1 /*
2  * Copyright (C) 2009-2011 Red Hat, Inc.
3  *
4  * Author: Mikulas Patocka <mpatocka@redhat.com>
5  *
6  * This file is released under the GPL.
7  */
8 
9 #include <linux/dm-bufio.h>
10 
11 #include <linux/device-mapper.h>
12 #include <linux/dm-io.h>
13 #include <linux/slab.h>
14 #include <linux/sched/mm.h>
15 #include <linux/jiffies.h>
16 #include <linux/vmalloc.h>
17 #include <linux/shrinker.h>
18 #include <linux/module.h>
19 #include <linux/rbtree.h>
20 #include <linux/stacktrace.h>
21 #include <linux/jump_label.h>
22 
23 #define DM_MSG_PREFIX "bufio"
24 
25 /*
26  * Memory management policy:
27  *	Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
28  *	or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
29  *	Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
30  *	Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
31  *	dirty buffers.
32  */
33 #define DM_BUFIO_MIN_BUFFERS		8
34 
35 #define DM_BUFIO_MEMORY_PERCENT		2
36 #define DM_BUFIO_VMALLOC_PERCENT	25
37 #define DM_BUFIO_WRITEBACK_RATIO	3
38 #define DM_BUFIO_LOW_WATERMARK_RATIO	16
39 
40 /*
41  * Check buffer ages in this interval (seconds)
42  */
43 #define DM_BUFIO_WORK_TIMER_SECS	30
44 
45 /*
46  * Free buffers when they are older than this (seconds)
47  */
48 #define DM_BUFIO_DEFAULT_AGE_SECS	300
49 
50 /*
51  * The nr of bytes of cached data to keep around.
52  */
53 #define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
54 
55 /*
56  * Align buffer writes to this boundary.
57  * Tests show that SSDs have the highest IOPS when using 4k writes.
58  */
59 #define DM_BUFIO_WRITE_ALIGN		4096
60 
61 /*
62  * dm_buffer->list_mode
63  */
64 #define LIST_CLEAN	0
65 #define LIST_DIRTY	1
66 #define LIST_SIZE	2
67 
68 /*
69  * Linking of buffers:
70  *	All buffers are linked to buffer_tree with their node field.
71  *
72  *	Clean buffers that are not being written (B_WRITING not set)
73  *	are linked to lru[LIST_CLEAN] with their lru_list field.
74  *
75  *	Dirty and clean buffers that are being written are linked to
76  *	lru[LIST_DIRTY] with their lru_list field. When the write
77  *	finishes, the buffer cannot be relinked immediately (because we
78  *	are in an interrupt context and relinking requires process
79  *	context), so some clean-not-writing buffers can be held on
80  *	dirty_lru too.  They are later added to lru in the process
81  *	context.
82  */
83 struct dm_bufio_client {
84 	struct mutex lock;
85 	spinlock_t spinlock;
86 	bool no_sleep;
87 
88 	struct list_head lru[LIST_SIZE];
89 	unsigned long n_buffers[LIST_SIZE];
90 
91 	struct block_device *bdev;
92 	unsigned block_size;
93 	s8 sectors_per_block_bits;
94 	void (*alloc_callback)(struct dm_buffer *);
95 	void (*write_callback)(struct dm_buffer *);
96 	struct kmem_cache *slab_buffer;
97 	struct kmem_cache *slab_cache;
98 	struct dm_io_client *dm_io;
99 
100 	struct list_head reserved_buffers;
101 	unsigned need_reserved_buffers;
102 
103 	unsigned minimum_buffers;
104 
105 	struct rb_root buffer_tree;
106 	wait_queue_head_t free_buffer_wait;
107 
108 	sector_t start;
109 
110 	int async_write_error;
111 
112 	struct list_head client_list;
113 
114 	struct shrinker shrinker;
115 	struct work_struct shrink_work;
116 	atomic_long_t need_shrink;
117 };
118 
119 /*
120  * Buffer state bits.
121  */
122 #define B_READING	0
123 #define B_WRITING	1
124 #define B_DIRTY		2
125 
126 /*
127  * Describes how the block was allocated:
128  * kmem_cache_alloc(), __get_free_pages() or vmalloc().
129  * See the comment at alloc_buffer_data.
130  */
131 enum data_mode {
132 	DATA_MODE_SLAB = 0,
133 	DATA_MODE_GET_FREE_PAGES = 1,
134 	DATA_MODE_VMALLOC = 2,
135 	DATA_MODE_LIMIT = 3
136 };
137 
138 struct dm_buffer {
139 	struct rb_node node;
140 	struct list_head lru_list;
141 	struct list_head global_list;
142 	sector_t block;
143 	void *data;
144 	unsigned char data_mode;		/* DATA_MODE_* */
145 	unsigned char list_mode;		/* LIST_* */
146 	blk_status_t read_error;
147 	blk_status_t write_error;
148 	unsigned accessed;
149 	unsigned hold_count;
150 	unsigned long state;
151 	unsigned long last_accessed;
152 	unsigned dirty_start;
153 	unsigned dirty_end;
154 	unsigned write_start;
155 	unsigned write_end;
156 	struct dm_bufio_client *c;
157 	struct list_head write_list;
158 	void (*end_io)(struct dm_buffer *, blk_status_t);
159 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
160 #define MAX_STACK 10
161 	unsigned int stack_len;
162 	unsigned long stack_entries[MAX_STACK];
163 #endif
164 };
165 
166 static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
167 
168 /*----------------------------------------------------------------*/
169 
170 #define dm_bufio_in_request()	(!!current->bio_list)
171 
dm_bufio_lock(struct dm_bufio_client * c)172 static void dm_bufio_lock(struct dm_bufio_client *c)
173 {
174 	if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
175 		spin_lock_bh(&c->spinlock);
176 	else
177 		mutex_lock_nested(&c->lock, dm_bufio_in_request());
178 }
179 
dm_bufio_trylock(struct dm_bufio_client * c)180 static int dm_bufio_trylock(struct dm_bufio_client *c)
181 {
182 	if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
183 		return spin_trylock_bh(&c->spinlock);
184 	else
185 		return mutex_trylock(&c->lock);
186 }
187 
dm_bufio_unlock(struct dm_bufio_client * c)188 static void dm_bufio_unlock(struct dm_bufio_client *c)
189 {
190 	if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
191 		spin_unlock_bh(&c->spinlock);
192 	else
193 		mutex_unlock(&c->lock);
194 }
195 
196 /*----------------------------------------------------------------*/
197 
198 /*
199  * Default cache size: available memory divided by the ratio.
200  */
201 static unsigned long dm_bufio_default_cache_size;
202 
203 /*
204  * Total cache size set by the user.
205  */
206 static unsigned long dm_bufio_cache_size;
207 
208 /*
209  * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
210  * at any time.  If it disagrees, the user has changed cache size.
211  */
212 static unsigned long dm_bufio_cache_size_latch;
213 
214 static DEFINE_SPINLOCK(global_spinlock);
215 
216 static LIST_HEAD(global_queue);
217 
218 static unsigned long global_num = 0;
219 
220 /*
221  * Buffers are freed after this timeout
222  */
223 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
224 static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
225 
226 static unsigned long dm_bufio_peak_allocated;
227 static unsigned long dm_bufio_allocated_kmem_cache;
228 static unsigned long dm_bufio_allocated_get_free_pages;
229 static unsigned long dm_bufio_allocated_vmalloc;
230 static unsigned long dm_bufio_current_allocated;
231 
232 /*----------------------------------------------------------------*/
233 
234 /*
235  * The current number of clients.
236  */
237 static int dm_bufio_client_count;
238 
239 /*
240  * The list of all clients.
241  */
242 static LIST_HEAD(dm_bufio_all_clients);
243 
244 /*
245  * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
246  */
247 static DEFINE_MUTEX(dm_bufio_clients_lock);
248 
249 static struct workqueue_struct *dm_bufio_wq;
250 static struct delayed_work dm_bufio_cleanup_old_work;
251 static struct work_struct dm_bufio_replacement_work;
252 
253 
254 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
buffer_record_stack(struct dm_buffer * b)255 static void buffer_record_stack(struct dm_buffer *b)
256 {
257 	b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
258 }
259 #endif
260 
261 /*----------------------------------------------------------------
262  * A red/black tree acts as an index for all the buffers.
263  *--------------------------------------------------------------*/
__find(struct dm_bufio_client * c,sector_t block)264 static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
265 {
266 	struct rb_node *n = c->buffer_tree.rb_node;
267 	struct dm_buffer *b;
268 
269 	while (n) {
270 		b = container_of(n, struct dm_buffer, node);
271 
272 		if (b->block == block)
273 			return b;
274 
275 		n = block < b->block ? n->rb_left : n->rb_right;
276 	}
277 
278 	return NULL;
279 }
280 
__find_next(struct dm_bufio_client * c,sector_t block)281 static struct dm_buffer *__find_next(struct dm_bufio_client *c, sector_t block)
282 {
283 	struct rb_node *n = c->buffer_tree.rb_node;
284 	struct dm_buffer *b;
285 	struct dm_buffer *best = NULL;
286 
287 	while (n) {
288 		b = container_of(n, struct dm_buffer, node);
289 
290 		if (b->block == block)
291 			return b;
292 
293 		if (block <= b->block) {
294 			n = n->rb_left;
295 			best = b;
296 		} else {
297 			n = n->rb_right;
298 		}
299 	}
300 
301 	return best;
302 }
303 
__insert(struct dm_bufio_client * c,struct dm_buffer * b)304 static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
305 {
306 	struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
307 	struct dm_buffer *found;
308 
309 	while (*new) {
310 		found = container_of(*new, struct dm_buffer, node);
311 
312 		if (found->block == b->block) {
313 			BUG_ON(found != b);
314 			return;
315 		}
316 
317 		parent = *new;
318 		new = b->block < found->block ?
