xref: /linux/drivers/block/zram/zram_drv.c (revision e0bf6c5ca2d3281f231c5f0c9bf145e9513644de)
1 /*
2  * Compressed RAM block device
3  *
4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
5  *               2012, 2013 Minchan Kim
6  *
7  * This code is released using a dual license strategy: BSD/GPL
8  * You can choose the licence that better fits your requirements.
9  *
10  * Released under the terms of 3-clause BSD License
11  * Released under the terms of GNU General Public License Version 2.0
12  *
13  */
14 
15 #define KMSG_COMPONENT "zram"
16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
17 
18 #ifdef CONFIG_ZRAM_DEBUG
19 #define DEBUG
20 #endif
21 
22 #include <linux/module.h>
23 #include <linux/kernel.h>
24 #include <linux/bio.h>
25 #include <linux/bitops.h>
26 #include <linux/blkdev.h>
27 #include <linux/buffer_head.h>
28 #include <linux/device.h>
29 #include <linux/genhd.h>
30 #include <linux/highmem.h>
31 #include <linux/slab.h>
32 #include <linux/string.h>
33 #include <linux/vmalloc.h>
34 #include <linux/err.h>
35 
36 #include "zram_drv.h"
37 
38 /* Globals */
39 static int zram_major;
40 static struct zram *zram_devices;
41 static const char *default_compressor = "lzo";
42 
43 /* Module params (documentation at end) */
44 static unsigned int num_devices = 1;
45 
46 #define ZRAM_ATTR_RO(name)						\
47 static ssize_t name##_show(struct device *d,		\
48 				struct device_attribute *attr, char *b)	\
49 {									\
50 	struct zram *zram = dev_to_zram(d);				\
51 	return scnprintf(b, PAGE_SIZE, "%llu\n",			\
52 		(u64)atomic64_read(&zram->stats.name));			\
53 }									\
54 static DEVICE_ATTR_RO(name);
55 
56 static inline bool init_done(struct zram *zram)
57 {
58 	return zram->disksize;
59 }
60 
61 static inline struct zram *dev_to_zram(struct device *dev)
62 {
63 	return (struct zram *)dev_to_disk(dev)->private_data;
64 }
65 
66 static ssize_t disksize_show(struct device *dev,
67 		struct device_attribute *attr, char *buf)
68 {
69 	struct zram *zram = dev_to_zram(dev);
70 
71 	return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
72 }
73 
74 static ssize_t initstate_show(struct device *dev,
75 		struct device_attribute *attr, char *buf)
76 {
77 	u32 val;
78 	struct zram *zram = dev_to_zram(dev);
79 
80 	down_read(&zram->init_lock);
81 	val = init_done(zram);
82 	up_read(&zram->init_lock);
83 
84 	return scnprintf(buf, PAGE_SIZE, "%u\n", val);
85 }
86 
87 static ssize_t orig_data_size_show(struct device *dev,
88 		struct device_attribute *attr, char *buf)
89 {
90 	struct zram *zram = dev_to_zram(dev);
91 
92 	return scnprintf(buf, PAGE_SIZE, "%llu\n",
93 		(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
94 }
95 
96 static ssize_t mem_used_total_show(struct device *dev,
97 		struct device_attribute *attr, char *buf)
98 {
99 	u64 val = 0;
100 	struct zram *zram = dev_to_zram(dev);
101 
102 	down_read(&zram->init_lock);
103 	if (init_done(zram)) {
104 		struct zram_meta *meta = zram->meta;
105 		val = zs_get_total_pages(meta->mem_pool);
106 	}
107 	up_read(&zram->init_lock);
108 
109 	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
110 }
111 
112 static ssize_t max_comp_streams_show(struct device *dev,
113 		struct device_attribute *attr, char *buf)
114 {
115 	int val;
116 	struct zram *zram = dev_to_zram(dev);
117 
118 	down_read(&zram->init_lock);
119 	val = zram->max_comp_streams;
120 	up_read(&zram->init_lock);
121 
122 	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
123 }
124 
125 static ssize_t mem_limit_show(struct device *dev,
126 		struct device_attribute *attr, char *buf)
127 {
128 	u64 val;
129 	struct zram *zram = dev_to_zram(dev);
130 
131 	down_read(&zram->init_lock);
132 	val = zram->limit_pages;
133 	up_read(&zram->init_lock);
134 
135 	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
136 }
137 
138 static ssize_t mem_limit_store(struct device *dev,
139 		struct device_attribute *attr, const char *buf, size_t len)
140 {
