1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2002 Sistina Software (UK) Limited.
4 * Copyright (C) 2006 Red Hat GmbH
5 *
6 * This file is released under the GPL.
7 *
8 * Kcopyd provides a simple interface for copying an area of one
9 * block-device to one or more other block-devices, with an asynchronous
10 * completion notification.
11 */
12
13#include <linux/types.h>
14#include <linux/atomic.h>
15#include <linux/blkdev.h>
16#include <linux/fs.h>
17#include <linux/init.h>
18#include <linux/list.h>
19#include <linux/mempool.h>
20#include <linux/module.h>
21#include <linux/pagemap.h>
22#include <linux/slab.h>
23#include <linux/vmalloc.h>
24#include <linux/workqueue.h>
25#include <linux/mutex.h>
26#include <linux/delay.h>
27#include <linux/device-mapper.h>
28#include <linux/dm-kcopyd.h>
29
30#include "dm-core.h"
31
32#define SPLIT_COUNT	8
33#define MIN_JOBS	8
34
35#define DEFAULT_SUB_JOB_SIZE_KB 512
36#define MAX_SUB_JOB_SIZE_KB     1024
37
38static unsigned int kcopyd_subjob_size_kb = DEFAULT_SUB_JOB_SIZE_KB;
39
40module_param(kcopyd_subjob_size_kb, uint, 0644);
41MODULE_PARM_DESC(kcopyd_subjob_size_kb, "Sub-job size for dm-kcopyd clients");
42
43static unsigned int dm_get_kcopyd_subjob_size(void)
44{
45	unsigned int sub_job_size_kb;
46
47	sub_job_size_kb = __dm_get_module_param(&kcopyd_subjob_size_kb,
48						DEFAULT_SUB_JOB_SIZE_KB,
49						MAX_SUB_JOB_SIZE_KB);
50
51	return sub_job_size_kb << 1;
52}
53
54/*
55 *----------------------------------------------------------------
56 * Each kcopyd client has its own little pool of preallocated
57 * pages for kcopyd io.
58 *---------------------------------------------------------------
59 */
60struct dm_kcopyd_client {
61	struct page_list *pages;
62	unsigned int nr_reserved_pages;
63	unsigned int nr_free_pages;
64	unsigned int sub_job_size;
65
66	struct dm_io_client *io_client;
67
68	wait_queue_head_t destroyq;
69
70	mempool_t job_pool;
71
72	struct workqueue_struct *kcopyd_wq;
73	struct work_struct kcopyd_work;
74
75	struct dm_kcopyd_throttle *throttle;
76
77	atomic_t nr_jobs;
78
79/*
80 * We maintain four lists of jobs:
81 *
82 * i)   jobs waiting for pages
83 * ii)  jobs that have pages, and are waiting for the io to be issued.
84 * iii) jobs that don't need to do any IO and just run a callback
85 * iv) jobs that have completed.
86 *
87 * All four of these are protected by job_lock.
88 */
89	spinlock_t job_lock;
90	struct list_head callback_jobs;
91	struct list_head complete_jobs;
92	struct list_head io_jobs;
93	struct list_head pages_jobs;
94};
95
96static struct page_list zero_page_list;
97
98static DEFINE_SPINLOCK(throttle_spinlock);
99
100/*
101 * IO/IDLE accounting slowly decays after (1 << ACCOUNT_INTERVAL_SHIFT) period.
102 * When total_period >= (1 << ACCOUNT_INTERVAL_SHIFT) the counters are divided
103 * by 2.
104 */
105#define ACCOUNT_INTERVAL_SHIFT		SHIFT_HZ
106
107/*
108 * Sleep this number of milliseconds.
109 *
110 * The value was decided experimentally.
111 * Smaller values seem to cause an increased copy rate above the limit.
112 * The reason for this is unknown but possibly due to jiffies rounding errors
113 * or read/write cache inside the disk.
114 */
115#define SLEEP_USEC			100000
116
117/*
118 * Maximum number of sleep events. There is a theoretical livelock if more
119 * kcopyd clients do work simultaneously which this limit avoids.