319 			&found->node.rb_left : &found->node.rb_right;
320 	}
321 
322 	rb_link_node(&b->node, parent, new);
323 	rb_insert_color(&b->node, &c->buffer_tree);
324 }
325 
__remove(struct dm_bufio_client * c,struct dm_buffer * b)326 static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
327 {
328 	rb_erase(&b->node, &c->buffer_tree);
329 }
330 
331 /*----------------------------------------------------------------*/
332 
adjust_total_allocated(struct dm_buffer * b,bool unlink)333 static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
334 {
335 	unsigned char data_mode;
336 	long diff;
337 
338 	static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
339 		&dm_bufio_allocated_kmem_cache,
340 		&dm_bufio_allocated_get_free_pages,
341 		&dm_bufio_allocated_vmalloc,
342 	};
343 
344 	data_mode = b->data_mode;
345 	diff = (long)b->c->block_size;
346 	if (unlink)
347 		diff = -diff;
348 
349 	spin_lock(&global_spinlock);
350 
351 	*class_ptr[data_mode] += diff;
352 
353 	dm_bufio_current_allocated += diff;
354 
355 	if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
356 		dm_bufio_peak_allocated = dm_bufio_current_allocated;
357 
358 	b->accessed = 1;
359 
360 	if (!unlink) {
361 		list_add(&b->global_list, &global_queue);
362 		global_num++;
363 		if (dm_bufio_current_allocated > dm_bufio_cache_size)
364 			queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
365 	} else {
366 		list_del(&b->global_list);
367 		global_num--;
368 	}
369 
370 	spin_unlock(&global_spinlock);
371 }
372 
373 /*
374  * Change the number of clients and recalculate per-client limit.
375  */
__cache_size_refresh(void)376 static void __cache_size_refresh(void)
377 {
378 	BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
379 	BUG_ON(dm_bufio_client_count < 0);
380 
381 	dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
382 
383 	/*
384 	 * Use default if set to 0 and report the actual cache size used.
385 	 */
386 	if (!dm_bufio_cache_size_latch) {
387 		(void)cmpxchg(&dm_bufio_cache_size, 0,
388 			      dm_bufio_default_cache_size);
389 		dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
390 	}
391 }
392 
393 /*
394  * Allocating buffer data.
395  *
396  * Small buffers are allocated with kmem_cache, to use space optimally.
397  *
398  * For large buffers, we choose between get_free_pages and vmalloc.
399  * Each has advantages and disadvantages.
400  *
401  * __get_free_pages can randomly fail if the memory is fragmented.
402  * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
403  * as low as 128M) so using it for caching is not appropriate.
404  *
405  * If the allocation may fail we use __get_free_pages. Memory fragmentation
406  * won't have a fatal effect here, but it just causes flushes of some other
407  * buffers and more I/O will be performed. Don't use __get_free_pages if it
408  * always fails (i.e. order >= MAX_ORDER).
409  *
410  * If the allocation shouldn't fail we use __vmalloc. This is only for the
411  * initial reserve allocation, so there's no risk of wasting all vmalloc
412  * space.
413  */
alloc_buffer_data(struct dm_bufio_client * c,gfp_t gfp_mask,unsigned char * data_mode)414 static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
415 			       unsigned char *data_mode)
416 {
417 	if (unlikely(c->slab_cache != NULL)) {
418 		*data_mode = DATA_MODE_SLAB;
419 		return kmem_cache_alloc(c->slab_cache, gfp_mask);
420 	}
421 
422 	if (c->block_size <= KMALLOC_MAX_SIZE &&
423 	    gfp_mask & __GFP_NORETRY) {
424 		*data_mode = DATA_MODE_GET_FREE_PAGES;
425 		return (void *)__get_free_pages(gfp_mask,
426 						c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
427 	}
428 
429 	*data_mode = DATA_MODE_VMALLOC;
430 
431 	/*
432 	 * __vmalloc allocates the data pages and auxiliary structures with
433 	 * gfp_flags that were specified, but pagetables are always allocated
434 	 * with GFP_KERNEL, no matter what was specified as gfp_mask.
435 	 *
436 	 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
437 	 * all allocations done by this process (including pagetables) are done
438 	 * as if GFP_NOIO was specified.
439 	 */
440 	if (gfp_mask & __GFP_NORETRY) {
441 		unsigned noio_flag = memalloc_noio_save();
442 		void *ptr = __vmalloc(c->block_size, gfp_mask);
443 
444 		memalloc_noio_restore(noio_flag);
445 		return ptr;
446 	}
447 
448 	return __vmalloc(c->block_size, gfp_mask);
449 }
450 
451 /*
452  * Free buffer's data.
453  */
free_buffer_data(struct dm_bufio_client * c,void * data,unsigned char data_mode)454 static void free_buffer_data(struct dm_bufio_client *c,
455 			     void *data, unsigned char data_mode)
456 {
457 	switch (data_mode) {
458 	case DATA_MODE_SLAB:
459 		kmem_cache_free(c->slab_cache, data);
460 		break;
461 
462 	case DATA_MODE_GET_FREE_PAGES:
463 		free_pages((unsigned long)data,
464 			   c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
465 		break;
466 
467 	case DATA_MODE_VMALLOC:
468 		vfree(data);
469 		break;
470 
471 	default:
472 		DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
473 		       data_mode);
474 		BUG();
475 	}
476 }
477 
478 /*
479  * Allocate buffer and its data.
480  */
alloc_buffer(struct dm_bufio_client * c,gfp_t gfp_mask)481 static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
482 {
483 	struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
484 
485 	if (!b)
486 		return NULL;
487 
488 	b->c = c;
489 
490 	b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
491 	if (!b->data) {
492 		kmem_cache_free(c->slab_buffer, b);
493 		return NULL;
494 	}
495 
496 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
497 	b->stack_len = 0;
498 #endif
499 	return b;
500 }
501 
502 /*
503  * Free buffer and its data.
504  */
free_buffer(struct dm_buffer * b)505 static void free_buffer(struct dm_buffer *b)
506 {
507 	struct dm_bufio_client *c = b->c;
508 
509 	free_buffer_data(c, b->data, b->data_mode);
510 	kmem_cache_free(c->slab_buffer, b);
511 }
512 
513 /*
514  * Link buffer to the buffer tree and clean or dirty queue.
515  */
__link_buffer(struct dm_buffer * b,sector_t block,int dirty)516 static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
517 {
518 	struct dm_bufio_client *c = b->c;
519 
520 	c->n_buffers[dirty]++;
521 	b->block = block;
522 	b->list_mode = dirty;
523 	list_add(&b->lru_list, &c->lru[dirty]);
524 	__insert(b->c, b);
525 	b->last_accessed = jiffies;
526 
527 	adjust_total_allocated(b, false);
528 }
529 
530 /*
531  * Unlink buffer from the buffer tree and dirty or clean queue.
532  */
__unlink_buffer(struct dm_buffer * b)533 static void __unlink_buffer(struct dm_buffer *b)
534 {
535 	struct dm_bufio_client *c = b->c;
536 
537 	BUG_ON(!c->n_buffers[b->list_mode]);
538 
539 	c->n_buffers[b->list_mode]--;
540 	__remove(b->c, b);
541 	list_del(&b->lru_list);
542 
543 	adjust_total_allocated(b, true);
544 }
545 
546 /*
547  * Place the buffer to the head of dirty or clean LRU queue.
548  */
__relink_lru(struct dm_buffer * b,int dirty)549 static void __relink_lru(struct dm_buffer *b, int dirty)
550 {
551 	struct dm_bufio_client *c = b->c;
552 
553 	b->accessed = 1;
554 
555 	BUG_ON(!c->n_buffers[b->list_mode]);
556 
557 	c->n_buffers[b->list_mode]--;
558 	c->n_buffers[dirty]++;
559 	b->list_mode = dirty;
560 	list_move(&b->lru_list, &c->lru[dirty]);
561 	b->last_accessed = jiffies;
562 }
563 
564 /*----------------------------------------------------------------
565  * Submit I/O on the buffer.
566  *
567  * Bio interface is faster but it has some problems:
568  *	the vector list is limited (increasing this limit increases
569  *	memory-consumption per buffer, so it is not viable);
570  *
571  *	the memory must be direct-mapped, not vmalloced;
572  *
573  * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
574  * it is not vmalloced, try using the bio interface.
575  *
576  * If the buffer is big, if it is vmalloced or if the underlying device
577  * rejects the bio because it is too large, use dm-io layer to do the I/O.
578  * The dm-io layer splits the I/O into multiple requests, avoiding the above
579  * shortcomings.
