/*
 * bcache journalling code, for btree insertions
 *
 * Copyright 2012 Google, Inc.
 */

#include "bcache.h"
#include "btree.h"
#include "debug.h"
#include "request.h"

/*
 * Journal replay/recovery:
 *
 * This code is all driven from run_cache_set(); we first read the journal
 * entries, do some other stuff, then we mark all the keys in the journal
 * entries (same as garbage collection would), then we replay them - reinserting
 * them into the cache in precisely the same order as they appear in the
 * journal.
 *
 * We only journal keys that go in leaf nodes, which simplifies things quite a
 * bit.
 */

static void journal_read_endio(struct bio *bio, int error)
{
        struct closure *cl = bio->bi_private;
        closure_put(cl);
}

static int journal_read_bucket(struct cache *ca, struct list_head *list,
                               struct btree_op *op, unsigned bucket_index)
{
        struct journal_device *ja = &ca->journal;
        struct bio *bio = &ja->bio;

        struct journal_replay *i;
        struct jset *j, *data = ca->set->journal.w[0].data;
        unsigned len, left, offset = 0;
        int ret = 0;
        sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);

        pr_debug("reading %llu", (uint64_t) bucket);

        while (offset < ca->sb.bucket_size) {
reread:         left = ca->sb.bucket_size - offset;
                len = min_t(unsigned, left, PAGE_SECTORS * 8);

                bio_reset(bio);
                bio->bi_sector  = bucket + offset;
                bio->bi_bdev    = ca->bdev;
                bio->bi_rw      = READ;
                bio->bi_size    = len << 9;

                bio->bi_end_io  = journal_read_endio;
                bio->bi_private = &op->cl;
                bch_bio_map(bio, data);

                closure_bio_submit(bio, &op->cl, ca);
                closure_sync(&op->cl);

                /* This function could be simpler now since we no longer write
                 * journal entries that overlap bucket boundaries; this means
                 * the start of a bucket will always have a valid journal entry
                 * if it has any journal entries at all.
                 */

                j = data;
                while (len) {
                        struct list_head *where;
                        size_t blocks, bytes = set_bytes(j);

                        if (j->magic != jset_magic(ca->set))
                                return ret;

                        if (bytes > left << 9)
                                return ret;

                        if (bytes > len << 9)
                                goto reread;

                        if (j->csum != csum_set(j))
                                return ret;

                        blocks = set_blocks(j, ca->set);

                        while (!list_empty(list)) {
                                i = list_first_entry(list,
                                        struct journal_replay, list);
                                if (i->j.seq >= j->last_seq)
                                        break;
                                list_del(&i->list);
                                kfree(i);
                        }

                        list_for_each_entry_reverse(i, list, list) {
                                if (j->seq == i->j.seq)
                                        goto next_set;

                                if (j->seq < i->j.last_seq)
                                        goto next_set;

                                if (j->seq > i->j.seq) {
                                        where = &i->list;
                                        goto add;
                                }
                        }

                        where = list;
add:
                        i = kmalloc(offsetof(struct journal_replay, j) +
                                    bytes, GFP_KERNEL);
                        if (!i)
                                return -ENOMEM;
                        memcpy(&i->j, j, bytes);
                        list_add(&i->list, where);
                        ret = 1;

                        ja->seq[bucket_index] = j->seq;
next_set:
                        offset  += blocks * ca->sb.block_size;
                        len     -= blocks * ca->sb.block_size;
                        j = ((void *) j) + blocks * block_bytes(ca);
                }
        }

        return ret;
}

int bch_journal_read(struct cache_set *c, struct list_head *list,
                        struct btree_op *op)
{
#define read_bucket(b)                                                  \
        ({                                                              \
                int ret = journal_read_bucket(ca, list, op, b);         \
                __set_bit(b, bitmap);                                   \
                if (ret < 0)                                            \
                        return ret;                                     \
                ret;                                                    \
        })

        struct cache *ca;
        unsigned iter;

        for_each_cache(ca, c, iter) {
                struct journal_device *ja = &ca->journal;
                unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
                unsigned i, l, r, m;
                uint64_t seq;

                bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
                pr_debug("%u journal buckets", ca->sb.njournal_buckets);

