1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2014-2016 Intel Corporation
5  */
6 
7 #include <linux/pagevec.h>
8 #include <linux/shmem_fs.h>
9 #include <linux/swap.h>
10 
11 #include <drm/drm_cache.h>
12 
13 #include "gem/i915_gem_region.h"
14 #include "i915_drv.h"
15 #include "i915_gem_object.h"
16 #include "i915_gem_tiling.h"
17 #include "i915_gemfs.h"
18 #include "i915_scatterlist.h"
19 #include "i915_trace.h"
20 
21 /*
22  * Move folios to appropriate lru and release the batch, decrementing the
23  * ref count of those folios.
24  */
25 static void check_release_folio_batch(struct folio_batch *fbatch)
26 {
27 	check_move_unevictable_folios(fbatch);
28 	__folio_batch_release(fbatch);
29 	cond_resched();
30 }
31 
32 void shmem_sg_free_table(struct sg_table *st, struct address_space *mapping,
33 			 bool dirty, bool backup)
34 {
35 	struct sgt_iter sgt_iter;
36 	struct folio_batch fbatch;
37 	struct folio *last = NULL;
38 	struct page *page;
39 
40 	mapping_clear_unevictable(mapping);
41 
42 	folio_batch_init(&fbatch);
43 	for_each_sgt_page(page, sgt_iter, st) {
44 		struct folio *folio = page_folio(page);
45 
46 		if (folio == last)
47 			continue;
48 		last = folio;
49 		if (dirty)
50 			folio_mark_dirty(folio);
51 		if (backup)
52 			folio_mark_accessed(folio);
53 
54 		if (!folio_batch_add(&fbatch, folio))
55 			check_release_folio_batch(&fbatch);
56 	}
57 	if (fbatch.nr)
58 		check_release_folio_batch(&fbatch);
59 
60 	sg_free_table(st);
61 }
62 
63 int shmem_sg_alloc_table(struct drm_i915_private *i915, struct sg_table *st,
64 			 size_t size, struct intel_memory_region *mr,
65 			 struct address_space *mapping,
66 			 unsigned int max_segment)
67 {
68 	unsigned int page_count; /* restricted by sg_alloc_table */
69 	unsigned long i;
70 	struct scatterlist *sg;
71 	unsigned long next_pfn = 0;	/* suppress gcc warning */
72 	gfp_t noreclaim;
73 	int ret;
74 
75 	if (overflows_type(size / PAGE_SIZE, page_count))
76 		return -E2BIG;
77 
78 	page_count = size / PAGE_SIZE;
79 	/*
80 	 * If there's no chance of allocating enough pages for the whole
81 	 * object, bail early.
82 	 */
83 	if (size > resource_size(&mr->region))
84 		return -ENOMEM;
85 
86 	if (sg_alloc_table(st, page_count, GFP_KERNEL | __GFP_NOWARN))
87 		return -ENOMEM;
88 
89 	/*
90 	 * Get the list of pages out of our struct file.  They'll be pinned
91 	 * at this point until we release them.
92 	 *
93 	 * Fail silently without starting the shrinker
94 	 */
95 	mapping_set_unevictable(mapping);
96 	noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
97 	noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
98 
99 	sg = st->sgl;
100 	st->nents = 0;
101 	for (i = 0; i < page_count; i++) {
102 		struct folio *folio;
103 		unsigned long nr_pages;
104 		const unsigned int shrink[] = {
105 			I915_SHRINK_BOUND | I915_SHRINK_UNBOUND,
106 			0,
107 		}, *s = shrink;
108 		gfp_t gfp = noreclaim;
109 
110 		do {
111 			cond_resched();
112 			folio = shmem_read_folio_gfp(mapping, i, gfp);
113 			if (!IS_ERR(folio))
114 				break;
115 
116 			if (!*s) {
117 				ret = PTR_ERR(folio);
118 				goto err_sg;
119 			}
120 
121 			i915_gem_shrink(NULL, i915, 2 * page_count, NULL, *s++);
122 
123 			/*
124 			 * We've tried hard to allocate the memory by reaping
125 			 * our own buffer, now let the real VM do its job and
126 			 * go down in flames if truly OOM.