580  *--------------------------------------------------------------*/
581 
582 /*
583  * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
584  * that the request was handled directly with bio interface.
585  */
dmio_complete(unsigned long error,void * context)586 static void dmio_complete(unsigned long error, void *context)
587 {
588 	struct dm_buffer *b = context;
589 
590 	b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
591 }
592 
use_dmio(struct dm_buffer * b,enum req_op op,sector_t sector,unsigned n_sectors,unsigned offset)593 static void use_dmio(struct dm_buffer *b, enum req_op op, sector_t sector,
594 		     unsigned n_sectors, unsigned offset)
595 {
596 	int r;
597 	struct dm_io_request io_req = {
598 		.bi_opf = op,
599 		.notify.fn = dmio_complete,
600 		.notify.context = b,
601 		.client = b->c->dm_io,
602 	};
603 	struct dm_io_region region = {
604 		.bdev = b->c->bdev,
605 		.sector = sector,
606 		.count = n_sectors,
607 	};
608 
609 	if (b->data_mode != DATA_MODE_VMALLOC) {
610 		io_req.mem.type = DM_IO_KMEM;
611 		io_req.mem.ptr.addr = (char *)b->data + offset;
612 	} else {
613 		io_req.mem.type = DM_IO_VMA;
614 		io_req.mem.ptr.vma = (char *)b->data + offset;
615 	}
616 
617 	r = dm_io(&io_req, 1, &region, NULL);
618 	if (unlikely(r))
619 		b->end_io(b, errno_to_blk_status(r));
620 }
621 
bio_complete(struct bio * bio)622 static void bio_complete(struct bio *bio)
623 {
624 	struct dm_buffer *b = bio->bi_private;
625 	blk_status_t status = bio->bi_status;
626 	bio_uninit(bio);
627 	kfree(bio);
628 	b->end_io(b, status);
629 }
630 
use_bio(struct dm_buffer * b,enum req_op op,sector_t sector,unsigned n_sectors,unsigned offset)631 static void use_bio(struct dm_buffer *b, enum req_op op, sector_t sector,
632 		    unsigned n_sectors, unsigned offset)
633 {
634 	struct bio *bio;
635 	char *ptr;
636 	unsigned vec_size, len;
637 
638 	vec_size = b->c->block_size >> PAGE_SHIFT;
639 	if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT))
640 		vec_size += 2;
641 
642 	bio = bio_kmalloc(vec_size, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN);
643 	if (!bio) {
644 dmio:
645 		use_dmio(b, op, sector, n_sectors, offset);
646 		return;
647 	}
648 	bio_init(bio, b->c->bdev, bio->bi_inline_vecs, vec_size, op);
649 	bio->bi_iter.bi_sector = sector;
650 	bio->bi_end_io = bio_complete;
651 	bio->bi_private = b;
652 
653 	ptr = (char *)b->data + offset;
654 	len = n_sectors << SECTOR_SHIFT;
655 
656 	do {
657 		unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len);
658 		if (!bio_add_page(bio, virt_to_page(ptr), this_step,
659 				  offset_in_page(ptr))) {
660 			bio_put(bio);
661 			goto dmio;
662 		}
663 
664 		len -= this_step;
665 		ptr += this_step;
666 	} while (len > 0);
667 
668 	submit_bio(bio);
669 }
670 
block_to_sector(struct dm_bufio_client * c,sector_t block)671 static inline sector_t block_to_sector(struct dm_bufio_client *c, sector_t block)
672 {
673 	sector_t sector;
674 
675 	if (likely(c->sectors_per_block_bits >= 0))
676 		sector = block << c->sectors_per_block_bits;
677 	else
678 		sector = block * (c->block_size >> SECTOR_SHIFT);
679 	sector += c->start;
680 
681 	return sector;
682 }
683 
submit_io(struct dm_buffer * b,enum req_op op,void (* end_io)(struct dm_buffer *,blk_status_t))684 static void submit_io(struct dm_buffer *b, enum req_op op,
685 		      void (*end_io)(struct dm_buffer *, blk_status_t))
686 {
687 	unsigned n_sectors;
688 	sector_t sector;
689 	unsigned offset, end;
690 
691 	b->end_io = end_io;
692 
693 	sector = block_to_sector(b->c, b->block);
694 
695 	if (op != REQ_OP_WRITE) {
696 		n_sectors = b->c->block_size >> SECTOR_SHIFT;
697 		offset = 0;
698 	} else {
699 		if (b->c->write_callback)
700 			b->c->write_callback(b);
701 		offset = b->write_start;
702 		end = b->write_end;
703 		offset &= -DM_BUFIO_WRITE_ALIGN;
704 		end += DM_BUFIO_WRITE_ALIGN - 1;
705 		end &= -DM_BUFIO_WRITE_ALIGN;
706 		if (unlikely(end > b->c->block_size))
707 			end = b->c->block_size;
708 
709 		sector += offset >> SECTOR_SHIFT;
710 		n_sectors = (end - offset) >> SECTOR_SHIFT;
711 	}
712 
713 	if (b->data_mode != DATA_MODE_VMALLOC)
714 		use_bio(b, op, sector, n_sectors, offset);
715 	else
716 		use_dmio(b, op, sector, n_sectors, offset);
717 }
718 
719 /*----------------------------------------------------------------
720  * Writing dirty buffers
721  *--------------------------------------------------------------*/
722 
723 /*
724  * The endio routine for write.
725  *
726  * Set the error, clear B_WRITING bit and wake anyone who was waiting on
727  * it.
728  */
write_endio(struct dm_buffer * b,blk_status_t status)729 static void write_endio(struct dm_buffer *b, blk_status_t status)
730 {
731 	b->write_error = status;
732 	if (unlikely(status)) {
733 		struct dm_bufio_client *c = b->c;
734 
735 		(void)cmpxchg(&c->async_write_error, 0,
736 				blk_status_to_errno(status));
737 	}
738 
739 	BUG_ON(!test_bit(B_WRITING, &b->state));
740 
741 	smp_mb__before_atomic();
742 	clear_bit(B_WRITING, &b->state);
743 	smp_mb__after_atomic();
744 
745 	wake_up_bit(&b->state, B_WRITING);
746 }
747 
748 /*
749  * Initiate a write on a dirty buffer, but don't wait for it.
750  *
751  * - If the buffer is not dirty, exit.
752  * - If there some previous write going on, wait for it to finish (we can't
753  *   have two writes on the same buffer simultaneously).
754  * - Submit our write and don't wait on it. We set B_WRITING indicating
755  *   that there is a write in progress.
756  */
__write_dirty_buffer(struct dm_buffer * b,struct list_head * write_list)757 static void __write_dirty_buffer(struct dm_buffer *b,
758 				 struct list_head *write_list)
759 {
760 	if (!test_bit(B_DIRTY, &b->state))
761 		return;
762 
763 	clear_bit(B_DIRTY, &b->state);
764 	wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
765 
766 	b->write_start = b->dirty_start;
767 	b->write_end = b->dirty_end;
768 
769 	if (!write_list)
770 		submit_io(b, REQ_OP_WRITE, write_endio);
771 	else
772 		list_add_tail(&b->write_list, write_list);
773 }
774 
__flush_write_list(struct list_head * write_list)775 static void __flush_write_list(struct list_head *write_list)
776 {
777 	struct blk_plug plug;
778 	blk_start_plug(&plug);
779 	while (!list_empty(write_list)) {
780 		struct dm_buffer *b =
781 			list_entry(write_list->next, struct dm_buffer, write_list);
782 		list_del(&b->write_list);
783 		submit_io(b, REQ_OP_WRITE, write_endio);
784 		cond_resched();
785 	}
786 	blk_finish_plug(&plug);
787 }
788 
789 /*
790  * Wait until any activity on the buffer finishes.  Possibly write the
791  * buffer if it is dirty.  When this function finishes, there is no I/O
792  * running on the buffer and the buffer is not dirty.
793  */
__make_buffer_clean(struct dm_buffer * b)794 static void __make_buffer_clean(struct dm_buffer *b)
795 {
796 	BUG_ON(b->hold_count);
797 
798 	/* smp_load_acquire() pairs with read_endio()'s smp_mb__before_atomic() */
799 	if (!smp_load_acquire(&b->state))	/* fast case */
800 		return;
801 
802 	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
803 	__write_dirty_buffer(b, NULL);
804 	wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
805 }
806 
807 /*
808  * Find some buffer that is not held by anybody, clean it, unlink it and
809  * return it.
810  */
__get_unclaimed_buffer(struct dm_bufio_client * c)811 static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
812 {
813 	struct dm_buffer *b;
814 
815 	list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
816 		BUG_ON(test_bit(B_WRITING, &b->state));
817 		BUG_ON(test_bit(B_DIRTY, &b->state));
818 
819 		if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep &&
820 		    unlikely(test_bit_acquire(B_READING, &b->state)))
821 			continue;
822 
823 		if (!b->hold_count) {
824 			__make_buffer_clean(b);
825 			__unlink_buffer(b);
826 			return b;
827 		}
828 		cond_resched();
829 	}
830 
831 	if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
832 		return NULL;
833 
834 	list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
835 		BUG_ON(test_bit(B_READING, &b->state));
836 
837 		if (!b->hold_count) {
838 			__make_buffer_clean(b);
839 			__unlink_buffer(b);
840 			return b;
841 		}
842 		cond_resched();
843 	}
844 
845 	return NULL;
846 }
847 
848 /*
849  * Wait until some other threads free some buffer or release hold count on
850  * some buffer.