                /* Read journal buckets ordered by golden ratio hash to quickly
                 * find a sequence of buckets with valid journal entries
                 */
                for (i = 0; i < ca->sb.njournal_buckets; i++) {
                        l = (i * 2654435769U) % ca->sb.njournal_buckets;

                        if (test_bit(l, bitmap))
                                break;

                        if (read_bucket(l))
                                goto bsearch;
                }

                /* If that fails, check all the buckets we haven't checked
                 * already
                 */
                pr_debug("falling back to linear search");

                for (l = 0; l < ca->sb.njournal_buckets; l++) {
                        if (test_bit(l, bitmap))
                                continue;

                        if (read_bucket(l))
                                goto bsearch;
                }
bsearch:
                /* Binary search */
                m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
                pr_debug("starting binary search, l %u r %u", l, r);

                while (l + 1 < r) {
                        m = (l + r) >> 1;

                        if (read_bucket(m))
                                l = m;
                        else
                                r = m;
                }

                /* Read buckets in reverse order until we stop finding more
                 * journal entries
                 */
                pr_debug("finishing up");
                l = m;

                while (1) {
                        if (!l--)
                                l = ca->sb.njournal_buckets - 1;

                        if (l == m)
                                break;

                        if (test_bit(l, bitmap))
                                continue;

                        if (!read_bucket(l))
                                break;
                }

                seq = 0;

                for (i = 0; i < ca->sb.njournal_buckets; i++)
                        if (ja->seq[i] > seq) {
                                seq = ja->seq[i];
                                ja->cur_idx = ja->discard_idx =
                                        ja->last_idx = i;

                        }
        }

        c->journal.seq = list_entry(list->prev,
                                    struct journal_replay,
                                    list)->j.seq;

        return 0;
#undef read_bucket
}

void bch_journal_mark(struct cache_set *c, struct list_head *list)
{
        atomic_t p = { 0 };
        struct bkey *k;
        struct journal_replay *i;
        struct journal *j = &c->journal;
        uint64_t last = j->seq;

        /*
         * journal.pin should never fill up - we never write a journal
         * entry when it would fill up. But if for some reason it does, we
         * iterate over the list in reverse order so that we can just skip that
         * refcount instead of bugging.
         */

        list_for_each_entry_reverse(i, list, list) {
                BUG_ON(last < i->j.seq);
                i->pin = NULL;

                while (last-- != i->j.seq)
                        if (fifo_free(&j->pin) > 1) {
                                fifo_push_front(&j->pin, p);
                                atomic_set(&fifo_front(&j->pin), 0);
                        }

                if (fifo_free(&j->pin) > 1) {
                        fifo_push_front(&j->pin, p);
                        i->pin = &fifo_front(&j->pin);
                        atomic_set(i->pin, 1);
                }

                for (k = i->j.start;
                     k < end(&i->j);
                     k = bkey_next(k)) {
                        unsigned j;

                        for (j = 0; j < KEY_PTRS(k); j++) {
                                struct bucket *g = PTR_BUCKET(c, k, j);
                                atomic_inc(&g->pin);

                                if (g->prio == BTREE_PRIO &&
                                    !ptr_stale(c, k, j))
                                        g->prio = INITIAL_PRIO;
                        }

                        __bch_btree_mark_key(c, 0, k);
                }
        }
}

int bch_journal_replay(struct cache_set *s, struct list_head *list,
                          struct btree_op *op)
{
        int ret = 0, keys = 0, entries = 0;
        struct bkey *k;
        struct journal_replay *i =
                list_entry(list->prev, struct journal_replay, list);

        uint64_t start = i->j.last_seq, end = i->j.seq, n = start;

        list_for_each_entry(i, list, list) {
                BUG_ON(i->pin && atomic_read(i->pin) != 1);

                if (n != i->j.seq)
                        pr_err(
                "journal entries %llu-%llu missing! (replaying %llu-%llu)\n",
                n, i->j.seq - 1, start, end);

                for (k = i->j.start;
                     k < end(&i->j);
                     k = bkey_next(k)) {
                        pr_debug("%s", pkey(k));
                        bkey_copy(op->keys.top, k);
                        bch_keylist_push(&op->keys);