127 			 *
128 			 * However, since graphics tend to be disposable,
129 			 * defer the oom here by reporting the ENOMEM back
130 			 * to userspace.
131 			 */
132 			if (!*s) {
133 				/* reclaim and warn, but no oom */
134 				gfp = mapping_gfp_mask(mapping);
135 
136 				/*
137 				 * Our bo are always dirty and so we require
138 				 * kswapd to reclaim our pages (direct reclaim
139 				 * does not effectively begin pageout of our
140 				 * buffers on its own). However, direct reclaim
141 				 * only waits for kswapd when under allocation
142 				 * congestion. So as a result __GFP_RECLAIM is
143 				 * unreliable and fails to actually reclaim our
144 				 * dirty pages -- unless you try over and over
145 				 * again with !__GFP_NORETRY. However, we still
146 				 * want to fail this allocation rather than
147 				 * trigger the out-of-memory killer and for
148 				 * this we want __GFP_RETRY_MAYFAIL.
149 				 */
150 				gfp |= __GFP_RETRY_MAYFAIL | __GFP_NOWARN;
151 			}
152 		} while (1);
153 
154 		nr_pages = min_t(unsigned long,
155 				folio_nr_pages(folio), page_count - i);
156 		if (!i ||
157 		    sg->length >= max_segment ||
158 		    folio_pfn(folio) != next_pfn) {
159 			if (i)
160 				sg = sg_next(sg);
161 
162 			st->nents++;
163 			sg_set_folio(sg, folio, nr_pages * PAGE_SIZE, 0);
164 		} else {
165 			/* XXX: could overflow? */
166 			sg->length += nr_pages * PAGE_SIZE;
167 		}
168 		next_pfn = folio_pfn(folio) + nr_pages;
169 		i += nr_pages - 1;
170 
171 		/* Check that the i965g/gm workaround works. */
172 		GEM_BUG_ON(gfp & __GFP_DMA32 && next_pfn >= 0x00100000UL);
173 	}
174 	if (sg) /* loop terminated early; short sg table */
175 		sg_mark_end(sg);
176 
177 	/* Trim unused sg entries to avoid wasting memory. */
178 	i915_sg_trim(st);
179 
180 	return 0;
181 err_sg:
182 	sg_mark_end(sg);
183 	if (sg != st->sgl) {
184 		shmem_sg_free_table(st, mapping, false, false);
185 	} else {
186 		mapping_clear_unevictable(mapping);
187 		sg_free_table(st);
188 	}
189 
190 	/*
191 	 * shmemfs first checks if there is enough memory to allocate the page
192 	 * and reports ENOSPC should there be insufficient, along with the usual
193 	 * ENOMEM for a genuine allocation failure.
194 	 *
195 	 * We use ENOSPC in our driver to mean that we have run out of aperture
196 	 * space and so want to translate the error from shmemfs back to our
197 	 * usual understanding of ENOMEM.