851  *
852  * This function is entered with c->lock held, drops it and regains it
853  * before exiting.
854  */
__wait_for_free_buffer(struct dm_bufio_client * c)855 static void __wait_for_free_buffer(struct dm_bufio_client *c)
856 {
857 	DECLARE_WAITQUEUE(wait, current);
858 
859 	add_wait_queue(&c->free_buffer_wait, &wait);
860 	set_current_state(TASK_UNINTERRUPTIBLE);
861 	dm_bufio_unlock(c);
862 
863 	io_schedule();
864 
865 	remove_wait_queue(&c->free_buffer_wait, &wait);
866 
867 	dm_bufio_lock(c);
868 }
869 
870 enum new_flag {
871 	NF_FRESH = 0,
872 	NF_READ = 1,
873 	NF_GET = 2,
874 	NF_PREFETCH = 3
875 };
876 
877 /*
878  * Allocate a new buffer. If the allocation is not possible, wait until
879  * some other thread frees a buffer.
880  *
881  * May drop the lock and regain it.
882  */
__alloc_buffer_wait_no_callback(struct dm_bufio_client * c,enum new_flag nf)883 static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
884 {
885 	struct dm_buffer *b;
886 	bool tried_noio_alloc = false;
887 
888 	/*
889 	 * dm-bufio is resistant to allocation failures (it just keeps
890 	 * one buffer reserved in cases all the allocations fail).
891 	 * So set flags to not try too hard:
892 	 *	GFP_NOWAIT: don't wait; if we need to sleep we'll release our
893 	 *		    mutex and wait ourselves.
894 	 *	__GFP_NORETRY: don't retry and rather return failure
895 	 *	__GFP_NOMEMALLOC: don't use emergency reserves
896 	 *	__GFP_NOWARN: don't print a warning in case of failure
897 	 *
898 	 * For debugging, if we set the cache size to 1, no new buffers will
899 	 * be allocated.
900 	 */
901 	while (1) {
902 		if (dm_bufio_cache_size_latch != 1) {
903 			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
904 			if (b)
905 				return b;
906 		}
907 
908 		if (nf == NF_PREFETCH)
909 			return NULL;
910 
911 		if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
912 			dm_bufio_unlock(c);
913 			b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
914 			dm_bufio_lock(c);
915 			if (b)
916 				return b;
917 			tried_noio_alloc = true;
918 		}
919 
920 		if (!list_empty(&c->reserved_buffers)) {
921 			b = list_entry(c->reserved_buffers.next,
922 				       struct dm_buffer, lru_list);
923 			list_del(&b->lru_list);
924 			c->need_reserved_buffers++;
925 
926 			return b;
927 		}
928 
929 		b = __get_unclaimed_buffer(c);
930 		if (b)
931 			return b;
932 
933 		__wait_for_free_buffer(c);
934 	}
935 }
936 
__alloc_buffer_wait(struct dm_bufio_client * c,enum new_flag nf)937 static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
938 {
939 	struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
940 
941 	if (!b)
942 		return NULL;
943 
944 	if (c->alloc_callback)
945 		c->alloc_callback(b);
946 
947 	return b;
948 }
949 
950 /*
951  * Free a buffer and wake other threads waiting for free buffers.
952  */
__free_buffer_wake(struct dm_buffer * b)953 static void __free_buffer_wake(struct dm_buffer *b)
954 {
955 	struct dm_bufio_client *c = b->c;
956 
957 	if (!c->need_reserved_buffers)
958 		free_buffer(b);
959 	else {
960 		list_add(&b->lru_list, &c->reserved_buffers);
961 		c->need_reserved_buffers--;
962 	}
963 
964 	wake_up(&c->free_buffer_wait);
965 }
966 
__write_dirty_buffers_async(struct dm_bufio_client * c,int no_wait,struct list_head * write_list)967 static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
968 					struct list_head *write_list)
969 {
970 	struct dm_buffer *b, *tmp;
971 
972 	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
973 		BUG_ON(test_bit(B_READING, &b->state));
974 
975 		if (!test_bit(B_DIRTY, &b->state) &&
976 		    !test_bit(B_WRITING, &b->state)) {
977 			__relink_lru(b, LIST_CLEAN);
978 			continue;
979 		}
980 
981 		if (no_wait && test_bit(B_WRITING, &b->state))
982 			return;
983 
984 		__write_dirty_buffer(b, write_list);
985 		cond_resched();
986 	}
987 }
988 
989 /*
990  * Check if we're over watermark.
991  * If we are over threshold_buffers, start freeing buffers.
992  * If we're over "limit_buffers", block until we get under the limit.
993  */
__check_watermark(struct dm_bufio_client * c,struct list_head * write_list)994 static void __check_watermark(struct dm_bufio_client *c,
995 			      struct list_head *write_list)
996 {
997 	if (c->n_buffers[LIST_DIRTY] > c->n_buffers[LIST_CLEAN] * DM_BUFIO_WRITEBACK_RATIO)
998 		__write_dirty_buffers_async(c, 1, write_list);
999 }
1000 
1001 /*----------------------------------------------------------------
1002  * Getting a buffer
1003  *--------------------------------------------------------------*/
1004 
__bufio_new(struct dm_bufio_client * c,sector_t block,enum new_flag nf,int * need_submit,struct list_head * write_list)1005 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
1006 				     enum new_flag nf, int *need_submit,
1007 				     struct list_head *write_list)
1008 {
1009 	struct dm_buffer *b, *new_b = NULL;
1010 
1011 	*need_submit = 0;
1012 
1013 	b = __find(c, block);
1014 	if (b)
1015 		goto found_buffer;
1016 
1017 	if (nf == NF_GET)
1018 		return NULL;
1019 
1020 	new_b = __alloc_buffer_wait(c, nf);
1021 	if (!new_b)
1022 		return NULL;
1023 
1024 	/*
1025 	 * We've had a period where the mutex was unlocked, so need to
1026 	 * recheck the buffer tree.
1027 	 */
1028 	b = __find(c, block);
1029 	if (b) {
1030 		__free_buffer_wake(new_b);
1031 		goto found_buffer;
1032 	}
1033 
1034 	__check_watermark(c, write_list);
1035 
1036 	b = new_b;
1037 	b->hold_count = 1;
1038 	b->read_error = 0;
1039 	b->write_error = 0;
1040 	__link_buffer(b, block, LIST_CLEAN);
1041 
1042 	if (nf == NF_FRESH) {
1043 		b->state = 0;
1044 		return b;
1045 	}
1046 
1047 	b->state = 1 << B_READING;
1048 	*need_submit = 1;
1049 
1050 	return b;
1051 
1052 found_buffer:
1053 	if (nf == NF_PREFETCH)
1054 		return NULL;
1055 	/*
1056 	 * Note: it is essential that we don't wait for the buffer to be
1057 	 * read if dm_bufio_get function is used. Both dm_bufio_get and
1058 	 * dm_bufio_prefetch can be used in the driver request routine.
1059 	 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1060 	 * the same buffer, it would deadlock if we waited.
1061 	 */
1062 	if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state)))
1063 		return NULL;
1064 
1065 	b->hold_count++;
1066 	__relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1067 		     test_bit(B_WRITING, &b->state));
1068 	return b;
1069 }
1070 
1071 /*
1072  * The endio routine for reading: set the error, clear the bit and wake up
1073  * anyone waiting on the buffer.
1074  */
read_endio(struct dm_buffer * b,blk_status_t status)1075 static void read_endio(struct dm_buffer *b, blk_status_t status)
1076 {
1077 	b->read_error = status;
1078 
1079 	BUG_ON(!test_bit(B_READING, &b->state));
1080 
1081 	smp_mb__before_atomic();
1082 	clear_bit(B_READING, &b->state);
1083 	smp_mb__after_atomic();
1084 
1085 	wake_up_bit(&b->state, B_READING);
1086 }
1087 
1088 /*
1089  * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
1090  * functions is similar except that dm_bufio_new doesn't read the
1091  * buffer from the disk (assuming that the caller overwrites all the data
1092  * and uses dm_bufio_mark_buffer_dirty to write new data back).
