/* * Copyright (C) 2002 Sistina Software (UK) Limited. * Copyright (C) 2006 Red Hat GmbH * * This file is released under the GPL. * * Kcopyd provides a simple interface for copying an area of one * block-device to one or more other block-devices, with an asynchronous * completion notification. */ #include <asm/types.h> #include <asm/atomic.h> #include <linux/blkdev.h> #include <linux/fs.h> #include <linux/init.h> #include <linux/list.h> #include <linux/mempool.h> #include <linux/module.h> #include <linux/pagemap.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/workqueue.h> #include <linux/mutex.h> #include "kcopyd.h" static struct workqueue_struct *_kcopyd_wq; static struct work_struct _kcopyd_work; static void wake(void) { queue_work(_kcopyd_wq, &_kcopyd_work); } /*----------------------------------------------------------------- * Each kcopyd client has its own little pool of preallocated * pages for kcopyd io. *---------------------------------------------------------------*/ struct kcopyd_client { struct list_head list; spinlock_t lock; struct page_list *pages; unsigned int nr_pages; unsigned int nr_free_pages; struct dm_io_client *io_client; wait_queue_head_t destroyq; atomic_t nr_jobs; }; static struct page_list *alloc_pl(void) { struct page_list *pl; pl = kmalloc(sizeof(*pl), GFP_KERNEL); if (!pl) return NULL; pl->page = alloc_page(GFP_KERNEL); if (!pl->page) { kfree(pl); return NULL; } return pl; } static void free_pl(struct page_list *pl) { __free_page(pl->page); kfree(pl); } static int kcopyd_get_pages(struct kcopyd_client *kc, unsigned int nr, struct page_list **pages) { struct page_list *pl; spin_lock(&kc->lock); if (kc->nr_free_pages < nr) { spin_unlock(&kc->lock); return -ENOMEM; } kc->nr_free_pages -= nr; for (*pages = pl = kc->pages; --nr; pl = pl->next) ; kc->pages = pl->next; pl->next = NULL; spin_unlock(&kc->lock); return 0; } static void kcopyd_put_pages(struct kcopyd_client *kc, struct page_list *pl) { struct page_list *cursor; spin_lock(&kc->lock); for (cursor = pl; cursor->next; cursor = cursor->next) kc->nr_free_pages++; kc->nr_free_pages++; cursor->next = kc->pages; kc->pages = pl; spin_unlock(&kc->lock); } /* * These three functions resize the page pool. */ static void drop_pages(struct page_list *pl) { struct page_list *next; while (pl) { next = pl->next; free_pl(pl); pl = next; } } static int client_alloc_pages(struct kcopyd_client *kc, unsigned int nr) { unsigned int i; struct page_list *pl = NULL, *next; for (i = 0; i < nr; i++) { next = alloc_pl(); if (!next) { if (pl) drop_pages(pl); return -ENOMEM; } next->next = pl; pl = next; } kcopyd_put_pages(kc, pl); kc->nr_pages += nr; return 0; } static void client_free_pages(struct kcopyd_client *kc) { BUG_ON(kc->nr_free_pages != kc->nr_pages); drop_pages(kc->pages); kc->pages = NULL; kc->nr_free_pages = kc->nr_pages = 0; } /*----------------------------------------------------------------- * kcopyd_jobs need to be allocated by the *clients* of kcopyd, * for this reason we use a mempool to prevent the client from * ever having to do io (which could cause a deadlock). *---------------------------------------------------------------*/ struct kcopyd_job { struct kcopyd_client *kc; struct list_head list; unsigned long flags; /* * Error state of the job. */ int read_err; unsigned int write_err; /* * Either READ or WRITE */ int rw; struct io_region source; /* * The destinations for the transfer. */ unsigned int num_dests; struct io_region dests[KCOPYD_MAX_REGIONS]; sector_t offset; unsigned int nr_pages; struct page_list *pages; /* * Set this to ensure you are notified when the job has * completed. 'context' is for callback to use. */ kcopyd_notify_fn fn; void *context; /* * These fields are only used if the job has been split * into more manageable parts. */ struct mutex lock; atomic_t sub_jobs; sector_t progress; }; /* FIXME: this should scale with the number of pages */ #define MIN_JOBS 512 static struct kmem_cache *_job_cache; static mempool_t *_job_pool; /* * We maintain three lists of jobs: * * i) jobs waiting for pages * ii) jobs that have pages, and are waiting for the io to be issued. * iii) jobs that have completed. * * All three of these are protected by job_lock. */ static DEFINE_SPINLOCK(_job_lock); static LIST_HEAD(_complete_jobs); static LIST_HEAD(_io_jobs); static LIST_HEAD(_pages_jobs); static int jobs_init(void) { _job_cache = KMEM_CACHE(kcopyd_job, 0); if (!