198 	 */
199 	if (ret == -ENOSPC)
200 		ret = -ENOMEM;
201 
202 	return ret;
203 }
204 
205 static int shmem_get_pages(struct drm_i915_gem_object *obj)
206 {
207 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
208 	struct intel_memory_region *mem = obj->mm.region;
209 	struct address_space *mapping = obj->base.filp->f_mapping;
210 	unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
211 	struct sg_table *st;
212 	struct sgt_iter sgt_iter;
213 	struct page *page;
214 	int ret;
215 
216 	/*
217 	 * Assert that the object is not currently in any GPU domain. As it
218 	 * wasn't in the GTT, there shouldn't be any way it could have been in
219 	 * a GPU cache
220 	 */
221 	GEM_BUG_ON(obj->read_domains & I915_GEM_GPU_DOMAINS);
222 	GEM_BUG_ON(obj->write_domain & I915_GEM_GPU_DOMAINS);
223 
224 rebuild_st:
225 	st = kmalloc(sizeof(*st), GFP_KERNEL | __GFP_NOWARN);
226 	if (!st)
227 		return -ENOMEM;
228 
229 	ret = shmem_sg_alloc_table(i915, st, obj->base.size, mem, mapping,
230 				   max_segment);
231 	if (ret)
232 		goto err_st;
233 
234 	ret = i915_gem_gtt_prepare_pages(obj, st);
235 	if (ret) {
236 		/*
237 		 * DMA remapping failed? One possible cause is that
238 		 * it could not reserve enough large entries, asking
239 		 * for PAGE_SIZE chunks instead may be helpful.
240 		 */
241 		if (max_segment > PAGE_SIZE) {
242 			for_each_sgt_page(page, sgt_iter, st)
243 				put_page(page);
244 			sg_free_table(st);
245 			kfree(st);
246 
247 			max_segment = PAGE_SIZE;
248 			goto rebuild_st;
249 		} else {
250 			dev_warn(i915->drm.dev,
251 				 "Failed to DMA remap %zu pages\n",
252 				 obj->base.size >> PAGE_SHIFT);
253 			goto err_pages;
254 		}
255 	}
256 
257 	if (i915_gem_object_needs_bit17_swizzle(obj))
258 		i915_gem_object_do_bit_17_swizzle(obj, st);
259 
260 	if (i915_gem_object_can_bypass_llc(obj))
261 		obj->cache_dirty = true;
262 
263 	__i915_gem_object_set_pages(obj, st);
264 
265 	return 0;
266 
267 err_pages:
268 	shmem_sg_free_table(st, mapping, false, false);
269 	/*
270 	 * shmemfs first checks if there is enough memory to allocate the page
271 	 * and reports ENOSPC should there be insufficient, along with the usual
272 	 * ENOMEM for a genuine allocation failure.
273 	 *
274 	 * We use ENOSPC in our driver to mean that we have run out of aperture
275 	 * space and so want to translate the error from shmemfs back to our
276 	 * usual understanding of ENOMEM.
277 	 */
278 err_st:
279 	if (ret == -ENOSPC)
280 		ret = -ENOMEM;
281 
282 	kfree(st);
283 
284 	return ret;
285 }
286 
287 static int
288 shmem_truncate(struct drm_i915_gem_object *obj)
289 {
290 	/*
291 	 * Our goal here is to return as much of the memory as
292 	 * is possible back to the system as we are called from OOM.
293 	 * To do this we must instruct the shmfs to drop all of its
294 	 * backing pages, *now*.
295 	 */
296 	shmem_truncate_range(file_inode(obj->base.filp), 0, (loff_t)-1);
297 	obj->mm.madv = __I915_MADV_PURGED;
298 	obj->mm.pages = ERR_PTR(-EFAULT);
299 
300 	return 0;
301 }
302 
303 void __shmem_writeback(size_t size, struct address_space *mapping)
304 {
305 	struct writeback_control wbc = {
306 		.sync_mode = WB_SYNC_NONE,
307 		.nr_to_write = SWAP_CLUSTER_MAX,
308 		.range_start = 0,
309 		.range_end = LLONG_MAX,
310 		.for_reclaim = 1,
311 	};
312 	unsigned long i;
313 
314 	/*
315 	 * Leave mmapings intact (GTT will have been revoked on unbinding,
316 	 * leaving only CPU mmapings around) and add those pages to the LRU
317 	 * instead of invoking writeback so they are aged and paged out
318 	 * as normal.