1093  */
new_read(struct dm_bufio_client * c,sector_t block,enum new_flag nf,struct dm_buffer ** bp)1094 static void *new_read(struct dm_bufio_client *c, sector_t block,
1095 		      enum new_flag nf, struct dm_buffer **bp)
1096 {
1097 	int need_submit;
1098 	struct dm_buffer *b;
1099 
1100 	LIST_HEAD(write_list);
1101 
1102 	dm_bufio_lock(c);
1103 	b = __bufio_new(c, block, nf, &need_submit, &write_list);
1104 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1105 	if (b && b->hold_count == 1)
1106 		buffer_record_stack(b);
1107 #endif
1108 	dm_bufio_unlock(c);
1109 
1110 	__flush_write_list(&write_list);
1111 
1112 	if (!b)
1113 		return NULL;
1114 
1115 	if (need_submit)
1116 		submit_io(b, REQ_OP_READ, read_endio);
1117 
1118 	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1119 
1120 	if (b->read_error) {
1121 		int error = blk_status_to_errno(b->read_error);
1122 
1123 		dm_bufio_release(b);
1124 
1125 		return ERR_PTR(error);
1126 	}
1127 
1128 	*bp = b;
1129 
1130 	return b->data;
1131 }
1132 
dm_bufio_get(struct dm_bufio_client * c,sector_t block,struct dm_buffer ** bp)1133 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1134 		   struct dm_buffer **bp)
1135 {
1136 	return new_read(c, block, NF_GET, bp);
1137 }
1138 EXPORT_SYMBOL_GPL(dm_bufio_get);
1139 
dm_bufio_read(struct dm_bufio_client * c,sector_t block,struct dm_buffer ** bp)1140 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1141 		    struct dm_buffer **bp)
1142 {
1143 	BUG_ON(dm_bufio_in_request());
1144 
1145 	return new_read(c, block, NF_READ, bp);
1146 }
1147 EXPORT_SYMBOL_GPL(dm_bufio_read);
1148 
dm_bufio_new(struct dm_bufio_client * c,sector_t block,struct dm_buffer ** bp)1149 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1150 		   struct dm_buffer **bp)
1151 {
1152 	BUG_ON(dm_bufio_in_request());
1153 
1154 	return new_read(c, block, NF_FRESH, bp);
1155 }
1156 EXPORT_SYMBOL_GPL(dm_bufio_new);
1157 
dm_bufio_prefetch(struct dm_bufio_client * c,sector_t block,unsigned n_blocks)1158 void dm_bufio_prefetch(struct dm_bufio_client *c,
1159 		       sector_t block, unsigned n_blocks)
1160 {
1161 	struct blk_plug plug;
1162 
1163 	LIST_HEAD(write_list);
1164 
1165 	BUG_ON(dm_bufio_in_request());
1166 
1167 	blk_start_plug(&plug);
1168 	dm_bufio_lock(c);
1169 
1170 	for (; n_blocks--; block++) {
1171 		int need_submit;
1172 		struct dm_buffer *b;
1173 		b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1174 				&write_list);
1175 		if (unlikely(!list_empty(&write_list))) {
1176 			dm_bufio_unlock(c);
1177 			blk_finish_plug(&plug);
1178 			__flush_write_list(&write_list);
1179 			blk_start_plug(&plug);
1180 			dm_bufio_lock(c);
1181 		}
1182 		if (unlikely(b != NULL)) {
1183 			dm_bufio_unlock(c);
1184 
1185 			if (need_submit)
1186 				submit_io(b, REQ_OP_READ, read_endio);
1187 			dm_bufio_release(b);
1188 
1189 			cond_resched();
1190 
1191 			if (!n_blocks)
1192 				goto flush_plug;
1193 			dm_bufio_lock(c);
1194 		}
1195 	}
1196 
1197 	dm_bufio_unlock(c);
1198 
1199 flush_plug:
1200 	blk_finish_plug(&plug);
1201 }
1202 EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1203 
dm_bufio_release(struct dm_buffer * b)1204 void dm_bufio_release(struct dm_buffer *b)
1205 {
1206 	struct dm_bufio_client *c = b->c;
1207 
1208 	dm_bufio_lock(c);
1209 
1210 	BUG_ON(!b->hold_count);
1211 
1212 	b->hold_count--;
1213 	if (!b->hold_count) {
1214 		wake_up(&c->free_buffer_wait);
1215 
1216 		/*
1217 		 * If there were errors on the buffer, and the buffer is not
1218 		 * to be written, free the buffer. There is no point in caching
1219 		 * invalid buffer.
1220 		 */
1221 		if ((b->read_error || b->write_error) &&
1222 		    !test_bit_acquire(B_READING, &b->state) &&
1223 		    !test_bit(B_WRITING, &b->state) &&
1224 		    !test_bit(B_DIRTY, &b->state)) {
1225 			__unlink_buffer(b);
1226 			__free_buffer_wake(b);
1227 		}
1228 	}
1229 
1230 	dm_bufio_unlock(c);
1231 }
1232 EXPORT_SYMBOL_GPL(dm_bufio_release);
1233 
dm_bufio_mark_partial_buffer_dirty(struct dm_buffer * b,unsigned start,unsigned end)1234 void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
1235 					unsigned start, unsigned end)
1236 {
1237 	struct dm_bufio_client *c = b->c;
1238 
1239 	BUG_ON(start >= end);
1240 	BUG_ON(end > b->c->block_size);
1241 
1242 	dm_bufio_lock(c);
1243 
1244 	BUG_ON(test_bit(B_READING, &b->state));
1245 
1246 	if (!test_and_set_bit(B_DIRTY, &b->state)) {
1247 		b->dirty_start = start;
1248 		b->dirty_end = end;
1249 		__relink_lru(b, LIST_DIRTY);
1250 	} else {
1251 		if (start < b->dirty_start)
1252 			b->dirty_start = start;
1253 		if (end > b->dirty_end)
1254 			b->dirty_end = end;
1255 	}
1256 
1257 	dm_bufio_unlock(c);
1258 }
1259 EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
1260 
dm_bufio_mark_buffer_dirty(struct dm_buffer * b)1261 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1262 {
1263 	dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
1264 }
1265 EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1266 
dm_bufio_write_dirty_buffers_async(struct dm_bufio_client * c)1267 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1268 {
1269 	LIST_HEAD(write_list);
1270 
1271 	BUG_ON(dm_bufio_in_request());
1272 
1273 	dm_bufio_lock(c);
1274 	__write_dirty_buffers_async(c, 0, &write_list);
1275 	dm_bufio_unlock(c);
1276 	__flush_write_list(&write_list);
1277 }
1278 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1279 
1280 /*
1281  * For performance, it is essential that the buffers are written asynchronously
1282  * and simultaneously (so that the block layer can merge the writes) and then
1283  * waited upon.
1284  *
1285  * Finally, we flush hardware disk cache.
1286  */
dm_bufio_write_dirty_buffers(struct dm_bufio_client * c)1287 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1288 {
1289 	int a, f;
1290 	unsigned long buffers_processed = 0;
1291 	struct dm_buffer *b, *tmp;
1292 
1293 	LIST_HEAD(write_list);
1294 
1295 	dm_bufio_lock(c);
1296 	__write_dirty_buffers_async(c, 0, &write_list);
1297 	dm_bufio_unlock(c);
1298 	__flush_write_list(&write_list);
1299 	dm_bufio_lock(c);
1300 
1301 again:
1302 	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1303 		int dropped_lock = 0;
1304 
1305 		if (buffers_processed < c->n_buffers[LIST_DIRTY])
1306 			buffers_processed++;
1307 
1308 		BUG_ON(test_bit(B_READING, &b->state));
1309 
1310 		if (test_bit(B_WRITING, &b->state)) {
1311 			if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1312 				dropped_lock = 1;
1313 				b->hold_count++;
1314 				dm_bufio_unlock(c);
1315 				wait_on_bit_io(&b->state, B_WRITING,
1316 					       TASK_UNINTERRUPTIBLE);
1317 				dm_bufio_lock(c);
1318 				b->hold_count--;
1319 			} else
1320 				wait_on_bit_io(&b->state, B_WRITING,
1321 					       TASK_UNINTERRUPTIBLE);
1322 		}
1323 
1324 		if (!test_bit(B_DIRTY, &b->state) &&
1325 		    !test_bit(B_WRITING, &b->state))
1326 			__relink_lru(b, LIST_CLEAN);
1327 
1328 		cond_resched();
1329 
1330 		/*
1331 		 * If we dropped the lock, the list is no longer consistent,
1332 		 * so we must restart the search.
1333 		 *
1334 		 * In the most common case, the buffer just processed is
1335 		 * relinked to the clean list, so we won't loop scanning the
1336 		 * same buffer again and again.
1337 		 *
1338 		 * This may livelock if there is another thread simultaneously
1339 		 * dirtying buffers, so we count the number of buffers walked
1340 		 * and if it exceeds the total number of buffers, it means that
1341 		 * someone is doing some writes simultaneously with us.  In
1342 		 * this case, stop, dropping the lock.
1343 		 */
1344 		if (dropped_lock)
1345 			goto again;
1346 	}
1347 	wake_up(&c->free_buffer_wait);
1348 	dm_bufio_unlock(c);
1349 
1350 	a = xchg(&c->async_write_error, 0);
1351 	f = dm_bufio_issue_flush(c);
1352 	if (a)
1353 		return a;
1354 
1355 	return f;
1356 }
1357 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1358 
1359 /*
1360  * Use dm-io to send an empty barrier to flush the device.
1361  */
dm_bufio_issue_flush(struct dm_bufio_client * c)1362 int dm_bufio_issue_flush(struct dm_bufio_client *c)
1363 {
1364 	struct dm_io_request io_req = {
1365 		.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
1366 		.mem.type = DM_IO_KMEM,
1367 		.mem.ptr.addr = NULL,
1368 		.client = c->dm_io,
1369 	};
1370 	struct dm_io_region io_reg = {
1371 		.bdev = c->bdev,
1372 		.sector = 0,
1373 		.count = 0,
1374 	};
1375 
1376 	BUG_ON(dm_bufio_in_request());
1377 
1378 	return dm_io(&io_req, 1, &io_reg, NULL);
1379 }
1380 EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1381 
1382 /*
1383  * Use dm-io to send a discard request to flush the device.