141 	u64 limit;
142 	char *tmp;
143 	struct zram *zram = dev_to_zram(dev);
144 
145 	limit = memparse(buf, &tmp);
146 	if (buf == tmp) /* no chars parsed, invalid input */
147 		return -EINVAL;
148 
149 	down_write(&zram->init_lock);
150 	zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
151 	up_write(&zram->init_lock);
152 
153 	return len;
154 }
155 
156 static ssize_t mem_used_max_show(struct device *dev,
157 		struct device_attribute *attr, char *buf)
158 {
159 	u64 val = 0;
160 	struct zram *zram = dev_to_zram(dev);
161 
162 	down_read(&zram->init_lock);
163 	if (init_done(zram))
164 		val = atomic_long_read(&zram->stats.max_used_pages);
165 	up_read(&zram->init_lock);
166 
167 	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
168 }
169 
170 static ssize_t mem_used_max_store(struct device *dev,
171 		struct device_attribute *attr, const char *buf, size_t len)
172 {
173 	int err;
174 	unsigned long val;
175 	struct zram *zram = dev_to_zram(dev);
176 
177 	err = kstrtoul(buf, 10, &val);
178 	if (err || val != 0)
179 		return -EINVAL;
180 
181 	down_read(&zram->init_lock);
182 	if (init_done(zram)) {
183 		struct zram_meta *meta = zram->meta;
184 		atomic_long_set(&zram->stats.max_used_pages,
185 				zs_get_total_pages(meta->mem_pool));
186 	}
187 	up_read(&zram->init_lock);
188 
189 	return len;
190 }
191 
192 static ssize_t max_comp_streams_store(struct device *dev,
193 		struct device_attribute *attr, const char *buf, size_t len)
194 {
195 	int num;
196 	struct zram *zram = dev_to_zram(dev);
197 	int ret;
198 
199 	ret = kstrtoint(buf, 0, &num);
200 	if (ret < 0)
201 		return ret;
202 	if (num < 1)
203 		return -EINVAL;
204 
205 	down_write(&zram->init_lock);
206 	if (init_done(zram)) {
207 		if (!zcomp_set_max_streams(zram->comp, num)) {
208 			pr_info("Cannot change max compression streams\n");
209 			ret = -EINVAL;
210 			goto out;
211 		}
212 	}
213 
214 	zram->max_comp_streams = num;
215 	ret = len;
216 out:
217 	up_write(&zram->init_lock);
218 	return ret;
219 }
220 
221 static ssize_t comp_algorithm_show(struct device *dev,
222 		struct device_attribute *attr, char *buf)
223 {
224 	size_t sz;
225 	struct zram *zram = dev_to_zram(dev);
226 
227 	down_read(&zram->init_lock);
228 	sz = zcomp_available_show(zram->compressor, buf);
229 	up_read(&zram->init_lock);
230 
231 	return sz;
232 }
233 
234 static ssize_t comp_algorithm_store(struct device *dev,
235 		struct device_attribute *attr, const char *buf, size_t len)
236 {
237 	struct zram *zram = dev_to_zram(dev);
238 	down_write(&zram->init_lock);
239 	if (init_done(zram)) {
240 		up_write(&zram->init_lock);
241 		pr_info("Can't change algorithm for initialized device\n");
242 		return -EBUSY;
243 	}
244 	strlcpy(zram->compressor, buf, sizeof(zram->compressor));
245 	up_write(&zram->init_lock);
246 	return len;
247 }
248 
249 /* flag operations needs meta->tb_lock */
250 static int zram_test_flag(struct zram_meta *meta, u32 index,
251 			enum zram_pageflags flag)
252 {
253 	return meta->table[index].value & BIT(flag);
254 }
255 
256 static void zram_set_flag(struct zram_meta *meta, u32 index,
257 			enum zram_pageflags flag)
258 {
259 	meta->table[index].value |= BIT(flag);
260 }
261 
262 static void zram_clear_flag(struct zram_meta *meta, u32 index,
263 			enum zram_pageflags flag)
264 {
265 	meta->table[index].value &= ~BIT(flag);
266 }
267 
268 static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
269 {
270 	return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
271 }
272 
273 static void zram_set_obj_size(struct zram_meta *meta,
274 					u32 index, size_t size)
275 {
276 	unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
277 
278 	meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
279 }
280 
281 static inline int is_partial_io(struct bio_vec *bvec)
282 {
283 	return bvec->bv_len != PAGE_SIZE;
284 }
285 
286 /*
287  * Check if request is within bounds and aligned on zram logical blocks.