319 	 */
320 
321 	/* Begin writeback on each dirty page */
322 	for (i = 0; i < size >> PAGE_SHIFT; i++) {
323 		struct page *page;
324 
325 		page = find_lock_page(mapping, i);
326 		if (!page)
327 			continue;
328 
329 		if (!page_mapped(page) && clear_page_dirty_for_io(page)) {
330 			int ret;
331 
332 			SetPageReclaim(page);
333 			ret = mapping->a_ops->writepage(page, &wbc);
334 			if (!PageWriteback(page))
335 				ClearPageReclaim(page);
336 			if (!ret)
337 				goto put;
338 		}
339 		unlock_page(page);
340 put:
341 		put_page(page);
342 	}
343 }
344 
345 static void
346 shmem_writeback(struct drm_i915_gem_object *obj)
347 {
348 	__shmem_writeback(obj->base.size, obj->base.filp->f_mapping);
349 }
350 
351 static int shmem_shrink(struct drm_i915_gem_object *obj, unsigned int flags)
352 {
353 	switch (obj->mm.madv) {
354 	case I915_MADV_DONTNEED:
355 		return i915_gem_object_truncate(obj);
356 	case __I915_MADV_PURGED:
357 		return 0;
358 	}
359 
360 	if (flags & I915_GEM_OBJECT_SHRINK_WRITEBACK)
361 		shmem_writeback(obj);
362 
363 	return 0;
364 }
365 
366 void
367 __i915_gem_object_release_shmem(struct drm_i915_gem_object *obj,
368 				struct sg_table *pages,
369 				bool needs_clflush)
370 {
371 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
372 
373 	GEM_BUG_ON(obj->mm.madv == __I915_MADV_PURGED);
374 
375 	if (obj->mm.madv == I915_MADV_DONTNEED)
376 		obj->mm.dirty = false;
377 
378 	if (needs_clflush &&
379 	    (obj->read_domains & I915_GEM_DOMAIN_CPU) == 0 &&
380 	    !(obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ))
381 		drm_clflush_sg(pages);
382 
383 	__start_cpu_write(obj);
384 	/*
385 	 * On non-LLC igfx platforms, force the flush-on-acquire if this is ever
386 	 * swapped-in. Our async flush path is not trust worthy enough yet(and
387 	 * happens in the wrong order), and with some tricks it's conceivable
388 	 * for userspace to change the cache-level to I915_CACHE_NONE after the
389 	 * pages are swapped-in, and since execbuf binds the object before doing
390 	 * the async flush, we have a race window.
391 	 */
392 	if (!HAS_LLC(i915) && !IS_DGFX(i915))
393 		obj->cache_dirty = true;
394 }
395 
396 void i915_gem_object_put_pages_shmem(struct drm_i915_gem_object *obj, struct sg_table *pages)
397 {
398 	__i915_gem_object_release_shmem(obj, pages, true);
399 
400 	i915_gem_gtt_finish_pages(obj, pages);
401 
402 	if (i915_gem_object_needs_bit17_swizzle(obj))
403 		i915_gem_object_save_bit_17_swizzle(obj, pages);
404 
405 	shmem_sg_free_table(pages, file_inode(obj->base.filp)->i_mapping,
406 			    obj->mm.dirty, obj->mm.madv == I915_MADV_WILLNEED);
407 	kfree(pages);
408 	obj->mm.dirty = false;
409 }
410 
411 static void
412 shmem_put_pages(struct drm_i915_gem_object *obj, struct sg_table *pages)
413 {
414 	if (likely(i915_gem_object_has_struct_page(obj)))
415 		i915_gem_object_put_pages_shmem(obj, pages);
416 	else
417 		i915_gem_object_put_pages_phys(obj, pages);
418 }
419 
420 static int
421 shmem_pwrite(struct drm_i915_gem_object *obj,
422 	     const struct drm_i915_gem_pwrite *arg)
423 {
424 	struct address_space *mapping = obj->base.filp->f_mapping;
425 	const struct address_space_operations *aops = mapping->a_ops;
426 	char __user *user_data = u64_to_user_ptr(arg->data_ptr);
427 	u64 remain, offset;
428 	unsigned int pg;
429 
430 	/* Caller already validated user args */
431 	GEM_BUG_ON(!access_ok(user_data, arg->size));
432 
433 	if (!i915_gem_object_has_struct_page(obj))
434 		return i915_gem_object_pwrite_phys(obj, arg);
435 
436 	/*
437 	 * Before we instantiate/pin the backing store for our use, we
438 	 * can prepopulate the shmemfs filp efficiently using a write into
439 	 * the pagecache. We avoid the penalty of instantiating all the
440 	 * pages, important if the user is just writing to a few and never
441 	 * uses the object on the GPU, and using a direct write into shmemfs
442 	 * allows it to avoid the cost of retrieving a page (either swapin
443 	 * or clearing-before-use) before it is overwritten.