1384  */
dm_bufio_issue_discard(struct dm_bufio_client * c,sector_t block,sector_t count)1385 int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t count)
1386 {
1387 	struct dm_io_request io_req = {
1388 		.bi_opf = REQ_OP_DISCARD | REQ_SYNC,
1389 		.mem.type = DM_IO_KMEM,
1390 		.mem.ptr.addr = NULL,
1391 		.client = c->dm_io,
1392 	};
1393 	struct dm_io_region io_reg = {
1394 		.bdev = c->bdev,
1395 		.sector = block_to_sector(c, block),
1396 		.count = block_to_sector(c, count),
1397 	};
1398 
1399 	BUG_ON(dm_bufio_in_request());
1400 
1401 	return dm_io(&io_req, 1, &io_reg, NULL);
1402 }
1403 EXPORT_SYMBOL_GPL(dm_bufio_issue_discard);
1404 
1405 /*
1406  * We first delete any other buffer that may be at that new location.
1407  *
1408  * Then, we write the buffer to the original location if it was dirty.
1409  *
1410  * Then, if we are the only one who is holding the buffer, relink the buffer
1411  * in the buffer tree for the new location.
1412  *
1413  * If there was someone else holding the buffer, we write it to the new
1414  * location but not relink it, because that other user needs to have the buffer
1415  * at the same place.
1416  */
dm_bufio_release_move(struct dm_buffer * b,sector_t new_block)1417 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1418 {
1419 	struct dm_bufio_client *c = b->c;
1420 	struct dm_buffer *new;
1421 
1422 	BUG_ON(dm_bufio_in_request());
1423 
1424 	dm_bufio_lock(c);
1425 
1426 retry:
1427 	new = __find(c, new_block);
1428 	if (new) {
1429 		if (new->hold_count) {
1430 			__wait_for_free_buffer(c);
1431 			goto retry;
1432 		}
1433 
1434 		/*
1435 		 * FIXME: Is there any point waiting for a write that's going
1436 		 * to be overwritten in a bit?
1437 		 */
1438 		__make_buffer_clean(new);
1439 		__unlink_buffer(new);
1440 		__free_buffer_wake(new);
1441 	}
1442 
1443 	BUG_ON(!b->hold_count);
1444 	BUG_ON(test_bit(B_READING, &b->state));
1445 
1446 	__write_dirty_buffer(b, NULL);
1447 	if (b->hold_count == 1) {
1448 		wait_on_bit_io(&b->state, B_WRITING,
1449 			       TASK_UNINTERRUPTIBLE);
1450 		set_bit(B_DIRTY, &b->state);
1451 		b->dirty_start = 0;
1452 		b->dirty_end = c->block_size;
1453 		__unlink_buffer(b);
1454 		__link_buffer(b, new_block, LIST_DIRTY);
1455 	} else {
1456 		sector_t old_block;
1457 		wait_on_bit_lock_io(&b->state, B_WRITING,
1458 				    TASK_UNINTERRUPTIBLE);
1459 		/*
1460 		 * Relink buffer to "new_block" so that write_callback
1461 		 * sees "new_block" as a block number.
1462 		 * After the write, link the buffer back to old_block.
1463 		 * All this must be done in bufio lock, so that block number
1464 		 * change isn't visible to other threads.
1465 		 */
1466 		old_block = b->block;
1467 		__unlink_buffer(b);
1468 		__link_buffer(b, new_block, b->list_mode);
1469 		submit_io(b, REQ_OP_WRITE, write_endio);
1470 		wait_on_bit_io(&b->state, B_WRITING,
1471 			       TASK_UNINTERRUPTIBLE);
1472 		__unlink_buffer(b);
1473 		__link_buffer(b, old_block, b->list_mode);
1474 	}
1475 
1476 	dm_bufio_unlock(c);
1477 	dm_bufio_release(b);
1478 }
1479 EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1480 
forget_buffer_locked(struct dm_buffer * b)1481 static void forget_buffer_locked(struct dm_buffer *b)
1482 {
1483 	if (likely(!b->hold_count) && likely(!smp_load_acquire(&b->state))) {
1484 		__unlink_buffer(b);
1485 		__free_buffer_wake(b);
1486 	}
1487 }
1488 
1489 /*
1490  * Free the given buffer.
1491  *
1492  * This is just a hint, if the buffer is in use or dirty, this function
1493  * does nothing.
1494  */
dm_bufio_forget(struct dm_bufio_client * c,sector_t block)1495 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1496 {
1497 	struct dm_buffer *b;
1498 
1499 	dm_bufio_lock(c);
1500 
1501 	b = __find(c, block);
1502 	if (b)
1503 		forget_buffer_locked(b);
1504 
1505 	dm_bufio_unlock(c);
1506 }
1507 EXPORT_SYMBOL_GPL(dm_bufio_forget);
1508 
dm_bufio_forget_buffers(struct dm_bufio_client * c,sector_t block,sector_t n_blocks)1509 void dm_bufio_forget_buffers(struct dm_bufio_client *c, sector_t block, sector_t n_blocks)
1510 {
1511 	struct dm_buffer *b;
1512 	sector_t end_block = block + n_blocks;
1513 
1514 	while (block < end_block) {
1515 		dm_bufio_lock(c);
1516 
1517 		b = __find_next(c, block);
1518 		if (b) {
1519 			block = b->block + 1;
1520 			forget_buffer_locked(b);
1521 		}
1522 
1523 		dm_bufio_unlock(c);
1524 
1525 		if (!b)
1526 			break;
1527 	}
1528 
1529 }
1530 EXPORT_SYMBOL_GPL(dm_bufio_forget_buffers);
1531 
dm_bufio_set_minimum_buffers(struct dm_bufio_client * c,unsigned n)1532 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1533 {
1534 	c->minimum_buffers = n;
1535 }
1536 EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
1537 
dm_bufio_get_block_size(struct dm_bufio_client * c)1538 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1539 {
1540 	return c->block_size;
1541 }
1542 EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1543 
dm_bufio_get_device_size(struct dm_bufio_client * c)1544 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1545 {
1546 	sector_t s = bdev_nr_sectors(c->bdev);
1547 	if (s >= c->start)
1548 		s -= c->start;
1549 	else
1550 		s = 0;
1551 	if (likely(c->sectors_per_block_bits >= 0))
1552 		s >>= c->sectors_per_block_bits;
1553 	else
1554 		sector_div(s, c->block_size >> SECTOR_SHIFT);
1555 	return s;
1556 }
1557 EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1558 
dm_bufio_get_dm_io_client(struct dm_bufio_client * c)1559 struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c)
1560 {
1561 	return c->dm_io;
1562 }
1563 EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client);
1564 
dm_bufio_get_block_number(struct dm_buffer * b)1565 sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1566 {
1567 	return b->block;
1568 }
1569 EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1570 
dm_bufio_get_block_data(struct dm_buffer * b)1571 void *dm_bufio_get_block_data(struct dm_buffer *b)
1572 {
1573 	return b->data;
1574 }
1575 EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1576 
dm_bufio_get_aux_data(struct dm_buffer * b)1577 void *dm_bufio_get_aux_data(struct dm_buffer *b)
1578 {
1579 	return b + 1;
1580 }
1581 EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1582 
dm_bufio_get_client(struct dm_buffer * b)1583 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1584 {
1585 	return b->c;
1586 }
1587 EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1588 
drop_buffers(struct dm_bufio_client * c)1589 static void drop_buffers(struct dm_bufio_client *c)
1590 {
1591 	struct dm_buffer *b;
1592 	int i;
1593 	bool warned = false;
1594 
1595 	BUG_ON(dm_bufio_in_request());
1596 
1597 	/*
1598 	 * An optimization so that the buffers are not written one-by-one.
1599 	 */
1600 	dm_bufio_write_dirty_buffers_async(c);
1601 
1602 	dm_bufio_lock(c);
1603 
1604 	while ((b = __get_unclaimed_buffer(c)))
1605 		__free_buffer_wake(b);
1606 
1607 	for (i = 0; i < LIST_SIZE; i++)
1608 		list_for_each_entry(b, &c->lru[i], lru_list) {
1609 			WARN_ON(!warned);
1610 			warned = true;
1611 			DMERR("leaked buffer %llx, hold count %u, list %d",
1612 			      (unsigned long long)b->block, b->hold_count, i);
1613 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1614 			stack_trace_print(b->stack_entries, b->stack_len, 1);
1615 			/* mark unclaimed to avoid BUG_ON below */
1616 			b->hold_count = 0;
1617 #endif
1618 		}
1619 
1620 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1621 	while ((b = __get_unclaimed_buffer(c)))
1622 		__free_buffer_wake(b);
1623 #endif
1624 
1625 	for (i = 0; i < LIST_SIZE; i++)
1626 		BUG_ON(!list_empty(&c->lru[i]));
1627 
1628 	dm_bufio_unlock(c);
1629 }
1630 
1631 /*
1632  * We may not be able to evict this buffer if IO pending or the client
1633  * is still using it.  Caller is expected to know buffer is too old.