120 */
121#define MAX_SLEEPS			10
122
123static void io_job_start(struct dm_kcopyd_throttle *t)
124{
125	unsigned int throttle, now, difference;
126	int slept = 0, skew;
127
128	if (unlikely(!t))
129		return;
130
131try_again:
132	spin_lock_irq(&throttle_spinlock);
133
134	throttle = READ_ONCE(t->throttle);
135
136	if (likely(throttle >= 100))
137		goto skip_limit;
138
139	now = jiffies;
140	difference = now - t->last_jiffies;
141	t->last_jiffies = now;
142	if (t->num_io_jobs)
143		t->io_period += difference;
144	t->total_period += difference;
145
146	/*
147	 * Maintain sane values if we got a temporary overflow.
148	 */
149	if (unlikely(t->io_period > t->total_period))
150		t->io_period = t->total_period;
151
152	if (unlikely(t->total_period >= (1 << ACCOUNT_INTERVAL_SHIFT))) {
153		int shift = fls(t->total_period >> ACCOUNT_INTERVAL_SHIFT);
154
155		t->total_period >>= shift;
156		t->io_period >>= shift;
157	}
158
159	skew = t->io_period - throttle * t->total_period / 100;
160
161	if (unlikely(skew > 0) && slept < MAX_SLEEPS) {
162		slept++;
163		spin_unlock_irq(&throttle_spinlock);
164		fsleep(SLEEP_USEC);
165		goto try_again;
166	}
167
168skip_limit:
169	t->num_io_jobs++;
170
171	spin_unlock_irq(&throttle_spinlock);
172}
173
174static void io_job_finish(struct dm_kcopyd_throttle *t)
175{
176	unsigned long flags;
177
178	if (unlikely(!t))
179		return;
180
181	spin_lock_irqsave(&throttle_spinlock, flags);
182
183	t->num_io_jobs--;
184
185	if (likely(READ_ONCE(t->throttle) >= 100))
186		goto skip_limit;
187
188	if (!t->num_io_jobs) {
189		unsigned int now, difference;
190
191		now = jiffies;
192		difference = now - t->last_jiffies;
193		t->last_jiffies = now;
194
195		t->io_period += difference;
196		t->total_period += difference;
197
198		/*
199		 * Maintain sane values if we got a temporary overflow.
200		 */
201		if (unlikely(t->io_period > t->total_period))
202			t->io_period = t->total_period;
203	}
204
205skip_limit:
206	spin_unlock_irqrestore(&throttle_spinlock, flags);
207}
208
209
210static void wake(struct dm_kcopyd_client *kc)
211{
212	queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
213}
214
215/*
216 * Obtain one page for the use of kcopyd.
217 */
218static struct page_list *alloc_pl(gfp_t gfp)
219{
220	struct page_list *pl;
221
222	pl = kmalloc(sizeof(*pl), gfp);
223	if (!pl)
224		return NULL;
225
226	pl->page = alloc_page(gfp | __GFP_HIGHMEM);
227	if (!pl->page) {
228		kfree(pl);
229		return NULL;
230	}
231
232	return pl;
233}
234
235static void free_pl(struct page_list *pl)
236{
237	__free_page(pl->page);
238	kfree(pl);
239}
240
241/*
242 * Add the provided pages to a client's free page list, releasing
243 * back to the system any beyond the reserved_pages limit.
244 */
245static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
246{
247	struct page_list *next;
248
249	do {
250		next = pl->next;
251
252		if (kc->nr_free_pages >= kc->nr_reserved_pages)
253			free_pl(pl);
254		else {
255			pl->next = kc->pages;
256			kc->pages = pl;
257			kc->nr_free_pages++;
258		}
259
260		pl = next;
261	} while (pl);
262}
263
264static int kcopyd_get_pages(struct dm_kcopyd_client *kc,
265			    unsigned int nr, struct page_list **pages)
266{
267	struct page_list *pl;
268
269	*pages = NULL;
270
271	do {
272		pl = alloc_pl(__GFP_NOWARN | __GFP_NORETRY | __GFP_KSWAPD_RECLAIM);
273		if (unlikely(!pl)) {
274			/* Use reserved pages */
275			pl = kc->pages;
276			if (unlikely(!pl))
277				goto out_of_memory;
278			kc->pages = pl->next;
279			kc->nr_free_pages--;
280		}
281		pl->next = *pages;
282		*pages = pl;
283	} while (--nr);
284
285	return 0;
286
287out_of_memory:
288	if (*pages)
289		kcopyd_put_pages(kc, *pages);
290	return -ENOMEM;
291}
292
293/*
294 * These three functions resize the page pool.