444 	 */
445 	if (i915_gem_object_has_pages(obj))
446 		return -ENODEV;
447 
448 	if (obj->mm.madv != I915_MADV_WILLNEED)
449 		return -EFAULT;
450 
451 	/*
452 	 * Before the pages are instantiated the object is treated as being
453 	 * in the CPU domain. The pages will be clflushed as required before
454 	 * use, and we can freely write into the pages directly. If userspace
455 	 * races pwrite with any other operation; corruption will ensue -
456 	 * that is userspace's prerogative!
457 	 */
458 
459 	remain = arg->size;
460 	offset = arg->offset;
461 	pg = offset_in_page(offset);
462 
463 	do {
464 		unsigned int len, unwritten;
465 		struct page *page;
466 		void *data, *vaddr;
467 		int err;
468 		char __maybe_unused c;
469 
470 		len = PAGE_SIZE - pg;
471 		if (len > remain)
472 			len = remain;
473 
474 		/* Prefault the user page to reduce potential recursion */
475 		err = __get_user(c, user_data);
476 		if (err)
477 			return err;
478 
479 		err = __get_user(c, user_data + len - 1);
480 		if (err)
481 			return err;
482 
483 		err = aops->write_begin(obj->base.filp, mapping, offset, len,
484 					&page, &data);
485 		if (err < 0)
486 			return err;
487 
488 		vaddr = kmap_atomic(page);
489 		unwritten = __copy_from_user_inatomic(vaddr + pg,
490 						      user_data,
491 						      len);
492 		kunmap_atomic(vaddr);
493 
494 		err = aops->write_end(obj->base.filp, mapping, offset, len,
495 				      len - unwritten, page, data);
496 		if (err < 0)
497 			return err;
498 
499 		/* We don't handle -EFAULT, leave it to the caller to check */
500 		if (unwritten)
501 			return -ENODEV;
502 
503 		remain -= len;
504 		user_data += len;
505 		offset += len;
506 		pg = 0;
507 	} while (remain);
508 
509 	return 0;
510 }
511 
512 static int
513 shmem_pread(struct drm_i915_gem_object *obj,
514 	    const struct drm_i915_gem_pread *arg)
515 {
516 	if (!i915_gem_object_has_struct_page(obj))
517 		return i915_gem_object_pread_phys(obj, arg);
518 
519 	return -ENODEV;
520 }
521 
522 static void shmem_release(struct drm_i915_gem_object *obj)
523 {
524 	if (i915_gem_object_has_struct_page(obj))
525 		i915_gem_object_release_memory_region(obj);
526 
527 	fput(obj->base.filp);
528 }
529 
530 const struct drm_i915_gem_object_ops i915_gem_shmem_ops = {
531 	.name = "i915_gem_object_shmem",
532 	.flags = I915_GEM_OBJECT_IS_SHRINKABLE,
533 
534 	.get_pages = shmem_get_pages,
535 	.put_pages = shmem_put_pages,
536 	.truncate = shmem_truncate,
537 	.shrink = shmem_shrink,
538 
539 	.pwrite = shmem_pwrite,
540 	.pread = shmem_pread,
541 
542 	.release = shmem_release,
543 };
544 
545 static int __create_shmem(struct drm_i915_private *i915,
546 			  struct drm_gem_object *obj,
547 			  resource_size_t size)
548 {
549 	unsigned long flags = VM_NORESERVE;
550 	struct file *filp;
551 
552 	drm_gem_private_object_init(&i915->drm, obj, size);
553 
554 	/* XXX: The __shmem_file_setup() function returns -EINVAL if size is
555 	 * greater than MAX_LFS_FILESIZE.
