2 * Copyright (C) 2002 Sistina Software (UK) Limited.
3 * Copyright (C) 2006 Red Hat GmbH
5 * This file is released under the GPL.
7 * Kcopyd provides a simple interface for copying an area of one
8 * block-device to one or more other block-devices, with an asynchronous
9 * completion notification.
12 #include <linux/types.h>
13 #include <asm/atomic.h>
14 #include <linux/blkdev.h>
16 #include <linux/init.h>
17 #include <linux/list.h>
18 #include <linux/mempool.h>
19 #include <linux/module.h>
20 #include <linux/pagemap.h>
21 #include <linux/slab.h>
22 #include <linux/vmalloc.h>
23 #include <linux/workqueue.h>
24 #include <linux/mutex.h>
25 #include <linux/device-mapper.h>
26 #include <linux/dm-kcopyd.h>
30 #define SUB_JOB_SIZE 128
34 /*-----------------------------------------------------------------
35 * Each kcopyd client has its own little pool of preallocated
36 * pages for kcopyd io.
37 *---------------------------------------------------------------*/
38 struct dm_kcopyd_client {
40 struct page_list *pages;
41 unsigned int nr_pages;
42 unsigned int nr_free_pages;
44 struct dm_io_client *io_client;
46 wait_queue_head_t destroyq;
51 struct workqueue_struct *kcopyd_wq;
52 struct work_struct kcopyd_work;
55 * We maintain three lists of jobs:
57 * i) jobs waiting for pages
58 * ii) jobs that have pages, and are waiting for the io to be issued.
59 * iii) jobs that have completed.
61 * All three of these are protected by job_lock.
64 struct list_head complete_jobs;
65 struct list_head io_jobs;
66 struct list_head pages_jobs;
69 static void wake(struct dm_kcopyd_client *kc)
71 queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
74 static struct page_list *alloc_pl(void)
78 pl = kmalloc(sizeof(*pl), GFP_KERNEL);
82 pl->page = alloc_page(GFP_KERNEL);
91 static void free_pl(struct page_list *pl)
93 __free_page(pl->page);
97 static int kcopyd_get_pages(struct dm_kcopyd_client *kc,
98 unsigned int nr, struct page_list **pages)
100 struct page_list *pl;
102 spin_lock(&kc->lock);
103 if (kc->nr_free_pages < nr) {
104 spin_unlock(&kc->lock);
108 kc->nr_free_pages -= nr;
109 for (*pages = pl = kc->pages; --nr; pl = pl->next)
112 kc->pages = pl->next;
115 spin_unlock(&kc->lock);
120 static void kcopyd_put_pages(struct dm_kcopyd_client *kc, struct page_list *pl)
122 struct page_list *cursor;
124 spin_lock(&kc->lock);
125 for (cursor = pl; cursor->next; cursor = cursor->next)
129 cursor->next = kc->pages;
131 spin_unlock(&kc->lock);
135 * These three functions resize the page pool.
137 static void drop_pages(struct page_list *pl)
139 struct page_list *next;
148 static int client_alloc_pages(struct dm_kcopyd_client *kc, unsigned int nr)
151 struct page_list *pl = NULL, *next;
153 for (i = 0; i < nr; i++) {
164 kcopyd_put_pages(kc, pl);
169 static void client_free_pages(struct dm_kcopyd_client *kc)
171 BUG_ON(kc->nr_free_pages != kc->nr_pages);
172 drop_pages(kc->pages);
174 kc->nr_free_pages = kc->nr_pages = 0;
177 /*-----------------------------------------------------------------
178 * kcopyd_jobs need to be allocated by the *clients* of kcopyd,
179 * for this reason we use a mempool to prevent the client from
180 * ever having to do io (which could cause a deadlock).
181 *---------------------------------------------------------------*/
183 struct dm_kcopyd_client *kc;
184 struct list_head list;
188 * Error state of the job.
191 unsigned long write_err;
194 * Either READ or WRITE
197 struct dm_io_region source;
200 * The destinations for the transfer.
202 unsigned int num_dests;
203 struct dm_io_region dests[DM_KCOPYD_MAX_REGIONS];
206 unsigned int nr_pages;
207 struct page_list *pages;
210 * Set this to ensure you are notified when the job has
211 * completed. 'context' is for callback to use.
213 dm_kcopyd_notify_fn fn;
217 * These fields are only used if the job has been split
218 * into more manageable parts.