295 */
296static void drop_pages(struct page_list *pl)
297{
298	struct page_list *next;
299
300	while (pl) {
301		next = pl->next;
302		free_pl(pl);
303		pl = next;
304	}
305}
306
307/*
308 * Allocate and reserve nr_pages for the use of a specific client.
309 */
310static int client_reserve_pages(struct dm_kcopyd_client *kc, unsigned int nr_pages)
311{
312	unsigned int i;
313	struct page_list *pl = NULL, *next;
314
315	for (i = 0; i < nr_pages; i++) {
316		next = alloc_pl(GFP_KERNEL);
317		if (!next) {
318			if (pl)
319				drop_pages(pl);
320			return -ENOMEM;
321		}
322		next->next = pl;
323		pl = next;
324	}
325
326	kc->nr_reserved_pages += nr_pages;
327	kcopyd_put_pages(kc, pl);
328
329	return 0;
330}
331
332static void client_free_pages(struct dm_kcopyd_client *kc)
333{
334	BUG_ON(kc->nr_free_pages != kc->nr_reserved_pages);
335	drop_pages(kc->pages);
336	kc->pages = NULL;
337	kc->nr_free_pages = kc->nr_reserved_pages = 0;
338}
339
340/*
341 *---------------------------------------------------------------
342 * kcopyd_jobs need to be allocated by the *clients* of kcopyd,
343 * for this reason we use a mempool to prevent the client from
344 * ever having to do io (which could cause a deadlock).
345 *---------------------------------------------------------------
346 */
347struct kcopyd_job {
348	struct dm_kcopyd_client *kc;
349	struct list_head list;
350	unsigned int flags;
351
352	/*
353	 * Error state of the job.
354	 */
355	int read_err;
356	unsigned long write_err;
357
358	/*
359	 * REQ_OP_READ, REQ_OP_WRITE or REQ_OP_WRITE_ZEROES.
360	 */
361	enum req_op op;
362	struct dm_io_region source;
363
364	/*
365	 * The destinations for the transfer.
366	 */
367	unsigned int num_dests;
368	struct dm_io_region dests[DM_KCOPYD_MAX_REGIONS];
369
370	struct page_list *pages;
371
372	/*
373	 * Set this to ensure you are notified when the job has
374	 * completed.  'context' is for callback to use.
375	 */
376	dm_kcopyd_notify_fn fn;
377	void *context;
378
379	/*
380	 * These fields are only used if the job has been split
381	 * into more manageable parts.
382	 */
383	struct mutex lock;
384	atomic_t sub_jobs;
385	sector_t progress;
386	sector_t write_offset;
387
388	struct kcopyd_job *master_job;
389};
390
391static struct kmem_cache *_job_cache;
392
393int __init dm_kcopyd_init(void)
394{
395	_job_cache = kmem_cache_create("kcopyd_job",
396				sizeof(struct kcopyd_job) * (SPLIT_COUNT + 1),
397				__alignof__(struct kcopyd_job), 0, NULL);
398	if (!_job_cache)
399		return -ENOMEM;
400
401	zero_page_list.next = &zero_page_list;
402	zero_page_list.page = ZERO_PAGE(0);
403
404	return 0;
405}
406
407void dm_kcopyd_exit(void)
408{
409	kmem_cache_destroy(_job_cache);
410	_job_cache = NULL;
411}
412
413/*
414 * Functions to push and pop a job onto the head of a given job
415 * list.
416 */
417static struct kcopyd_job *pop_io_job(struct list_head *jobs,
418				     struct dm_kcopyd_client *kc)
419{
420	struct kcopyd_job *job;
421
422	/*
423	 * For I/O jobs, pop any read, any write without sequential write
424	 * constraint and sequential writes that are at the right position.