288  */
289 static inline int valid_io_request(struct zram *zram,
290 		sector_t start, unsigned int size)
291 {
292 	u64 end, bound;
293 
294 	/* unaligned request */
295 	if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
296 		return 0;
297 	if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
298 		return 0;
299 
300 	end = start + (size >> SECTOR_SHIFT);
301 	bound = zram->disksize >> SECTOR_SHIFT;
302 	/* out of range range */
303 	if (unlikely(start >= bound || end > bound || start > end))
304 		return 0;
305 
306 	/* I/O request is valid */
307 	return 1;
308 }
309 
310 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
311 {
312 	size_t num_pages = disksize >> PAGE_SHIFT;
313 	size_t index;
314 
315 	/* Free all pages that are still in this zram device */
316 	for (index = 0; index < num_pages; index++) {
317 		unsigned long handle = meta->table[index].handle;
318 
319 		if (!handle)
320 			continue;
321 
322 		zs_free(meta->mem_pool, handle);
323 	}
324 
325 	zs_destroy_pool(meta->mem_pool);
326 	vfree(meta->table);
327 	kfree(meta);
328 }
329 
330 static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
331 {
332 	size_t num_pages;
333 	char pool_name[8];
334 	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
335 
336 	if (!meta)
337 		return NULL;
338 
339 	num_pages = disksize >> PAGE_SHIFT;
340 	meta->table = vzalloc(num_pages * sizeof(*meta->table));
341 	if (!meta->table) {
342 		pr_err("Error allocating zram address table\n");
343 		goto out_error;
344 	}
345 
346 	snprintf(pool_name, sizeof(pool_name), "zram%d", device_id);
347 	meta->mem_pool = zs_create_pool(pool_name, GFP_NOIO | __GFP_HIGHMEM);
348 	if (!meta->mem_pool) {
349 		pr_err("Error creating memory pool\n");
350 		goto out_error;
351 	}
352 
353 	return meta;
354 
355 out_error:
356 	vfree(meta->table);
357 	kfree(meta);
358 	return NULL;
359 }
360 
361 static inline bool zram_meta_get(struct zram *zram)
362 {
363 	if (atomic_inc_not_zero(&zram->refcount))
364 		return true;
365 	return false;
366 }
367 
368 static inline void zram_meta_put(struct zram *zram)
369 {
370 	atomic_dec(&zram->refcount);
371 }
372 
373 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
374 {
375 	if (*offset + bvec->bv_len >= PAGE_SIZE)
376 		(*index)++;
377 	*offset = (*offset + bvec->bv_len) % PAGE_SIZE;
378 }
379 
380 static int page_zero_filled(void *ptr)
381 {
382 	unsigned int pos;
383 	unsigned long *page;
384 
385 	page = (unsigned long *)ptr;
386 
387 	for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
388 		if (page[pos])
389 			return 0;
390 	}
391 
392 	return 1;
393 }
394 
395 static void handle_zero_page(struct bio_vec *bvec)
396 {
397 	struct page *page = bvec->bv_page;
398 	void *user_mem;
399 
400 	user_mem = kmap_atomic(page);
401 	if (is_partial_io(bvec))
402 		memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
403 	else
404 		clear_page(user_mem);
405 	kunmap_atomic(user_mem);
406 
407 	flush_dcache_page(page);
408 }
409 
410 
411 /*
412  * To protect concurrent access to the same index entry,
413  * caller should hold this table index entry's bit_spinlock to
414  * indicate this index entry is accessing.
415  */
416 static void zram_free_page(struct zram *zram, size_t index)
417 {
418 	struct zram_meta *meta = zram->meta;
419 	unsigned long handle = meta->table[index].handle;
420 
421 	if (unlikely(!handle)) {
422 		/*
423 		 * No memory is allocated for zero filled pages.
424 		 * Simply clear zero page flag.
425 		 */
426 		if (zram_test_flag(meta, index, ZRAM_ZERO)) {
427 			zram_clear_flag(meta, index, ZRAM_ZERO);
428 			atomic64_dec(&zram->stats.zero_pages);
429 		}
430 		return;
431 	}
432 
433 	zs_free(meta->mem_pool, handle);
434 
435 	atomic64_sub(zram_get_obj_size(meta, index),
436 			&zram->stats.compr_data_size);
437 	atomic64_dec(&zram->stats.pages_stored);
438 
439 	meta->table[index].handle = 0;
440 	zram_set_obj_size(meta, index, 0);
441 }
442 
443 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
444 {
445 	int ret = 0;
446 	unsigned char *cmem;
447 	struct zram_meta *meta = zram->meta;
448 	unsigned long handle;
449 	size_t size;
450 
451 	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
452 	handle = meta->table[index].handle;
453 	size = zram_get_obj_size(meta, index);
454 
455 	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
456 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
457 		clear_page(mem);
458 		return 0;
459 	}
460 
461 	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
462 	if (size == PAGE_SIZE)
463 		copy_page(mem, cmem);
464 	else
465 		ret = zcomp_decompress(zram->comp, cmem, size, mem);
466 	zs_unmap_object(meta->mem_pool, handle);
467 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
468 
469 	/* Should NEVER happen. Return bio error if it does. */
470 	if (unlikely(ret)) {
