1 files changed, 687 insertions, 0 deletions

diff --git a/drivers/md/kcopyd.c b/drivers/md/kcopyd.c
new file mode 100644
index 000000000000..eb7036485975
--- /dev/null
+++ b/drivers/md/kcopyd.c
@@ -0,0 +1,687 @@
+/*
+ * Copyright (C) 2002 Sistina Software (UK) Limited.
+ *
+ * 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/atomic.h>
+
+#include <linux/blkdev.h>
+#include <linux/config.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 "kcopyd.h"
+
+static struct workqueue_struct *_kcopyd_wq;
+static struct work_struct _kcopyd_work;
+
+static inline 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;
+};
+
+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 semaphore lock;
+        atomic_t sub_jobs;
+        sector_t progress;
+};
+
+/* FIXME: this should scale with the number of pages */
+#define MIN_JOBS 512
+
+static kmem_cache_t *_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_create("kcopyd-jobs",
+                                       sizeof(struct kcopyd_job),
+                                       __alignof__(struct kcopyd_job),
+                                       0, NULL, NULL);
+        if (!_job_cache)
+                return -ENOMEM;
+
+        _job_pool = mempool_create(MIN_JOBS, mempool_alloc_slab,
+                                   mempool_free_slab, _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 inline 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 inline 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;
+
+        kcopyd_put_pages(job->kc, job->pages);
+        mempool_free(job, _job_pool);
+        fn(read_err, write_err, context);
+        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;
+
+        if (job->rw == READ)
+                r = dm_io_async(1, &job->source, job->rw,
+                                job->pages,
+                                job->offset, complete_io, job);
+
+        else
+                r = dm_io_async(job->num_dests, job->dests, job->rw,
+                                job->pages,
+                                job->offset, complete_io, job);
+
+        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(void *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)
+{
+        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;
+
+        down(&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;
+                }
+        }
+        up(&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 {
+                init_MUTEX(&job->lock);
+                job->progress = 0;
+                split_job(job);
+        }
+
+        return 0;
+}
+
+/*
+ * Cancels a kcopyd job, eg. someone might be deactivating a
+ * mirror.
+ */
+int kcopyd_cancel(struct kcopyd_job *job, int block)
+{
+        /* FIXME: finish */
+        return -1;
+}
+
+/*-----------------------------------------------------------------
+ * Unit setup
+ *---------------------------------------------------------------*/
+static DECLARE_MUTEX(_client_lock);
+static LIST_HEAD(_clients);
+
+static void client_add(struct kcopyd_client *kc)
+{
+        down(&_client_lock);
+        list_add(&kc->list, &_clients);
+        up(&_client_lock);
+}
+
+static void client_del(struct kcopyd_client *kc)
+{
+        down(&_client_lock);
+        list_del(&kc->list);
+        up(&_client_lock);
+}
+
+static DECLARE_MUTEX(kcopyd_init_lock);
+static int kcopyd_clients = 0;
+
+static int kcopyd_init(void)
+{
+        int r;
+
+        down(&kcopyd_init_lock);
+
+        if (kcopyd_clients) {
+                /* Already initialized. */
+                kcopyd_clients++;
+                up(&kcopyd_init_lock);
+                return 0;
+        }
+
+        r = jobs_init();
+        if (r) {
+                up(&kcopyd_init_lock);
+                return r;
+        }
+
+        _kcopyd_wq = create_singlethread_workqueue("kcopyd");
+        if (!_kcopyd_wq) {
+                jobs_exit();
+                up(&kcopyd_init_lock);
+                return -ENOMEM;
+        }
+
+        kcopyd_clients++;
+        INIT_WORK(&_kcopyd_work, do_work, NULL);
+        up(&kcopyd_init_lock);
+        return 0;
+}
+
+static void kcopyd_exit(void)
+{
+        down(&kcopyd_init_lock);
+        kcopyd_clients--;
+        if (!kcopyd_clients) {
+                jobs_exit();
+                destroy_workqueue(_kcopyd_wq);
+                _kcopyd_wq = NULL;
+        }
+        up(&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;
+        }
+
+        r = dm_io_get(nr_pages);
+        if (r) {
+                client_free_pages(kc);
+                kfree(kc);
+                kcopyd_exit();
+                return r;
+        }
+
+        client_add(kc);
+        *result = kc;
+        return 0;
+}
+
+void kcopyd_client_destroy(struct kcopyd_client *kc)
+{
+        dm_io_put(kc->nr_pages);
+        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);
+EXPORT_SYMBOL(kcopyd_cancel);