556 	 * To handle the same error as other code that returns -E2BIG when
557 	 * the size is too large, we add a code that returns -E2BIG when the
558 	 * size is larger than the size that can be handled.
559 	 * If BITS_PER_LONG is 32, size > MAX_LFS_FILESIZE is always false,
560 	 * so we only needs to check when BITS_PER_LONG is 64.
561 	 * If BITS_PER_LONG is 32, E2BIG checks are processed when
562 	 * i915_gem_object_size_2big() is called before init_object() callback
563 	 * is called.
564 	 */
565 	if (BITS_PER_LONG == 64 && size > MAX_LFS_FILESIZE)
566 		return -E2BIG;
567 
568 	if (i915->mm.gemfs)
569 		filp = shmem_file_setup_with_mnt(i915->mm.gemfs, "i915", size,
570 						 flags);
571 	else
572 		filp = shmem_file_setup("i915", size, flags);
573 	if (IS_ERR(filp))
574 		return PTR_ERR(filp);
575 
576 	obj->filp = filp;
577 	return 0;
578 }
579 
580 static int shmem_object_init(struct intel_memory_region *mem,
581 			     struct drm_i915_gem_object *obj,
582 			     resource_size_t offset,
583 			     resource_size_t size,
584 			     resource_size_t page_size,
585 			     unsigned int flags)
586 {
587 	static struct lock_class_key lock_class;
588 	struct drm_i915_private *i915 = mem->i915;
589 	struct address_space *mapping;
590 	unsigned int cache_level;
591 	gfp_t mask;
592 	int ret;
593 
594 	ret = __create_shmem(i915, &obj->base, size);
595 	if (ret)
596 		return ret;
597 
598 	mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
599 	if (IS_I965GM(i915) || IS_I965G(i915)) {
600 		/* 965gm cannot relocate objects above 4GiB. */
601 		mask &= ~__GFP_HIGHMEM;
602 		mask |= __GFP_DMA32;
603 	}
604 
605 	mapping = obj->base.filp->f_mapping;
606 	mapping_set_gfp_mask(mapping, mask);
607 	GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));
608 
609 	i915_gem_object_init(obj, &i915_gem_shmem_ops, &lock_class, flags);
610 	obj->mem_flags |= I915_BO_FLAG_STRUCT_PAGE;
611 	obj->write_domain = I915_GEM_DOMAIN_CPU;
612 	obj->read_domains = I915_GEM_DOMAIN_CPU;
613 
614 	/*
615 	 * MTL doesn't snoop CPU cache by default for GPU access (namely
616 	 * 1-way coherency). However some UMD's are currently depending on
617 	 * that. Make 1-way coherent the default setting for MTL. A follow
618 	 * up patch will extend the GEM_CREATE uAPI to allow UMD's specify
619 	 * caching mode at BO creation time
620 	 */
621 	if (HAS_LLC(i915) || (GRAPHICS_VER_FULL(i915) >= IP_VER(12, 70)))
622 		/* On some devices, we can have the GPU use the LLC (the CPU
623 		 * cache) for about a 10% performance improvement
624 		 * compared to uncached.  Graphics requests other than
625 		 * display scanout are coherent with the CPU in
626 		 * accessing this cache.  This means in this mode we
627 		 * don't need to clflush on the CPU side, and on the
628 		 * GPU side we only need to flush internal caches to
629 		 * get data visible to the CPU.