471 		pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
472 		return ret;
473 	}
474 
475 	return 0;
476 }
477 
478 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
479 			  u32 index, int offset)
480 {
481 	int ret;
482 	struct page *page;
483 	unsigned char *user_mem, *uncmem = NULL;
484 	struct zram_meta *meta = zram->meta;
485 	page = bvec->bv_page;
486 
487 	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
488 	if (unlikely(!meta->table[index].handle) ||
489 			zram_test_flag(meta, index, ZRAM_ZERO)) {
490 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
491 		handle_zero_page(bvec);
492 		return 0;
493 	}
494 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
495 
496 	if (is_partial_io(bvec))
497 		/* Use  a temporary buffer to decompress the page */
498 		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
499 
500 	user_mem = kmap_atomic(page);
501 	if (!is_partial_io(bvec))
502 		uncmem = user_mem;
503 
504 	if (!uncmem) {
505 		pr_info("Unable to allocate temp memory\n");
506 		ret = -ENOMEM;
507 		goto out_cleanup;
508 	}
509 
510 	ret = zram_decompress_page(zram, uncmem, index);
511 	/* Should NEVER happen. Return bio error if it does. */
512 	if (unlikely(ret))
513 		goto out_cleanup;
514 
515 	if (is_partial_io(bvec))
516 		memcpy(user_mem + bvec->bv_offset, uncmem + offset,
517 				bvec->bv_len);
518 
519 	flush_dcache_page(page);
520 	ret = 0;
521 out_cleanup:
522 	kunmap_atomic(user_mem);
523 	if (is_partial_io(bvec))
524 		kfree(uncmem);
525 	return ret;
526 }
527 
528 static inline void update_used_max(struct zram *zram,
529 					const unsigned long pages)
530 {
531 	unsigned long old_max, cur_max;
532 
533 	old_max = atomic_long_read(&zram->stats.max_used_pages);
534 
535 	do {
536 		cur_max = old_max;
537 		if (pages > cur_max)
538 			old_max = atomic_long_cmpxchg(
539 				&zram->stats.max_used_pages, cur_max, pages);
540 	} while (old_max != cur_max);
541 }
542 
543 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
544 			   int offset)
545 {
546 	int ret = 0;
547 	size_t clen;
548 	unsigned long handle;
549 	struct page *page;
550 	unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
551 	struct zram_meta *meta = zram->meta;
552 	struct zcomp_strm *zstrm;
553 	bool locked = false;
554 	unsigned long alloced_pages;
555 
556 	page = bvec->bv_page;
557 	if (is_partial_io(bvec)) {
558 		/*
559 		 * This is a partial IO. We need to read the full page
560 		 * before to write the changes.
561 		 */
562 		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
563 		if (!uncmem) {
564 			ret = -ENOMEM;
565 			goto out;
566 		}
567 		ret = zram_decompress_page(zram, uncmem, index);
568 		if (ret)
569 			goto out;
570 	}
571 
572 	zstrm = zcomp_strm_find(zram->comp);
573 	locked = true;
574 	user_mem = kmap_atomic(page);
575 
576 	if (is_partial_io(bvec)) {
577 		memcpy(uncmem + offset, user_mem + bvec->bv_offset,
578 		       bvec->bv_len);
579 		kunmap_atomic(user_mem);
580 		user_mem = NULL;
581 	} else {
582 		uncmem = user_mem;
583 	}
584 
585 	if (page_zero_filled(uncmem)) {
586 		if (user_mem)
587 			kunmap_atomic(user_mem);
588 		/* Free memory associated with this sector now. */
589 		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
590 		zram_free_page(zram, index);
591 		zram_set_flag(meta, index, ZRAM_ZERO);
592 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
593 
594 		atomic64_inc(&zram->stats.zero_pages);
595 		ret = 0;
596 		goto out;
597 	}
598 
599 	ret = zcomp_compress(zram->comp, zstrm, uncmem, &clen);
600 	if (!is_partial_io(bvec)) {
601 		kunmap_atomic(user_mem);
602 		user_mem = NULL;
603 		uncmem = NULL;
604 	}
605 
606 	if (unlikely(ret)) {
607 		pr_err("Compression failed! err=%d\n", ret);
608 		goto out;
609 	}
610 	src = zstrm->buffer;
611 	if (unlikely(clen > max_zpage_size)) {
612 		clen = PAGE_SIZE;
613 		if (is_partial_io(bvec))
614 			src = uncmem;
615 	}
616 
617 	handle = zs_malloc(meta->mem_pool, clen);
618 	if (!handle) {
619 		pr_info("Error allocating memory for compressed page: %u, size=%zu\n",
620 			index, clen);
621 		ret = -ENOMEM;
622 		goto out;
623 	}
624 
625 	alloced_pages = zs_get_total_pages(meta->mem_pool);
626 	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
627 		zs_free(meta->mem_pool, handle);
628 		ret = -ENOMEM;
629 		goto out;
630 	}
631 
632 	update_used_max(zram, alloced_pages);
633 
634 	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
635 
636 	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
637 		src = kmap_atomic(page);
638 		copy_page(cmem, src);
639 		kunmap_atomic(src);
640 	} else {
641 		memcpy(cmem, src, clen);
642 	}
643 
644 	zcomp_strm_release(zram->comp, zstrm);
645 	locked = false;
646 	zs_unmap_object(meta->mem_pool, handle);
647 
648 	/*
649 	 * Free memory associated with this sector
650 	 * before overwriting unused sectors.