1634  *
1635  * And if GFP_NOFS is used, we must not do any I/O because we hold
1636  * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1637  * rerouted to different bufio client.
1638  */
__try_evict_buffer(struct dm_buffer * b,gfp_t gfp)1639 static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1640 {
1641 	if (!(gfp & __GFP_FS) ||
1642 	    (static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
1643 		if (test_bit_acquire(B_READING, &b->state) ||
1644 		    test_bit(B_WRITING, &b->state) ||
1645 		    test_bit(B_DIRTY, &b->state))
1646 			return false;
1647 	}
1648 
1649 	if (b->hold_count)
1650 		return false;
1651 
1652 	__make_buffer_clean(b);
1653 	__unlink_buffer(b);
1654 	__free_buffer_wake(b);
1655 
1656 	return true;
1657 }
1658 
get_retain_buffers(struct dm_bufio_client * c)1659 static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1660 {
1661 	unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
1662 	if (likely(c->sectors_per_block_bits >= 0))
1663 		retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
1664 	else
1665 		retain_bytes /= c->block_size;
1666 	return retain_bytes;
1667 }
1668 
__scan(struct dm_bufio_client * c)1669 static void __scan(struct dm_bufio_client *c)
1670 {
1671 	int l;
1672 	struct dm_buffer *b, *tmp;
1673 	unsigned long freed = 0;
1674 	unsigned long count = c->n_buffers[LIST_CLEAN] +
1675 			      c->n_buffers[LIST_DIRTY];
1676 	unsigned long retain_target = get_retain_buffers(c);
1677 
1678 	for (l = 0; l < LIST_SIZE; l++) {
1679 		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1680 			if (count - freed <= retain_target)
1681 				atomic_long_set(&c->need_shrink, 0);
1682 			if (!atomic_long_read(&c->need_shrink))
1683 				return;
1684 			if (__try_evict_buffer(b, GFP_KERNEL)) {
1685 				atomic_long_dec(&c->need_shrink);
1686 				freed++;
1687 			}
1688 			cond_resched();
1689 		}
1690 	}
1691 }
1692 
shrink_work(struct work_struct * w)1693 static void shrink_work(struct work_struct *w)
1694 {
1695 	struct dm_bufio_client *c = container_of(w, struct dm_bufio_client, shrink_work);
1696 
1697 	dm_bufio_lock(c);
1698 	__scan(c);
1699 	dm_bufio_unlock(c);
1700 }
1701 
dm_bufio_shrink_scan(struct shrinker * shrink,struct shrink_control * sc)1702 static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1703 {
1704 	struct dm_bufio_client *c;
1705 
1706 	c = container_of(shrink, struct dm_bufio_client, shrinker);
1707 	atomic_long_add(sc->nr_to_scan, &c->need_shrink);
1708 	queue_work(dm_bufio_wq, &c->shrink_work);
1709 
1710 	return sc->nr_to_scan;
1711 }
1712 
dm_bufio_shrink_count(struct shrinker * shrink,struct shrink_control * sc)1713 static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1714 {
1715 	struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1716 	unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) +
1717 			      READ_ONCE(c->n_buffers[LIST_DIRTY]);
1718 	unsigned long retain_target = get_retain_buffers(c);
1719 	unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
1720 
1721 	if (unlikely(count < retain_target))
1722 		count = 0;
1723 	else
1724 		count -= retain_target;
1725 
1726 	if (unlikely(count < queued_for_cleanup))
1727 		count = 0;
1728 	else
1729 		count -= queued_for_cleanup;
1730 
1731 	return count;
1732 }
1733 
1734 /*
1735  * Create the buffering interface
1736  */
dm_bufio_client_create(struct block_device * bdev,unsigned block_size,unsigned reserved_buffers,unsigned aux_size,void (* alloc_callback)(struct dm_buffer *),void (* write_callback)(struct dm_buffer *),unsigned int flags)1737 struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1738 					       unsigned reserved_buffers, unsigned aux_size,
1739 					       void (*alloc_callback)(struct dm_buffer *),
1740 					       void (*write_callback)(struct dm_buffer *),
1741 					       unsigned int flags)
1742 {
1743 	int r;
1744 	struct dm_bufio_client *c;
1745 	unsigned i;
1746 	char slab_name[27];
1747 
1748 	if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
1749 		DMERR("%s: block size not specified or is not multiple of 512b", __func__);
1750 		r = -EINVAL;
1751 		goto bad_client;
1752 	}
1753 
1754 	c = kzalloc(sizeof(*c), GFP_KERNEL);
1755 	if (!c) {
1756 		r = -ENOMEM;
1757 		goto bad_client;
1758 	}
1759 	c->buffer_tree = RB_ROOT;
1760 
1761 	c->bdev = bdev;
1762 	c->block_size = block_size;
1763 	if (is_power_of_2(block_size))
1764 		c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1765 	else
1766 		c->sectors_per_block_bits = -1;
1767 
1768 	c->alloc_callback = alloc_callback;
1769 	c->write_callback = write_callback;
1770 
1771 	if (flags & DM_BUFIO_CLIENT_NO_SLEEP) {
1772 		c->no_sleep = true;
1773 		static_branch_inc(&no_sleep_enabled);
1774 	}
1775 
1776 	for (i = 0; i < LIST_SIZE; i++) {
1777 		INIT_LIST_HEAD(&c->lru[i]);
1778 		c->n_buffers[i] = 0;
1779 	}
1780 
1781 	mutex_init(&c->lock);
1782 	spin_lock_init(&c->spinlock);
1783 	INIT_LIST_HEAD(&c->reserved_buffers);
1784 	c->need_reserved_buffers = reserved_buffers;
1785 
1786 	dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
1787 
1788 	init_waitqueue_head(&c->free_buffer_wait);
1789 	c->async_write_error = 0;
1790 
1791 	c->dm_io = dm_io_client_create();
1792 	if (IS_ERR(c->dm_io)) {
1793 		r = PTR_ERR(c->dm_io);
1794 		goto bad_dm_io;
1795 	}
1796 
1797 	if (block_size <= KMALLOC_MAX_SIZE &&
1798 	    (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
1799 		unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE);
1800 		snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size);
1801 		c->slab_cache = kmem_cache_create(slab_name, block_size, align,
1802 						  SLAB_RECLAIM_ACCOUNT, NULL);
1803 		if (!c->slab_cache) {
1804 			r = -ENOMEM;
1805 			goto bad;
1806 		}
1807 	}
1808 	if (aux_size)
1809 		snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size);
1810 	else
1811 		snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer");
1812 	c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
1813 					   0, SLAB_RECLAIM_ACCOUNT, NULL);
1814 	if (!c->slab_buffer) {
1815 		r = -ENOMEM;
1816 		goto bad;
1817 	}
1818 
1819 	while (c->need_reserved_buffers) {
1820 		struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1821 
1822 		if (!b) {
1823 			r = -ENOMEM;
1824 			goto bad;
1825 		}
1826 		__free_buffer_wake(b);
1827 	}
1828 
1829 	INIT_WORK(&c->shrink_work, shrink_work);
1830 	atomic_long_set(&c->need_shrink, 0);
1831 
1832 	c->shrinker.count_objects = dm_bufio_shrink_count;
1833 	c->shrinker.scan_objects = dm_bufio_shrink_scan;
1834 	c->shrinker.seeks = 1;
1835 	c->shrinker.batch = 0;
1836 	r = register_shrinker(&c->shrinker, "md-%s:(%u:%u)", slab_name,
1837 			      MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
1838 	if (r)
1839 		goto bad;
1840 
1841 	mutex_lock(&dm_bufio_clients_lock);
1842 	dm_bufio_client_count++;
1843 	list_add(&c->client_list, &dm_bufio_all_clients);
1844 	__cache_size_refresh();
1845 	mutex_unlock(&dm_bufio_clients_lock);
1846 
1847 	return c;
1848 
1849 bad:
1850 	while (!list_empty(&c->reserved_buffers)) {
1851 		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1852 						 struct dm_buffer, lru_list);
1853 		list_del(&b->lru_list);
1854 		free_buffer(b);
1855 	}
1856 	kmem_cache_destroy(c->slab_cache);
1857 	kmem_cache_destroy(c->slab_buffer);
1858 	dm_io_client_destroy(c->dm_io);
1859 bad_dm_io:
1860 	mutex_destroy(&c->lock);
1861 	if (c->no_sleep)
1862 		static_branch_dec(&no_sleep_enabled);
1863 	kfree(c);
1864 bad_client:
1865 	return ERR_PTR(r);
1866 }
1867 EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1868 
1869 /*
1870  * Free the buffering interface.
1871  * It is required that there are no references on any buffers.