224 struct kcopyd_job *master_job;
227 static struct kmem_cache *_job_cache;
229 int __init dm_kcopyd_init(void)
231 _job_cache = kmem_cache_create("kcopyd_job",
232 sizeof(struct kcopyd_job) * (SPLIT_COUNT + 1),
233 __alignof__(struct kcopyd_job), 0, NULL);
240 void dm_kcopyd_exit(void)
242 kmem_cache_destroy(_job_cache);
247 * Functions to push and pop a job onto the head of a given job
250 static struct kcopyd_job *pop(struct list_head *jobs,
251 struct dm_kcopyd_client *kc)
253 struct kcopyd_job *job = NULL;
256 spin_lock_irqsave(&kc->job_lock, flags);
258 if (!list_empty(jobs)) {
259 job = list_entry(jobs->next, struct kcopyd_job, list);
260 list_del(&job->list);
262 spin_unlock_irqrestore(&kc->job_lock, flags);
267 static void push(struct list_head *jobs, struct kcopyd_job *job)
270 struct dm_kcopyd_client *kc = job->kc;
272 spin_lock_irqsave(&kc->job_lock, flags);
273 list_add_tail(&job->list, jobs);
274 spin_unlock_irqrestore(&kc->job_lock, flags);
278 static void push_head(struct list_head *jobs, struct kcopyd_job *job)
281 struct dm_kcopyd_client *kc = job->kc;
283 spin_lock_irqsave(&kc->job_lock, flags);
284 list_add(&job->list, jobs);
285 spin_unlock_irqrestore(&kc->job_lock, flags);
289 * These three functions process 1 item from the corresponding
295 * > 0: can't process yet.
297 static int run_complete_job(struct kcopyd_job *job)
299 void *context = job->context;
300 int read_err = job->read_err;
301 unsigned long write_err = job->write_err;
302 dm_kcopyd_notify_fn fn = job->fn;
303 struct dm_kcopyd_client *kc = job->kc;
306 kcopyd_put_pages(kc, job->pages);
308 * If this is the master job, the sub jobs have already
309 * completed so we can free everything.
311 if (job->master_job == job)
312 mempool_free(job, kc->job_pool);
313 fn(read_err, write_err, context);
315 if (atomic_dec_and_test(&kc->nr_jobs))
316 wake_up(&kc->destroyq);
321 static void complete_io(unsigned long error, void *context)
323 struct kcopyd_job *job = (struct kcopyd_job *) context;
324 struct dm_kcopyd_client *kc = job->kc;
327 if (job->rw == WRITE)
328 job->write_err |= error;
332 if (!test_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags)) {
333 push(&kc->complete_jobs, job);
339 if (job->rw == WRITE)
340 push(&kc->complete_jobs, job);
344 push(&kc->io_jobs, job);
351 * Request io on as many buffer heads as we can currently get for
354 static int run_io_job(struct kcopyd_job *job)
357 struct dm_io_request io_req = {
359 .mem.type = DM_IO_PAGE_LIST,
360 .mem.ptr.pl = job->pages,
361 .mem.offset = job->offset,
362 .notify.fn = complete_io,
363 .notify.context = job,
364 .client = job->kc->io_client,
368 r = dm_io(&io_req, 1, &job->source, NULL);
370 r = dm_io(&io_req, job->num_dests, job->dests, NULL);
375 static int run_pages_job(struct kcopyd_job *job)
379 job->nr_pages = dm_div_up(job->dests[0].count + job->offset,
381 r = kcopyd_get_pages(job->kc, job->nr_pages, &job->pages);
383 /* this job is ready for io */
384 push(&job->kc->io_jobs, job);
389 /* can't complete now */
396 * Run through a list for as long as possible. Returns the count
397 * of successful jobs.
399 static int process_jobs(struct list_head *jobs, struct dm_kcopyd_client *kc,
400 int (*fn) (struct kcopyd_job *))
402 struct kcopyd_job *job;
405 while ((job = pop(jobs, kc))) {
410 /* error this rogue job */
411 if (job->rw == WRITE)
412 job->write_err = (unsigned long) -1L;
415 push(&kc->complete_jobs, job);
421 * We couldn't service this job ATM, so
422 * push this job back onto the list.
424 push_head(jobs, job);
435 * kcopyd does this every time it's woken up.
437 static void do_work(struct work_struct *work)
439 struct dm_kcopyd_client *kc = container_of(work,
440 struct dm_kcopyd_client, kcopyd_work);
441 struct blk_plug plug;
444 * The order that these are called is *very* important.
445 * complete jobs can free some pages for pages jobs.
446 * Pages jobs when successful will jump onto the io jobs
447 * list. io jobs call wake when they complete and it all
450 blk_start_plug(&plug);
451 process_jobs(&kc->complete_jobs, kc, run_complete_job);
452 process_jobs(&kc->pages_jobs, kc, run_pages_job);
453 process_jobs(&kc->io_jobs, kc, run_io_job);
454 blk_finish_plug(&plug);
458 * If we are copying a small region we just dispatch a single job
459 * to do the copy, otherwise the io has to be split up into many
462 static void dispatch_job(struct kcopyd_job *job)
464 struct dm_kcopyd_client *kc = job->kc;
465 atomic_inc(&kc->nr_jobs);
466 if (unlikely(!job->source.count))
467 push(&kc->complete_jobs, job);
469 push(&kc->pages_jobs, job);
473 static void segment_complete(int read_err, unsigned long write_err,
476 /* FIXME: tidy this function */
477 sector_t progress = 0;
479 struct kcopyd_job *sub_job = (struct kcopyd_job *) context;
480 struct kcopyd_job *job = sub_job->master_job;
481 struct dm_kcopyd_client *kc = job->kc;
483 mutex_lock(&job->lock);
485 /* update the error */
490 job->write_err |= write_err;
493 * Only dispatch more work if there hasn't been an error.