425	 */
426	list_for_each_entry(job, jobs, list) {
427		if (job->op == REQ_OP_READ ||
428		    !(job->flags & BIT(DM_KCOPYD_WRITE_SEQ))) {
429			list_del(&job->list);
430			return job;
431		}
432
433		if (job->write_offset == job->master_job->write_offset) {
434			job->master_job->write_offset += job->source.count;
435			list_del(&job->list);
436			return job;
437		}
438	}
439
440	return NULL;
441}
442
443static struct kcopyd_job *pop(struct list_head *jobs,
444			      struct dm_kcopyd_client *kc)
445{
446	struct kcopyd_job *job = NULL;
447
448	spin_lock_irq(&kc->job_lock);
449
450	if (!list_empty(jobs)) {
451		if (jobs == &kc->io_jobs)
452			job = pop_io_job(jobs, kc);
453		else {
454			job = list_entry(jobs->next, struct kcopyd_job, list);
455			list_del(&job->list);
456		}
457	}
458	spin_unlock_irq(&kc->job_lock);
459
460	return job;
461}
462
463static void push(struct list_head *jobs, struct kcopyd_job *job)
464{
465	unsigned long flags;
466	struct dm_kcopyd_client *kc = job->kc;
467
468	spin_lock_irqsave(&kc->job_lock, flags);
469	list_add_tail(&job->list, jobs);
470	spin_unlock_irqrestore(&kc->job_lock, flags);
471}
472
473
474static void push_head(struct list_head *jobs, struct kcopyd_job *job)
475{
476	struct dm_kcopyd_client *kc = job->kc;
477
478	spin_lock_irq(&kc->job_lock);
479	list_add(&job->list, jobs);
480	spin_unlock_irq(&kc->job_lock);
481}
482
483/*
484 * These three functions process 1 item from the corresponding
485 * job list.
486 *
487 * They return:
488 * < 0: error
489 *   0: success
490 * > 0: can't process yet.
491 */
492static int run_complete_job(struct kcopyd_job *job)
493{
494	void *context = job->context;
495	int read_err = job->read_err;
496	unsigned long write_err = job->write_err;
497	dm_kcopyd_notify_fn fn = job->fn;
498	struct dm_kcopyd_client *kc = job->kc;
499
500	if (job->pages && job->pages != &zero_page_list)
501		kcopyd_put_pages(kc, job->pages);
502	/*
503	 * If this is the master job, the sub jobs have already
504	 * completed so we can free everything.
505	 */
506	if (job->master_job == job) {
507		mutex_destroy(&job->lock);
508		mempool_free(job, &kc->job_pool);
509	}
510	fn(read_err, write_err, context);
511
512	if (atomic_dec_and_test(&kc->nr_jobs))
513		wake_up(&kc->destroyq);
514
515	cond_resched();
516
517	return 0;
518}
519
520static void complete_io(unsigned long error, void *context)
521{
522	struct kcopyd_job *job = context;
523	struct dm_kcopyd_client *kc = job->kc;
524
525	io_job_finish(kc->throttle);
526
527	if (error) {
528		if (op_is_write(job->op))
529			job->write_err |= error;
530		else
531			job->read_err = 1;
532
533		if (!(job->flags & BIT(DM_KCOPYD_IGNORE_ERROR))) {
534			push(&kc->complete_jobs, job);
535			wake(kc);
536			return;
537		}
538	}
539
540	if (op_is_write(job->op))
541		push(&kc->complete_jobs, job);
542
543	else {
544		job->op = REQ_OP_WRITE;
545		push(&kc->io_jobs, job);
546	}
547
548	wake(kc);
549}
550
551/*
552 * Request io on as many buffer heads as we can currently get for
553 * a particular job.
554 */
555static int run_io_job(struct kcopyd_job *job)
556{
557	int r;
558	struct dm_io_request io_req = {
559		.bi_opf = job->op,
560		.mem.type = DM_IO_PAGE_LIST,
561		.mem.ptr.pl = job->pages,
562		.mem.offset = 0,
563		.notify.fn = complete_io,
564		.notify.context = job,
565		.client = job->kc->io_client,
566	};
567
568	/*
569	 * If we need to write sequentially and some reads or writes failed,
570	 * no point in continuing.
571	 */
572	if (job->flags & BIT(DM_KCOPYD_WRITE_SEQ) &&
573	    job->master_job->write_err) {
574		job->write_err = job->master_job->write_err;
575		return -EIO;
576	}
577
578	io_job_start(job->kc->throttle);
579
580	if (job->op == REQ_OP_READ)
581		r = dm_io(&io_req, 1, &job->source, NULL, IOPRIO_DEFAULT);
582	else
583		r = dm_io(&io_req, job->num_dests, job->dests, NULL, IOPRIO_DEFAULT);
584
585	return r;
586}
587
588static int run_pages_job(struct kcopyd_job *job)
589{
590	int r;
591	unsigned int nr_pages = dm_div_up(job->dests[0].count, PAGE_SIZE >> 9);
592
593	r = kcopyd_get_pages(job->kc, nr_pages, &job->pages);
594	if (!r) {
595		/* this job is ready for io */
596		push(&job->kc->io_jobs, job);
597		return 0;
598	}
599
600	if (r == -ENOMEM)
601		/* can't complete now */
602		return 1;
603
604	return r;
605}
606
607/*
608 * Run through a list for as long as possible.  Returns the count
609 * of successful jobs.