_job_cache) return -ENOMEM; _job_pool = mempool_create_slab_pool(MIN_JOBS, _job_cache); if (!_job_pool) { kmem_cache_destroy(_job_cache); return -ENOMEM; } return 0; } static void jobs_exit(void) { BUG_ON(!list_empty(&_complete_jobs)); BUG_ON(!list_empty(&_io_jobs)); BUG_ON(!list_empty(&_pages_jobs)); mempool_destroy(_job_pool); kmem_cache_destroy(_job_cache); _job_pool = NULL; _job_cache = NULL; } /* * Functions to push and pop a job onto the head of a given job * list. */ static struct kcopyd_job *pop(struct list_head *jobs) { struct kcopyd_job *job = NULL; unsigned long flags; spin_lock_irqsave(&_job_lock, flags); if (!list_empty(jobs)) { job = list_entry(jobs->next, struct kcopyd_job, list); list_del(&job->list); } spin_unlock_irqrestore(&_job_lock, flags); return job; } static void push(struct list_head *jobs, struct kcopyd_job *job) { unsigned long flags; spin_lock_irqsave(&_job_lock, flags); list_add_tail(&job->list, jobs); spin_unlock_irqrestore(&_job_lock, flags); } /* * These three functions process 1 item from the corresponding * job list. * * They return: * < 0: error * 0: success * > 0: can't process yet. */ static int run_complete_job(struct kcopyd_job *job) { void *context = job->context; int read_err = job->read_err; unsigned int write_err = job->write_err; kcopyd_notify_fn fn = job->fn; struct kcopyd_client *kc = job->kc; kcopyd_put_pages(kc, job->pages); mempool_free(job, _job_pool); fn(read_err, write_err, context); if (atomic_dec_and_test(&kc->nr_jobs)) wake_up(&kc->destroyq); return 0; } static void complete_io(unsigned long error, void *context) { struct kcopyd_job *job = (struct kcopyd_job *) context; if (error) { if (job->rw == WRITE) job->write_err |= error; else job->read_err = 1; if (!test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) { push(&_complete_jobs, job); wake(); return; } } if (job->rw == WRITE) push(&_complete_jobs, job); else { job->rw = WRITE; push(&_io_jobs, job); } wake(); } /* * Request io on as many buffer heads as we can currently get for * a particular job. */ static int run_io_job(struct kcopyd_job *job) { int r; struct dm_io_request io_req = { .bi_rw = job->rw, .mem.type = DM_IO_PAGE_LIST, .mem.ptr.pl = job->pages, .mem.offset = job->offset, .notify.fn = complete_io, .notify.context = job, .client = job->kc->io_client, }; if (job->rw == READ) r = dm_io(&io_req, 1, &job->source, NULL); else r = dm_io(&io_req, job->num_dests, job->dests, NULL); return r; } static int run_pages_job(struct kcopyd_job *job) { int r; job->nr_pages = dm_div_up(job->dests[0].count + job->offset, PAGE_SIZE >> 9); r = kcopyd_get_pages(job->kc, job->nr_pages, &job->pages); if (!r) { /* this job is ready for io */ push(&_io_jobs, job); return 0; } if (r == -ENOMEM) /* can't complete now */ return 1; return r; } /* * Run through a list for as long as possible. Returns the count * of successful jobs. */ static int process_jobs(struct list_head *jobs, int (*fn) (struct kcopyd_job *)) { struct kcopyd_job *job; int r, count = 0; while ((job = pop(jobs))) { r = fn(job); if (r < 0) { /* error this rogue job */ if (job->rw == WRITE) job->write_err = (unsigned int) -1; else job->read_err = 1; push(&_complete_jobs, job); break; } if (r > 0) { /* * We couldn't service this job ATM, so * push this job back onto the list. */ push(jobs, job); break; } count++; } return count; } /* * kcopyd does this every time it's woken up. */ static void do_work(struct work_struct *ignored) { /* * The order that these are called is *very* important. * complete jobs can free some pages for pages jobs. * Pages jobs when successful will jump onto the io jobs * list. io jobs call wake when they complete and it all * starts again. */ process_jobs(&_complete_jobs, run_complete_job); process_jobs(&_pages_jobs, run_pages_job); process_jobs(&_io_jobs, run_io_job); } /* * If we are copying a small region we just dispatch a single job * to do the copy, otherwise the io has to be split up into many * jobs. */ static void dispatch_job(struct kcopyd_job *job) { atomic_inc(&job->kc->nr_jobs); push(&_pages_jobs, job); wake(); } #define SUB_JOB_SIZE 128 static void segment_complete(int read_err, unsigned int write_err, void *context) { /* FIXME: tidy this function */ sector_t progress = 0; sector_t count = 0; struct kcopyd_job *job = (struct kcopyd_job *) context; mutex_lock(&job->lock); /* update the error */ if (read_err) job->read_err = 1; if (write_err) job->write_err |= write_err; /* * Only dispatch more