page;
	struct page *to_page;
	int i;
	int ret = -ENOMEM;

	swap_storage = ttm->swap_storage;
	BUG_ON(swap_storage == NULL);

	swap_space = file_inode(swap_storage)->i_mapping;

	for (i = 0; i < ttm->num_pages; ++i) {
	from_page = shmem_read_mapping_page(swap_space, i);
	if (IS_ERR(from_page)) {
	ret = PTR_ERR(from_page);
	goto out_err;
	}
	to_page = ttm->pages[i];
	if (unlikely(to_page == NULL))
	goto out_err;

	copy_highpage(to_page, from_page);
	page_cache_release(from_page);
	}

	if (!(ttm->page_flags & TTM_PAGE_FLAG_PERSISTENT_SWAP))
	fput(swap_storage);
	ttm->swap_storage = NULL;
	ttm->page_flags &= ~TTM_PAGE_FLAG_SWAPPED;

	return 0;
	out_err:
	return ret;
	}

	int ttm_tt_swapout(struct ttm_tt ttm, struct file persistent_swap_storage)
	{
	struct address_space *swap_space;
	struct file *swap_storage;
	struct page *from_page;
	struct page *to_page;
	int i;
	int ret = -ENOMEM;

	BUG_ON(ttm->state != tt_unbound && ttm->state != tt_unpopulated);
	BUG_ON(ttm->caching_state != tt_cached);

	if (!persistent_swap_storage) {
	swap_storage = shmem_file_setup("ttm swap",
	ttm->num_pages << PAGE_SHIFT,
	0);
	if (unlikely(IS_ERR(swap_storage))) {
	pr_err("Failed allocating swap storage\n");
	return PTR_ERR(swap_storage);
	}
	} else
	swap_storage = persistent_swap_storage;

	swap_space = file_inode(swap_storage)->i_mapping;

	for (i = 0; i < ttm->num_pages; ++i) {
	from_page = ttm->pages[i];
	if (unlikely(from_page == NULL))
	continue;
	to_page = shmem_read_mapping_page(swap_space, i);
	if (unlikely(IS_ERR(to_page))) {
	ret = PTR_ERR(to_page);
	goto out_err;
	}
	copy_highpage(to_page, from_page);
	set_page_dirty(to_page);
	mark_page_accessed(to_page);
	page_cache_release(to_page);
	}

	ttm_tt_unpopulate(ttm);
	ttm->swap_storage = swap_storage;
	ttm->page_flags \|= TTM_PAGE_FLAG_SWAPPED;
	if (persistent_swap_storage)
	ttm->page_flags \|= TTM_PAGE_FLAG_PERSISTENT_SWAP;

	return 0;
	out_err:
	if (!persistent_swap_storage)
	fput(swap_storage);

	return ret;
	}

	static void ttm_tt_clear_mapping(struct ttm_tt *ttm)
	{
	pgoff_t i;
	struct page **page = ttm->pages;

	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
	return;

	for (i = 0; i < ttm->num_pages; ++i) {
	(*page)->mapping = NULL;
	(*page++)->index = 0;
	}
	}

	void ttm_tt_unpopulate(struct ttm_tt *ttm)
	{
	if (ttm->state == tt_unpopulated)
	return;

	ttm_tt_clear_mapping(ttm);
	ttm->bdev->driver->ttm_tt_unpopulate(ttm);
	}