610 */
611static int process_jobs(struct list_head *jobs, struct dm_kcopyd_client *kc,
612			int (*fn)(struct kcopyd_job *))
613{
614	struct kcopyd_job *job;
615	int r, count = 0;
616
617	while ((job = pop(jobs, kc))) {
618
619		r = fn(job);
620
621		if (r < 0) {
622			/* error this rogue job */
623			if (op_is_write(job->op))
624				job->write_err = (unsigned long) -1L;
625			else
626				job->read_err = 1;
627			push(&kc->complete_jobs, job);
628			wake(kc);
629			break;
630		}
631
632		if (r > 0) {
633			/*
634			 * We couldn't service this job ATM, so
635			 * push this job back onto the list.
636			 */
637			push_head(jobs, job);
638			break;
639		}
640
641		count++;
642	}
643
644	return count;
645}
646
647/*
648 * kcopyd does this every time it's woken up.
649 */
650static void do_work(struct work_struct *work)
651{
652	struct dm_kcopyd_client *kc = container_of(work,
653					struct dm_kcopyd_client, kcopyd_work);
654	struct blk_plug plug;
655
656	/*
657	 * The order that these are called is *very* important.
658	 * complete jobs can free some pages for pages jobs.
659	 * Pages jobs when successful will jump onto the io jobs
660	 * list.  io jobs call wake when they complete and it all
661	 * starts again.
662	 */
663	spin_lock_irq(&kc->job_lock);
664	list_splice_tail_init(&kc->callback_jobs, &kc->complete_jobs);
665	spin_unlock_irq(&kc->job_lock);
666
667	blk_start_plug(&plug);
668	process_jobs(&kc->complete_jobs, kc, run_complete_job);
669	process_jobs(&kc->pages_jobs, kc, run_pages_job);
670	process_jobs(&kc->io_jobs, kc, run_io_job);
671	blk_finish_plug(&plug);
672}
673
674/*
675 * If we are copying a small region we just dispatch a single job
676 * to do the copy, otherwise the io has to be split up into many
677 * jobs.
678 */
679static void dispatch_job(struct kcopyd_job *job)
680{
681	struct dm_kcopyd_client *kc = job->kc;
682
683	atomic_inc(&kc->nr_jobs);
684	if (unlikely(!job->source.count))
685		push(&kc->callback_jobs, job);
686	else if (job->pages == &zero_page_list)
687		push(&kc->io_jobs, job);
688	else
689		push(&kc->pages_jobs, job);
690	wake(kc);
691}
692
693static void segment_complete(int read_err, unsigned long write_err,
694			     void *context)
695{
696	/* FIXME: tidy this function */
697	sector_t progress = 0;
698	sector_t count = 0;
699	struct kcopyd_job *sub_job = context;
700	struct kcopyd_job *job = sub_job->master_job;
701	struct dm_kcopyd_client *kc = job->kc;
702
703	mutex_lock(&job->lock);
704
705	/* update the error */
706	if (read_err)
707		job->read_err = 1;
708
709	if (write_err)
710		job->write_err |= write_err;
711
712	/*
713	 * Only dispatch more work if there hasn't been an error.
714	 */
715	if ((!job->read_err && !job->write_err) ||
716	    job->flags & BIT(DM_KCOPYD_IGNORE_ERROR)) {
717		/* get the next chunk of work */
718		progress = job->progress;
719		count = job->source.count - progress;
720		if (count) {
721			if (count > kc->sub_job_size)
722				count = kc->sub_job_size;
723
724			job->progress += count;
725		}
726	}
727	mutex_unlock(&job->lock);
728
729	if (count) {
730		int i;
731
732		*sub_job = *job;
733		sub_job->write_offset = progress;
734		sub_job->source.sector += progress;
735		sub_job->source.count = count;
736
737		for (i = 0; i < job->num_dests; i++) {
738			sub_job->dests[i].sector += progress;
739			sub_job->dests[i].count = count;
740		}
741
742		sub_job->fn = segment_complete;
743		sub_job->context = sub_job;
744		dispatch_job(sub_job);
745
746	} else if (atomic_dec_and_test(&job->sub_jobs)) {
747
748		/*
749		 * Queue the completion callback to the kcopyd thread.