630 		 *
631 		 * However, we maintain the display planes as UC, and so
632 		 * need to rebind when first used as such.
633 		 */
634 		cache_level = I915_CACHE_LLC;
635 	else
636 		cache_level = I915_CACHE_NONE;
637 
638 	i915_gem_object_set_cache_coherency(obj, cache_level);
639 
640 	i915_gem_object_init_memory_region(obj, mem);
641 
642 	return 0;
643 }
644 
645 struct drm_i915_gem_object *
646 i915_gem_object_create_shmem(struct drm_i915_private *i915,
647 			     resource_size_t size)
648 {
649 	return i915_gem_object_create_region(i915->mm.regions[INTEL_REGION_SMEM],
650 					     size, 0, 0);
651 }
652 
653 /* Allocate a new GEM object and fill it with the supplied data */
654 struct drm_i915_gem_object *
655 i915_gem_object_create_shmem_from_data(struct drm_i915_private *dev_priv,
656 				       const void *data, resource_size_t size)
657 {
658 	struct drm_i915_gem_object *obj;
659 	struct file *file;
660 	const struct address_space_operations *aops;
661 	resource_size_t offset;
662 	int err;
663 
664 	GEM_WARN_ON(IS_DGFX(dev_priv));
665 	obj = i915_gem_object_create_shmem(dev_priv, round_up(size, PAGE_SIZE));
666 	if (IS_ERR(obj))
667 		return obj;
668 
669 	GEM_BUG_ON(obj->write_domain != I915_GEM_DOMAIN_CPU);
670 
671 	file = obj->base.filp;
672 	aops = file->f_mapping->a_ops;
673 	offset = 0;
674 	do {
675 		unsigned int len = min_t(typeof(size), size, PAGE_SIZE);
676 		struct page *page;
677 		void *pgdata, *vaddr;
678 
679 		err = aops->write_begin(file, file->f_mapping, offset, len,
680 					&page, &pgdata);
681 		if (err < 0)
682 			goto fail;
683 
684 		vaddr = kmap(page);
685 		memcpy(vaddr, data, len);
686 		kunmap(page);
687 
688 		err = aops->write_end(file, file->f_mapping, offset, len, len,
689 				      page, pgdata);
690 		if (err < 0)
691 			goto fail;
692 
693 		size -= len;
694 		data += len;
695 		offset += len;
696 	} while (size);
697 
698 	return obj;
699 
700 fail:
701 	i915_gem_object_put(obj);
702 	return ERR_PTR(err);
703 }
704 
705 static int init_shmem(struct intel_memory_region *mem)
706 {
707 	i915_gemfs_init(mem->i915);
708 	intel_memory_region_set_name(mem, "system");
709 
710 	return 0; /* We have fallback to the kernel mnt if gemfs init failed. */
711 }
712 
713 static int release_shmem(struct intel_memory_region *mem)
714 {
715 	i915_gemfs_fini(mem->i915);
716 	return 0;
717 }
718 
719 static const struct intel_memory_region_ops shmem_region_ops = {
720 	.init = init_shmem,
721 	.release = release_shmem,
722 	.init_object = shmem_object_init,
723 };
724 
725 struct intel_memory_region *i915_gem_shmem_setup(struct drm_i915_private *i915,
726 						 u16 type, u16 instance)
727 {
728 	return intel_memory_region_create(i915, 0,
729 					  totalram_pages() << PAGE_SHIFT,
730 					  PAGE_SIZE, 0, 0,
731 					  type, instance,
732 					  &shmem_region_ops);
733 }
734 
735 bool i915_gem_object_is_shmem(const struct drm_i915_gem_object *obj)
736 {
737 	return obj->ops == &i915_gem_shmem_ops;
738 }
739