651 	 */
652 	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
653 	zram_free_page(zram, index);
654 
655 	meta->table[index].handle = handle;
656 	zram_set_obj_size(meta, index, clen);
657 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
658 
659 	/* Update stats */
660 	atomic64_add(clen, &zram->stats.compr_data_size);
661 	atomic64_inc(&zram->stats.pages_stored);
662 out:
663 	if (locked)
664 		zcomp_strm_release(zram->comp, zstrm);
665 	if (is_partial_io(bvec))
666 		kfree(uncmem);
667 	return ret;
668 }
669 
670 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
671 			int offset, int rw)
672 {
673 	int ret;
674 
675 	if (rw == READ) {
676 		atomic64_inc(&zram->stats.num_reads);
677 		ret = zram_bvec_read(zram, bvec, index, offset);
678 	} else {
679 		atomic64_inc(&zram->stats.num_writes);
680 		ret = zram_bvec_write(zram, bvec, index, offset);
681 	}
682 
683 	if (unlikely(ret)) {
684 		if (rw == READ)
685 			atomic64_inc(&zram->stats.failed_reads);
686 		else
687 			atomic64_inc(&zram->stats.failed_writes);
688 	}
689 
690 	return ret;
691 }
692 
693 /*
694  * zram_bio_discard - handler on discard request
695  * @index: physical block index in PAGE_SIZE units
696  * @offset: byte offset within physical block
697  */
698 static void zram_bio_discard(struct zram *zram, u32 index,
699 			     int offset, struct bio *bio)
700 {
701 	size_t n = bio->bi_iter.bi_size;
702 	struct zram_meta *meta = zram->meta;
703 
704 	/*
705 	 * zram manages data in physical block size units. Because logical block
706 	 * size isn't identical with physical block size on some arch, we
707 	 * could get a discard request pointing to a specific offset within a
708 	 * certain physical block.  Although we can handle this request by
709 	 * reading that physiclal block and decompressing and partially zeroing
710 	 * and re-compressing and then re-storing it, this isn't reasonable
711 	 * because our intent with a discard request is to save memory.  So
712 	 * skipping this logical block is appropriate here.
713 	 */
714 	if (offset) {
715 		if (n <= (PAGE_SIZE - offset))
716 			return;
717 
718 		n -= (PAGE_SIZE - offset);
719 		index++;
720 	}
721 
722 	while (n >= PAGE_SIZE) {
723 		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
724 		zram_free_page(zram, index);
725 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
726 		atomic64_inc(&zram->stats.notify_free);
727 		index++;
728 		n -= PAGE_SIZE;
729 	}
730 }
731 
732 static void zram_reset_device(struct zram *zram)
733 {
734 	struct zram_meta *meta;
735 	struct zcomp *comp;
736 	u64 disksize;
737 
738 	down_write(&zram->init_lock);
739 
740 	zram->limit_pages = 0;
741 
742 	if (!init_done(zram)) {
743 		up_write(&zram->init_lock);
744 		return;
745 	}
746 
747 	meta = zram->meta;
748 	comp = zram->comp;
749 	disksize = zram->disksize;
750 	/*
751 	 * Refcount will go down to 0 eventually and r/w handler
752 	 * cannot handle further I/O so it will bail out by
753 	 * check zram_meta_get.
754 	 */
755 	zram_meta_put(zram);
756 	/*
757 	 * We want to free zram_meta in process context to avoid
758 	 * deadlock between reclaim path and any other locks.
759 	 */
760 	wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
761 
762 	/* Reset stats */
763 	memset(&zram->stats, 0, sizeof(zram->stats));
764 	zram->disksize = 0;
765 	zram->max_comp_streams = 1;
766 	set_capacity(zram->disk, 0);
767 
768 	up_write(&zram->init_lock);
769 	/* I/O operation under all of CPU are done so let's free */
770 	zram_meta_free(meta, disksize);
771 	zcomp_destroy(comp);
772 }
773 
774 static ssize_t disksize_store(struct device *dev,
775 		struct device_attribute *attr, const char *buf, size_t len)
776 {
777 	u64 disksize;
778 	struct zcomp *comp;
779 	struct zram_meta *meta;
780 	struct zram *zram = dev_to_zram(dev);
781 	int err;
782 
783 	disksize = memparse(buf, NULL);
784 	if (!disksize)
785 		return -EINVAL;
786 
787 	disksize = PAGE_ALIGN(disksize);
788 	meta = zram_meta_alloc(zram->disk->first_minor, disksize);
789 	if (!meta)
790 		return -ENOMEM;
791 
792 	comp = zcomp_create(zram->compressor, zram->max_comp_streams);
793 	if (IS_ERR(comp)) {
794 		pr_info("Cannot initialise %s compressing backend\n",
795 				zram->compressor);
796 		err = PTR_ERR(comp);
797 		goto out_free_meta;
798 	}
799 
800 	down_write(&zram->init_lock);
801 	if (init_done(zram)) {
802 		pr_info("Cannot change disksize for initialized device\n");
803 		err = -EBUSY;
804 		goto out_destroy_comp;
805 	}
806 
807 	init_waitqueue_head(&zram->io_done);
808 	atomic_set(&zram->refcount, 1);
809 	zram->meta = meta;
810 	zram->comp = comp;
811 	zram->disksize = disksize;
812 	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
813 	up_write(&zram->init_lock);
814 
815 	/*
816 	 * Revalidate disk out of the init_lock to avoid lockdep splat.