750		 *
751		 * Some callers assume that all the completions are called
752		 * from a single thread and don't race with each other.
753		 *
754		 * We must not call the callback directly here because this
755		 * code may not be executing in the thread.
756		 */
757		push(&kc->complete_jobs, job);
758		wake(kc);
759	}
760}
761
762/*
763 * Create some sub jobs to share the work between them.
764 */
765static void split_job(struct kcopyd_job *master_job)
766{
767	int i;
768
769	atomic_inc(&master_job->kc->nr_jobs);
770
771	atomic_set(&master_job->sub_jobs, SPLIT_COUNT);
772	for (i = 0; i < SPLIT_COUNT; i++) {
773		master_job[i + 1].master_job = master_job;
774		segment_complete(0, 0u, &master_job[i + 1]);
775	}
776}
777
778void dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
779		    unsigned int num_dests, struct dm_io_region *dests,
780		    unsigned int flags, dm_kcopyd_notify_fn fn, void *context)
781{
782	struct kcopyd_job *job;
783	int i;
784
785	/*
786	 * Allocate an array of jobs consisting of one master job
787	 * followed by SPLIT_COUNT sub jobs.
788	 */
789	job = mempool_alloc(&kc->job_pool, GFP_NOIO);
790	mutex_init(&job->lock);
791
792	/*
793	 * set up for the read.
794	 */
795	job->kc = kc;
796	job->flags = flags;
797	job->read_err = 0;
798	job->write_err = 0;
799
800	job->num_dests = num_dests;
801	memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
802
803	/*
804	 * If one of the destination is a host-managed zoned block device,
805	 * we need to write sequentially. If one of the destination is a
806	 * host-aware device, then leave it to the caller to choose what to do.
807	 */
808	if (!(job->flags & BIT(DM_KCOPYD_WRITE_SEQ))) {
809		for (i = 0; i < job->num_dests; i++) {
810			if (bdev_is_zoned(dests[i].bdev)) {
811				job->flags |= BIT(DM_KCOPYD_WRITE_SEQ);
812				break;
813			}
814		}
815	}
816
817	/*
818	 * If we need to write sequentially, errors cannot be ignored.
819	 */
820	if (job->flags & BIT(DM_KCOPYD_WRITE_SEQ) &&
821	    job->flags & BIT(DM_KCOPYD_IGNORE_ERROR))
822		job->flags &= ~BIT(DM_KCOPYD_IGNORE_ERROR);
823
824	if (from) {
825		job->source = *from;
826		job->pages = NULL;
827		job->op = REQ_OP_READ;
828	} else {
829		memset(&job->source, 0, sizeof(job->source));
830		job->source.count = job->dests[0].count;
831		job->pages = &zero_page_list;
832
833		/*
834		 * Use WRITE ZEROES to optimize zeroing if all dests support it.
835		 */
836		job->op = REQ_OP_WRITE_ZEROES;
837		for (i = 0; i < job->num_dests; i++)
838			if (!bdev_write_zeroes_sectors(job->dests[i].bdev)) {
839				job->op = REQ_OP_WRITE;
840				break;
841			}
842	}
843
844	job->fn = fn;
845	job->context = context;
846	job->master_job = job;
847	job->write_offset = 0;
848
849	if (job->source.count <= kc->sub_job_size)
850		dispatch_job(job);
851	else {
852		job->progress = 0;
853		split_job(job);
854	}
855}
856EXPORT_SYMBOL(dm_kcopyd_copy);
857
858void dm_kcopyd_zero(struct dm_kcopyd_client *kc,
859		    unsigned int num_dests, struct dm_io_region *dests,
860		    unsigned int flags, dm_kcopyd_notify_fn fn, void *context)
861{
862	dm_kcopyd_copy(kc, NULL, num_dests, dests, flags, fn, context);
863}
864EXPORT_SYMBOL(dm_kcopyd_zero);
865
866void *dm_kcopyd_prepare_callback(struct dm_kcopyd_client *kc,
867				 dm_kcopyd_notify_fn fn, void *context)
868{
869	struct kcopyd_job *job;
870
871	job = mempool_alloc(&kc->job_pool, GFP_NOIO);
872
873	memset(job, 0, sizeof(struct kcopyd_job));
874	job->kc = kc;
875	job->fn = fn;
876	job->context = context;
877	job->master_job = job;
878
879	atomic_inc(&kc->nr_jobs);
880
881	return job;
882}
883EXPORT_SYMBOL(dm_kcopyd_prepare_callback);
884
885void dm_kcopyd_do_callback(void *j, int read_err, unsigned long write_err)
886{
887	struct kcopyd_job *job = j;
888	struct dm_kcopyd_client *kc = job->kc;
889
890	job->read_err = read_err;
891	job->write_err = write_err;
892
893	push(&kc->callback_jobs, job);
894	wake(kc);
895}
896EXPORT_SYMBOL(dm_kcopyd_do_callback);
897
898/*
899 * Cancels a kcopyd job, eg. someone might be deactivating a
900 * mirror.