1872  */
dm_bufio_client_destroy(struct dm_bufio_client * c)1873 void dm_bufio_client_destroy(struct dm_bufio_client *c)
1874 {
1875 	unsigned i;
1876 
1877 	drop_buffers(c);
1878 
1879 	unregister_shrinker(&c->shrinker);
1880 	flush_work(&c->shrink_work);
1881 
1882 	mutex_lock(&dm_bufio_clients_lock);
1883 
1884 	list_del(&c->client_list);
1885 	dm_bufio_client_count--;
1886 	__cache_size_refresh();
1887 
1888 	mutex_unlock(&dm_bufio_clients_lock);
1889 
1890 	BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1891 	BUG_ON(c->need_reserved_buffers);
1892 
1893 	while (!list_empty(&c->reserved_buffers)) {
1894 		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1895 						 struct dm_buffer, lru_list);
1896 		list_del(&b->lru_list);
1897 		free_buffer(b);
1898 	}
1899 
1900 	for (i = 0; i < LIST_SIZE; i++)
1901 		if (c->n_buffers[i])
1902 			DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1903 
1904 	for (i = 0; i < LIST_SIZE; i++)
1905 		BUG_ON(c->n_buffers[i]);
1906 
1907 	kmem_cache_destroy(c->slab_cache);
1908 	kmem_cache_destroy(c->slab_buffer);
1909 	dm_io_client_destroy(c->dm_io);
1910 	mutex_destroy(&c->lock);
1911 	if (c->no_sleep)
1912 		static_branch_dec(&no_sleep_enabled);
1913 	kfree(c);
1914 }
1915 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1916 
dm_bufio_set_sector_offset(struct dm_bufio_client * c,sector_t start)1917 void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1918 {
1919 	c->start = start;
1920 }
1921 EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1922 
get_max_age_hz(void)1923 static unsigned get_max_age_hz(void)
1924 {
1925 	unsigned max_age = READ_ONCE(dm_bufio_max_age);
1926 
1927 	if (max_age > UINT_MAX / HZ)
1928 		max_age = UINT_MAX / HZ;
1929 
1930 	return max_age * HZ;
1931 }
1932 
older_than(struct dm_buffer * b,unsigned long age_hz)1933 static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1934 {
1935 	return time_after_eq(jiffies, b->last_accessed + age_hz);
1936 }
1937 
__evict_old_buffers(struct dm_bufio_client * c,unsigned long age_hz)1938 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1939 {
1940 	struct dm_buffer *b, *tmp;
1941 	unsigned long retain_target = get_retain_buffers(c);
1942 	unsigned long count;
1943 	LIST_HEAD(write_list);
1944 
1945 	dm_bufio_lock(c);
1946 
1947 	__check_watermark(c, &write_list);
1948 	if (unlikely(!list_empty(&write_list))) {
1949 		dm_bufio_unlock(c);
1950 		__flush_write_list(&write_list);
1951 		dm_bufio_lock(c);
1952 	}
1953 
1954 	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1955 	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1956 		if (count <= retain_target)
1957 			break;
1958 
1959 		if (!older_than(b, age_hz))
1960 			break;
1961 
1962 		if (__try_evict_buffer(b, 0))
1963 			count--;
1964 
1965 		cond_resched();
1966 	}
1967 
1968 	dm_bufio_unlock(c);
1969 }
1970 
do_global_cleanup(struct work_struct * w)1971 static void do_global_cleanup(struct work_struct *w)
1972 {
1973 	struct dm_bufio_client *locked_client = NULL;
1974 	struct dm_bufio_client *current_client;
1975 	struct dm_buffer *b;
1976 	unsigned spinlock_hold_count;
1977 	unsigned long threshold = dm_bufio_cache_size -
1978 		dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
1979 	unsigned long loops = global_num * 2;
1980 
1981 	mutex_lock(&dm_bufio_clients_lock);
1982 
1983 	while (1) {
1984 		cond_resched();
1985 
1986 		spin_lock(&global_spinlock);
1987 		if (unlikely(dm_bufio_current_allocated <= threshold))
1988 			break;
1989 
1990 		spinlock_hold_count = 0;
1991 get_next:
1992 		if (!loops--)
1993 			break;
1994 		if (unlikely(list_empty(&global_queue)))
1995 			break;
1996 		b = list_entry(global_queue.prev, struct dm_buffer, global_list);
1997 
1998 		if (b->accessed) {
1999 			b->accessed = 0;
2000 			list_move(&b->global_list, &global_queue);
2001 			if (likely(++spinlock_hold_count < 16))
2002 				goto get_next;
2003 			spin_unlock(&global_spinlock);
2004 			continue;
2005 		}
2006 
2007 		current_client = b->c;
2008 		if (unlikely(current_client != locked_client)) {
2009 			if (locked_client)
2010 				dm_bufio_unlock(locked_client);
2011 
2012 			if (!dm_bufio_trylock(current_client)) {
2013 				spin_unlock(&global_spinlock);
2014 				dm_bufio_lock(current_client);
2015 				locked_client = current_client;
2016 				continue;
2017 			}
2018 
2019 			locked_client = current_client;
2020 		}
2021 
2022 		spin_unlock(&global_spinlock);
2023 
2024 		if (unlikely(!__try_evict_buffer(b, GFP_KERNEL))) {
2025 			spin_lock(&global_spinlock);
2026 			list_move(&b->global_list, &global_queue);
2027 			spin_unlock(&global_spinlock);
2028 		}
2029 	}
2030 
2031 	spin_unlock(&global_spinlock);
2032 
2033 	if (locked_client)
2034 		dm_bufio_unlock(locked_client);
2035 
2036 	mutex_unlock(&dm_bufio_clients_lock);
2037 }
2038 
cleanup_old_buffers(void)2039 static void cleanup_old_buffers(void)
2040 {
2041 	unsigned long max_age_hz = get_max_age_hz();
2042 	struct dm_bufio_client *c;
2043 
2044 	mutex_lock(&dm_bufio_clients_lock);
2045 
2046 	__cache_size_refresh();
2047 
2048 	list_for_each_entry(c, &dm_bufio_all_clients, client_list)
2049 		__evict_old_buffers(c, max_age_hz);
2050 
2051 	mutex_unlock(&dm_bufio_clients_lock);
2052 }
2053 
work_fn(struct work_struct * w)2054 static void work_fn(struct work_struct *w)
2055 {
2056 	cleanup_old_buffers();
2057 
2058 	queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2059 			   DM_BUFIO_WORK_TIMER_SECS * HZ);
2060 }
2061 
2062 /*----------------------------------------------------------------
2063  * Module setup
2064  *--------------------------------------------------------------*/
2065 
2066 /*
2067  * This is called only once for the whole dm_bufio module.
2068  * It initializes memory limit.
2069  */
dm_bufio_init(void)2070 static int __init dm_bufio_init(void)
2071 {
2072 	__u64 mem;
2073 
2074 	dm_bufio_allocated_kmem_cache = 0;
2075 	dm_bufio_allocated_get_free_pages = 0;
2076 	dm_bufio_allocated_vmalloc = 0;
2077 	dm_bufio_current_allocated = 0;
2078 
2079 	mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
2080 			       DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
2081 
2082 	if (mem > ULONG_MAX)
2083 		mem = ULONG_MAX;
2084 
2085 #ifdef CONFIG_MMU
2086 	if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
2087 		mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
2088 #endif
2089 
2090 	dm_bufio_default_cache_size = mem;
2091 
2092 	mutex_lock(&dm_bufio_clients_lock);
2093 	__cache_size_refresh();
2094 	mutex_unlock(&dm_bufio_clients_lock);
2095 
2096 	dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
2097 	if (!dm_bufio_wq)
2098 		return -ENOMEM;
2099 
2100 	INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
2101 	INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
2102 	queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2103 			   DM_BUFIO_WORK_TIMER_SECS * HZ);
2104 
2105 	return 0;
2106 }
2107 
2108 /*
2109  * This is called once when unloading the dm_bufio module.
2110  */
dm_bufio_exit(void)2111 static void __exit dm_bufio_exit(void)
2112 {
2113 	int bug = 0;
2114 
2115 	cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
2116 	destroy_workqueue(dm_bufio_wq);
2117 
2118 	if (dm_bufio_client_count) {
2119 		DMCRIT("%s: dm_bufio_client_count leaked: %d",
2120 			__func__, dm_bufio_client_count);
2121 		bug = 1;
2122 	}
2123 
2124 	if (dm_bufio_current_allocated) {
2125 		DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
2126 			__func__, dm_bufio_current_allocated);
2127 		bug = 1;
2128 	}
2129 
2130 	if (dm_bufio_allocated_get_free_pages) {
2131 		DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
2132 		       __func__, dm_bufio_allocated_get_free_pages);
2133 		bug = 1;
2134 	}
2135 
2136 	if (dm_bufio_allocated_vmalloc) {
2137 		DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
2138 		       __func__, dm_bufio_allocated_vmalloc);
2139 		bug = 1;
2140 	}
2141 
2142 	BUG_ON(bug);
2143 }
2144 
2145 module_init(dm_bufio_init)
2146 module_exit(dm_bufio_exit)
2147 
2148 module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
2149 MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
2150 
2151 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
2152 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
2153 
2154 module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
2155 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2156 
2157 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
2158 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
2159 
2160 module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
2161 MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
2162 
2163 module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
2164 MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
2165 
2166 module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
2167 MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
2168 
2169 module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
2170 MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
2171 
2172 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2173 MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
2174 MODULE_LICENSE("GPL");
2175