817 	 * It's okay because disk's capacity is protected by init_lock
818 	 * so that revalidate_disk always sees up-to-date capacity.
819 	 */
820 	revalidate_disk(zram->disk);
821 
822 	return len;
823 
824 out_destroy_comp:
825 	up_write(&zram->init_lock);
826 	zcomp_destroy(comp);
827 out_free_meta:
828 	zram_meta_free(meta, disksize);
829 	return err;
830 }
831 
832 static ssize_t reset_store(struct device *dev,
833 		struct device_attribute *attr, const char *buf, size_t len)
834 {
835 	int ret;
836 	unsigned short do_reset;
837 	struct zram *zram;
838 	struct block_device *bdev;
839 
840 	zram = dev_to_zram(dev);
841 	bdev = bdget_disk(zram->disk, 0);
842 
843 	if (!bdev)
844 		return -ENOMEM;
845 
846 	mutex_lock(&bdev->bd_mutex);
847 	/* Do not reset an active device! */
848 	if (bdev->bd_openers) {
849 		ret = -EBUSY;
850 		goto out;
851 	}
852 
853 	ret = kstrtou16(buf, 10, &do_reset);
854 	if (ret)
855 		goto out;
856 
857 	if (!do_reset) {
858 		ret = -EINVAL;
859 		goto out;
860 	}
861 
862 	/* Make sure all pending I/O is finished */
863 	fsync_bdev(bdev);
864 	zram_reset_device(zram);
865 
866 	mutex_unlock(&bdev->bd_mutex);
867 	revalidate_disk(zram->disk);
868 	bdput(bdev);
869 
870 	return len;
871 
872 out:
873 	mutex_unlock(&bdev->bd_mutex);
874 	bdput(bdev);
875 	return ret;
876 }
877 
878 static void __zram_make_request(struct zram *zram, struct bio *bio)
879 {
880 	int offset, rw;
881 	u32 index;
882 	struct bio_vec bvec;
883 	struct bvec_iter iter;
884 
885 	index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
886 	offset = (bio->bi_iter.bi_sector &
887 		  (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
888 
889 	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
890 		zram_bio_discard(zram, index, offset, bio);
891 		bio_endio(bio, 0);
892 		return;
893 	}
894 
895 	rw = bio_data_dir(bio);
896 	bio_for_each_segment(bvec, bio, iter) {
897 		int max_transfer_size = PAGE_SIZE - offset;
898 
899 		if (bvec.bv_len > max_transfer_size) {
900 			/*
901 			 * zram_bvec_rw() can only make operation on a single
902 			 * zram page. Split the bio vector.
903 			 */
904 			struct bio_vec bv;
905 
906 			bv.bv_page = bvec.bv_page;
907 			bv.bv_len = max_transfer_size;
908 			bv.bv_offset = bvec.bv_offset;
909 
910 			if (zram_bvec_rw(zram, &bv, index, offset, rw) < 0)
911 				goto out;
912 
913 			bv.bv_len = bvec.bv_len - max_transfer_size;
914 			bv.bv_offset += max_transfer_size;
915 			if (zram_bvec_rw(zram, &bv, index + 1, 0, rw) < 0)
916 				goto out;
917 		} else
918 			if (zram_bvec_rw(zram, &bvec, index, offset, rw) < 0)
919 				goto out;
920 
921 		update_position(&index, &offset, &bvec);
922 	}
923 
924 	set_bit(BIO_UPTODATE, &bio->bi_flags);
925 	bio_endio(bio, 0);
926 	return;
927 
928 out:
929 	bio_io_error(bio);
930 }
931 
932 /*
933  * Handler function for all zram I/O requests.