work if there hasn't been an error. */ if ((!job->read_err && !job->write_err) || test_bit(KCOPYD_IGNORE_ERROR, &job->flags)) { /* get the next chunk of work */ progress = job->progress; count = job->source.count - progress; if (count) { if (count > SUB_JOB_SIZE) count = SUB_JOB_SIZE; job->progress += count; } } mutex_unlock(&job->lock); if (count) { int i; struct kcopyd_job *sub_job = mempool_alloc(_job_pool, GFP_NOIO); *sub_job = *job; sub_job->source.sector += progress; sub_job->source.count = count; for (i = 0; i < job->num_dests; i++) { sub_job->dests[i].sector += progress; sub_job->dests[i].count = count; } sub_job->fn = segment_complete; sub_job->context = job; dispatch_job(sub_job); } else if (atomic_dec_and_test(&job->sub_jobs)) { /* * To avoid a race we must keep the job around * until after the notify function has completed. * Otherwise the client may try and stop the job * after we've completed. */ job->fn(read_err, write_err, job->context); mempool_free(job, _job_pool); } } /* * Create some little jobs that will do the move between * them. */ #define SPLIT_COUNT 8 static void split_job(struct kcopyd_job *job) { int i; atomic_set(&job->sub_jobs, SPLIT_COUNT); for (i = 0; i < SPLIT_COUNT; i++) segment_complete(0, 0u, job); } int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from, unsigned int num_dests, struct io_region *dests, unsigned int flags, kcopyd_notify_fn fn, void *context) { struct kcopyd_job *job; /* * Allocate a new job. */ job = mempool_alloc(_job_pool, GFP_NOIO); /* * set up for the read. */ job->kc = kc; job->flags = flags; job->read_err = 0; job->write_err = 0; job->rw = READ; job->source = *from; job->num_dests = num_dests; memcpy(&job->dests, dests, sizeof(*dests) * num_dests); job->offset = 0; job->nr_pages = 0; job->pages = NULL; job->fn = fn; job->context = context; if (job->source.count < SUB_JOB_SIZE) dispatch_job(job); else { mutex_init(&job->lock); job->progress = 0; split_job(job); } return 0; } /* * Cancels a kcopyd job, eg. someone might be deactivating a * mirror. */ #if 0 int kcopyd_cancel(struct kcopyd_job *job, int block) { /* FIXME: finish */ return -1; } #endif /* 0 */ /*----------------------------------------------------------------- * Unit setup *---------------------------------------------------------------*/ static DEFINE_MUTEX(_client_lock); static LIST_HEAD(_clients); static void client_add(struct kcopyd_client *kc) { mutex_lock(&_client_lock); list_add(&kc->list, &_clients); mutex_unlock(&_client_lock); } static void client_del(struct kcopyd_client *kc) { mutex_lock(&_client_lock); list_del(&kc->list); mutex_unlock(&_client_lock); } static DEFINE_MUTEX(kcopyd_init_lock); static int kcopyd_clients = 0; static int kcopyd_init(void) { int r; mutex_lock(&kcopyd_init_lock); if (kcopyd_clients) { /* Already initialized. */ kcopyd_clients++; mutex_unlock(&kcopyd_init_lock); return 0; } r = jobs_init(); if (r) { mutex_unlock(&kcopyd_init_lock); return r; } _kcopyd_wq = create_singlethread_workqueue("kcopyd"); if (!_kcopyd_wq) { jobs_exit(); mutex_unlock(&kcopyd_init_lock); return -ENOMEM; } kcopyd_clients++; INIT_WORK(&_kcopyd_work, do_work); mutex_unlock(&kcopyd_init_lock); return 0; } static void kcopyd_exit(void) { mutex_lock(&kcopyd_init_lock); kcopyd_clients--; if (!kcopyd_clients) { jobs_exit(); destroy_workqueue(_kcopyd_wq); _kcopyd_wq = NULL; } mutex_unlock(&kcopyd_init_lock); } int kcopyd_client_create(unsigned int nr_pages, struct kcopyd_client **result) { int r = 0; struct kcopyd_client *kc; r = kcopyd_init(); if (r) return r; kc = kmalloc(sizeof(*kc), GFP_KERNEL); if (!kc) { kcopyd_exit(); return -ENOMEM; } spin_lock_init(&kc->lock); kc->pages = NULL; kc->nr_pages = kc->nr_free_pages = 0; r = client_alloc_pages(kc, nr_pages); if (r) { kfree(kc); kcopyd_exit(); return r; } kc->io_client = dm_io_client_create(nr_pages); if (IS_ERR(kc->io_client)) { r = PTR_ERR(kc->io_client); client_free_pages(kc); kfree(kc); kcopyd_exit(); return r; } init_waitqueue_head(&kc->destroyq); atomic_set(&kc->nr_jobs, 0); client_add(kc); *result = kc; return 0; } void kcopyd_client_destroy(struct kcopyd_client *kc) { /* Wait for completion of all jobs submitted by this client. */ wait_event(kc->destroyq, !atomic_read(&kc->nr_jobs)); dm_io_client_destroy(kc->io_client); client_free_pages(kc); client_del(kc); kfree(kc); kcopyd_exit(); } EXPORT_SYMBOL(kcopyd_client_create); EXPORT_SYMBOL(kcopyd_client_destroy); EXPORT_SYMBOL(kcopyd_copy);