495 if ((!job->read_err && !job->write_err) ||
496 test_bit(DM_KCOPYD_IGNORE_ERROR, &job->flags)) {
497 /* get the next chunk of work */
498 progress = job->progress;
499 count = job->source.count - progress;
501 if (count > SUB_JOB_SIZE)
502 count = SUB_JOB_SIZE;
504 job->progress += count;
507 mutex_unlock(&job->lock);
513 sub_job->source.sector += progress;
514 sub_job->source.count = count;
516 for (i = 0; i < job->num_dests; i++) {
517 sub_job->dests[i].sector += progress;
518 sub_job->dests[i].count = count;
521 sub_job->fn = segment_complete;
522 sub_job->context = sub_job;
523 dispatch_job(sub_job);
525 } else if (atomic_dec_and_test(&job->sub_jobs)) {
528 * Queue the completion callback to the kcopyd thread.
530 * Some callers assume that all the completions are called
531 * from a single thread and don't race with each other.
533 * We must not call the callback directly here because this
534 * code may not be executing in the thread.
536 push(&kc->complete_jobs, job);
542 * Create some sub jobs to share the work between them.
544 static void split_job(struct kcopyd_job *master_job)
548 atomic_inc(&master_job->kc->nr_jobs);
550 atomic_set(&master_job->sub_jobs, SPLIT_COUNT);
551 for (i = 0; i < SPLIT_COUNT; i++) {
552 master_job[i + 1].master_job = master_job;
553 segment_complete(0, 0u, &master_job[i + 1]);
557 int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
558 unsigned int num_dests, struct dm_io_region *dests,
559 unsigned int flags, dm_kcopyd_notify_fn fn, void *context)
561 struct kcopyd_job *job;
564 * Allocate an array of jobs consisting of one master job
565 * followed by SPLIT_COUNT sub jobs.
567 job = mempool_alloc(kc->job_pool, GFP_NOIO);
570 * set up for the read.
580 job->num_dests = num_dests;
581 memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
588 job->context = context;
589 job->master_job = job;
591 if (job->source.count <= SUB_JOB_SIZE)
594 mutex_init(&job->lock);
601 EXPORT_SYMBOL(dm_kcopyd_copy);
604 * Cancels a kcopyd job, eg. someone might be deactivating a
608 int kcopyd_cancel(struct kcopyd_job *job, int block)
615 /*-----------------------------------------------------------------
617 *---------------------------------------------------------------*/
618 int dm_kcopyd_client_create(unsigned int nr_pages,
619 struct dm_kcopyd_client **result)
622 struct dm_kcopyd_client *kc;
624 kc = kmalloc(sizeof(*kc), GFP_KERNEL);
628 spin_lock_init(&kc->lock);
629 spin_lock_init(&kc->job_lock);
630 INIT_LIST_HEAD(&kc->complete_jobs);
631 INIT_LIST_HEAD(&kc->io_jobs);
632 INIT_LIST_HEAD(&kc->pages_jobs);
634 kc->job_pool = mempool_create_slab_pool(MIN_JOBS, _job_cache);
638 INIT_WORK(&kc->kcopyd_work, do_work);
639 kc->kcopyd_wq = alloc_workqueue("kcopyd",
640 WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
645 kc->nr_pages = kc->nr_free_pages = 0;
646 r = client_alloc_pages(kc, nr_pages);
648 goto bad_client_pages;
650 kc->io_client = dm_io_client_create(nr_pages);
651 if (IS_ERR(kc->io_client)) {
652 r = PTR_ERR(kc->io_client);
656 init_waitqueue_head(&kc->destroyq);
657 atomic_set(&kc->nr_jobs, 0);
663 client_free_pages(kc);
665 destroy_workqueue(kc->kcopyd_wq);
667 mempool_destroy(kc->job_pool);
673 EXPORT_SYMBOL(dm_kcopyd_client_create);
675 void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc)
677 /* Wait for completion of all jobs submitted by this client. */
678 wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs));
680 BUG_ON(!list_empty(&kc->complete_jobs));
681 BUG_ON(!list_empty(&kc->io_jobs));
682 BUG_ON(!list_empty(&kc->pages_jobs));
683 destroy_workqueue(kc->kcopyd_wq);
684 dm_io_client_destroy(kc->io_client);
685 client_free_pages(kc);
686 mempool_destroy(kc->job_pool);
689 EXPORT_SYMBOL(dm_kcopyd_client_destroy);