934  */
935 static void zram_make_request(struct request_queue *queue, struct bio *bio)
936 {
937 	struct zram *zram = queue->queuedata;
938 
939 	if (unlikely(!zram_meta_get(zram)))
940 		goto error;
941 
942 	if (!valid_io_request(zram, bio->bi_iter.bi_sector,
943 					bio->bi_iter.bi_size)) {
944 		atomic64_inc(&zram->stats.invalid_io);
945 		goto put_zram;
946 	}
947 
948 	__zram_make_request(zram, bio);
949 	zram_meta_put(zram);
950 	return;
951 put_zram:
952 	zram_meta_put(zram);
953 error:
954 	bio_io_error(bio);
955 }
956 
957 static void zram_slot_free_notify(struct block_device *bdev,
958 				unsigned long index)
959 {
960 	struct zram *zram;
961 	struct zram_meta *meta;
962 
963 	zram = bdev->bd_disk->private_data;
964 	meta = zram->meta;
965 
966 	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
967 	zram_free_page(zram, index);
968 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
969 	atomic64_inc(&zram->stats.notify_free);
970 }
971 
972 static int zram_rw_page(struct block_device *bdev, sector_t sector,
973 		       struct page *page, int rw)
974 {
975 	int offset, err = -EIO;
976 	u32 index;
977 	struct zram *zram;
978 	struct bio_vec bv;
979 
980 	zram = bdev->bd_disk->private_data;
981 	if (unlikely(!zram_meta_get(zram)))
982 		goto out;
983 
984 	if (!valid_io_request(zram, sector, PAGE_SIZE)) {
985 		atomic64_inc(&zram->stats.invalid_io);
986 		err = -EINVAL;
987 		goto put_zram;
988 	}
989 
990 	index = sector >> SECTORS_PER_PAGE_SHIFT;
991 	offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
992 
993 	bv.bv_page = page;
994 	bv.bv_len = PAGE_SIZE;
995 	bv.bv_offset = 0;
996 
997 	err = zram_bvec_rw(zram, &bv, index, offset, rw);
998 put_zram:
999 	zram_meta_put(zram);
1000 out:
1001 	/*
1002 	 * If I/O fails, just return error(ie, non-zero) without
1003 	 * calling page_endio.
1004 	 * It causes resubmit the I/O with bio request by upper functions
1005 	 * of rw_page(e.g., swap_readpage, __swap_writepage) and
1006 	 * bio->bi_end_io does things to handle the error
1007 	 * (e.g., SetPageError, set_page_dirty and extra works).
1008 	 */
1009 	if (err == 0)
1010 		page_endio(page, rw, 0);
1011 	return err;
1012 }
1013 
1014 static const struct block_device_operations zram_devops = {
1015 	.swap_slot_free_notify = zram_slot_free_notify,
1016 	.rw_page = zram_rw_page,
1017 	.owner = THIS_MODULE
1018 };
1019 
1020 static DEVICE_ATTR_RW(disksize);
1021 static DEVICE_ATTR_RO(initstate);
1022 static DEVICE_ATTR_WO(reset);
1023 static DEVICE_ATTR_RO(orig_data_size);
1024 static DEVICE_ATTR_RO(mem_used_total);
1025 static DEVICE_ATTR_RW(mem_limit);
1026 static DEVICE_ATTR_RW(mem_used_max);
1027 static DEVICE_ATTR_RW(max_comp_streams);
1028 static DEVICE_ATTR_RW(comp_algorithm);
1029 
1030 ZRAM_ATTR_RO(num_reads);
1031 ZRAM_ATTR_RO(num_writes);
1032 ZRAM_ATTR_RO(failed_reads);
1033 ZRAM_ATTR_RO(failed_writes);
1034 ZRAM_ATTR_RO(invalid_io);
1035 ZRAM_ATTR_RO(notify_free);
1036 ZRAM_ATTR_RO(zero_pages);
1037 ZRAM_ATTR_RO(compr_data_size);
1038 
1039 static struct attribute *zram_disk_attrs[] = {
1040 	&dev_attr_disksize.attr,
1041 	&dev_attr_initstate.attr,
1042 	&dev_attr_reset.attr,
1043 	&dev_attr_num_reads.attr,
1044 	&dev_attr_num_writes.attr,
1045 	&dev_attr_failed_reads.attr,
1046 	&dev_attr_failed_writes.attr,
1047 	&dev_attr_invalid_io.attr,
1048 	&dev_attr_notify_free.attr,
1049 	&dev_attr_zero_pages.attr,
1050 	&dev_attr_orig_data_size.attr,
1051 	&dev_attr_compr_data_size.attr,
1052 	&dev_attr_mem_used_total.attr,
1053 	&dev_attr_mem_limit.attr,
1054 	&dev_attr_mem_used_max.attr,
1055 	&dev_attr_max_comp_streams.attr,
1056 	&dev_attr_comp_algorithm.attr,
1057 	NULL,
1058 };
1059 
1060 static struct attribute_group zram_disk_attr_group = {
1061 	.attrs = zram_disk_attrs,
1062 };
1063 
1064 static int create_device(struct zram *zram, int device_id)
1065 {
1066 	struct request_queue *queue;
1067 	int ret = -ENOMEM;
1068 
1069 	init_rwsem(&zram->init_lock);
1070 
1071 	queue = blk_alloc_queue(GFP_KERNEL);
1072 	if (!queue) {
1073 		pr_err("Error allocating disk queue for device %d\n",
1074 			device_id);
1075 		goto out;
1076 	}
1077 
1078 	blk_queue_make_request(queue, zram_make_request);
1079 
1080 	 /* gendisk structure */
1081 	zram->disk = alloc_disk(1);
1082 	if (!zram->disk) {
1083 		pr_warn("Error allocating disk structure for device %d\n",
1084 			device_id);
1085 		goto out_free_queue;
1086 	}
1087 
1088 	zram->disk->major = zram_major;
1089 	zram->disk->first_minor = device_id;
1090 	zram->disk->fops = &zram_devops;
1091 	zram->disk->queue = queue;
1092 	zram->disk->queue->queuedata = zram;
1093 	zram->disk->private_data = zram;
1094 	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
1095 
1096 	/* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
1097 	set_capacity(zram->disk, 0);
1098 	/* zram devices sort of resembles non-rotational disks */
1099 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
1100 	queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
1101 	/*
1102 	 * To ensure that we always get PAGE_SIZE aligned
1103 	 * and n*PAGE_SIZED sized I/O requests.