901 */
902#if 0
903int kcopyd_cancel(struct kcopyd_job *job, int block)
904{
905	/* FIXME: finish */
906	return -1;
907}
908#endif  /*  0  */
909
910/*
911 *---------------------------------------------------------------
912 * Client setup
913 *---------------------------------------------------------------
914 */
915struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle)
916{
917	int r;
918	unsigned int reserve_pages;
919	struct dm_kcopyd_client *kc;
920
921	kc = kzalloc(sizeof(*kc), GFP_KERNEL);
922	if (!kc)
923		return ERR_PTR(-ENOMEM);
924
925	spin_lock_init(&kc->job_lock);
926	INIT_LIST_HEAD(&kc->callback_jobs);
927	INIT_LIST_HEAD(&kc->complete_jobs);
928	INIT_LIST_HEAD(&kc->io_jobs);
929	INIT_LIST_HEAD(&kc->pages_jobs);
930	kc->throttle = throttle;
931
932	r = mempool_init_slab_pool(&kc->job_pool, MIN_JOBS, _job_cache);
933	if (r)
934		goto bad_slab;
935
936	INIT_WORK(&kc->kcopyd_work, do_work);
937	kc->kcopyd_wq = alloc_workqueue("kcopyd", WQ_MEM_RECLAIM, 0);
938	if (!kc->kcopyd_wq) {
939		r = -ENOMEM;
940		goto bad_workqueue;
941	}
942
943	kc->sub_job_size = dm_get_kcopyd_subjob_size();
944	reserve_pages = DIV_ROUND_UP(kc->sub_job_size << SECTOR_SHIFT, PAGE_SIZE);
945
946	kc->pages = NULL;
947	kc->nr_reserved_pages = kc->nr_free_pages = 0;
948	r = client_reserve_pages(kc, reserve_pages);
949	if (r)
950		goto bad_client_pages;
951
952	kc->io_client = dm_io_client_create();
953	if (IS_ERR(kc->io_client)) {
954		r = PTR_ERR(kc->io_client);
955		goto bad_io_client;
956	}
957
958	init_waitqueue_head(&kc->destroyq);
959	atomic_set(&kc->nr_jobs, 0);
960
961	return kc;
962
963bad_io_client:
964	client_free_pages(kc);
965bad_client_pages:
966	destroy_workqueue(kc->kcopyd_wq);
967bad_workqueue:
968	mempool_exit(&kc->job_pool);
969bad_slab:
970	kfree(kc);
971
972	return ERR_PTR(r);
973}
974EXPORT_SYMBOL(dm_kcopyd_client_create);
975
976void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc)
977{
978	/* Wait for completion of all jobs submitted by this client. */
979	wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs));
980
981	BUG_ON(!list_empty(&kc->callback_jobs));
982	BUG_ON(!list_empty(&kc->complete_jobs));
983	BUG_ON(!list_empty(&kc->io_jobs));
984	BUG_ON(!list_empty(&kc->pages_jobs));
985	destroy_workqueue(kc->kcopyd_wq);
986	dm_io_client_destroy(kc->io_client);
987	client_free_pages(kc);
988	mempool_exit(&kc->job_pool);
989	kfree(kc);
990}
991EXPORT_SYMBOL(dm_kcopyd_client_destroy);
992
993void dm_kcopyd_client_flush(struct dm_kcopyd_client *kc)
994{
995	flush_workqueue(kc->kcopyd_wq);
996}
997EXPORT_SYMBOL(dm_kcopyd_client_flush);
998