1104 	 */
1105 	blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
1106 	blk_queue_logical_block_size(zram->disk->queue,
1107 					ZRAM_LOGICAL_BLOCK_SIZE);
1108 	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
1109 	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
1110 	zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
1111 	zram->disk->queue->limits.max_discard_sectors = UINT_MAX;
1112 	/*
1113 	 * zram_bio_discard() will clear all logical blocks if logical block
1114 	 * size is identical with physical block size(PAGE_SIZE). But if it is
1115 	 * different, we will skip discarding some parts of logical blocks in
1116 	 * the part of the request range which isn't aligned to physical block
1117 	 * size.  So we can't ensure that all discarded logical blocks are
1118 	 * zeroed.
1119 	 */
1120 	if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
1121 		zram->disk->queue->limits.discard_zeroes_data = 1;
1122 	else
1123 		zram->disk->queue->limits.discard_zeroes_data = 0;
1124 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
1125 
1126 	add_disk(zram->disk);
1127 
1128 	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
1129 				&zram_disk_attr_group);
1130 	if (ret < 0) {
1131 		pr_warn("Error creating sysfs group");
1132 		goto out_free_disk;
1133 	}
1134 	strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
1135 	zram->meta = NULL;
1136 	zram->max_comp_streams = 1;
1137 	return 0;
1138 
1139 out_free_disk:
1140 	del_gendisk(zram->disk);
1141 	put_disk(zram->disk);
1142 out_free_queue:
1143 	blk_cleanup_queue(queue);
1144 out:
1145 	return ret;
1146 }
1147 
1148 static void destroy_devices(unsigned int nr)
1149 {
1150 	struct zram *zram;
1151 	unsigned int i;
1152 
1153 	for (i = 0; i < nr; i++) {
1154 		zram = &zram_devices[i];
1155 		/*
1156 		 * Remove sysfs first, so no one will perform a disksize
1157 		 * store while we destroy the devices
1158 		 */
1159 		sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
1160 				&zram_disk_attr_group);
1161 
1162 		zram_reset_device(zram);
1163 
1164 		blk_cleanup_queue(zram->disk->queue);
1165 		del_gendisk(zram->disk);
1166 		put_disk(zram->disk);
1167 	}
1168 
1169 	kfree(zram_devices);
1170 	unregister_blkdev(zram_major, "zram");
1171 	pr_info("Destroyed %u device(s)\n", nr);
1172 }
1173 
1174 static int __init zram_init(void)
1175 {
1176 	int ret, dev_id;
1177 
1178 	if (num_devices > max_num_devices) {
1179 		pr_warn("Invalid value for num_devices: %u\n",
1180 				num_devices);
1181 		return -EINVAL;
1182 	}
1183 
1184 	zram_major = register_blkdev(0, "zram");
1185 	if (zram_major <= 0) {
1186 		pr_warn("Unable to get major number\n");
1187 		return -EBUSY;
1188 	}
1189 
1190 	/* Allocate the device array and initialize each one */
1191 	zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
1192 	if (!zram_devices) {
1193 		unregister_blkdev(zram_major, "zram");
1194 		return -ENOMEM;
1195 	}
1196 
1197 	for (dev_id = 0; dev_id < num_devices; dev_id++) {
1198 		ret = create_device(&zram_devices[dev_id], dev_id);
1199 		if (ret)
1200 			goto out_error;
1201 	}
1202 
1203 	pr_info("Created %u device(s)\n", num_devices);
1204 	return 0;
1205 
1206 out_error:
1207 	destroy_devices(dev_id);
1208 	return ret;
1209 }
1210 
1211 static void __exit zram_exit(void)
1212 {
1213 	destroy_devices(num_devices);
1214 }
1215 
1216 module_init(zram_init);
1217 module_exit(zram_exit);
1218 
1219 module_param(num_devices, uint, 0);
1220 MODULE_PARM_DESC(num_devices, "Number of zram devices");
1221 
1222 MODULE_LICENSE("Dual BSD/GPL");
1223 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
1224 MODULE_DESCRIPTION("Compressed RAM Block Device");
1225