                        op->journal = i->pin;
                        atomic_inc(op->journal);

                        ret = bch_btree_insert(op, s);
                        if (ret)
                                goto err;

                        BUG_ON(!bch_keylist_empty(&op->keys));
                        keys++;

                        cond_resched();
                }

                if (i->pin)
                        atomic_dec(i->pin);
                n = i->j.seq + 1;
                entries++;
        }

        pr_info("journal replay done, %i keys in %i entries, seq %llu",
                keys, entries, end);

        while (!list_empty(list)) {
                i = list_first_entry(list, struct journal_replay, list);
                list_del(&i->list);
                kfree(i);
        }
err:
        closure_sync(&op->cl);
        return ret;
}

/* Journalling */

static void btree_flush_write(struct cache_set *c)
{
        /*
         * Try to find the btree node with that references the oldest journal
         * entry, best is our current candidate and is locked if non NULL:
         */
        struct btree *b, *best = NULL;
        unsigned iter;

        for_each_cached_btree(b, c, iter) {
                if (!down_write_trylock(&b->lock))
                        continue;

                if (!btree_node_dirty(b) ||
                    !btree_current_write(b)->journal) {
                        rw_unlock(true, b);
                        continue;
                }

                if (!best)
                        best = b;
                else if (journal_pin_cmp(c,
                                         btree_current_write(best),
                                         btree_current_write(b))) {
                        rw_unlock(true, best);
                        best = b;
                } else
                        rw_unlock(true, b);
        }

        if (best)
                goto out;

        /* We can't find the best btree node, just pick the first */
        list_for_each_entry(b, &c->btree_cache, list)
                if (!b->level && btree_node_dirty(b)) {
                        best = b;
                        rw_lock(true, best, best->level);
                        goto found;
                }

out:
        if (!best)
                return;
found:
        if (btree_node_dirty(best))
                bch_btree_write(best, true, NULL);
        rw_unlock(true, best);
}

#define last_seq(j)     ((j)->seq - fifo_used(&(j)->pin) + 1)

static void journal_discard_endio(struct bio *bio, int error)
{
        struct journal_device *ja =
                container_of(bio, struct journal_device, discard_bio);
        struct cache *ca = container_of(ja, struct cache, journal);

        atomic_set(&ja->discard_in_flight, DISCARD_DONE);

        closure_wake_up(&ca->set->journal.wait);
        closure_put(&ca->set->cl);
}

static void journal_discard_work(struct work_struct *work)
{
        struct journal_device *ja =
                container_of(work, struct journal_device, discard_work);

        submit_bio(0, &ja->discard_bio);
}

static void do_journal_discard(struct cache *ca)
{
        struct journal_device *ja = &ca->journal;
        struct bio *bio = &ja->discard_bio;

        if (!ca->discard) {
                ja->discard_idx = ja->last_idx;
                return;
        }

        switch (atomic_read(&ja->discard_in_flight) == DISCARD_IN_FLIGHT) {
        case DISCARD_IN_FLIGHT:
                return;

        case DISCARD_DONE:
                ja->discard_idx = (ja->discard_idx + 1) %
                        ca->sb.njournal_buckets;

                atomic_set(&ja->discard_in_flight, DISCARD_READY);
                /* fallthrough */

        case DISCARD_READY:
                if (ja->discard_idx == ja->last_idx)
                        return;

                atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);

                bio_init(bio);
                bio->bi_sector          = bucket_to_sector(ca->set,
                                                ca->sb.d[ja->discard_idx]);
                bio->bi_bdev            = ca->bdev;
                bio->bi_rw              = REQ_WRITE|REQ_DISCARD;
                bio->bi_max_vecs        = 1;
                bio->bi_io_vec          = bio->bi_inline_vecs;
                bio->bi_size            = bucket_bytes(ca);
                bio->bi_end_io          = journal_discard_endio;

                closure_get(&ca->set->cl);
                INIT_WORK(&ja->discard_work, journal_discard_work);
                schedule_work(&ja->discard_work);
        }
}

static void journal_reclaim(struct cache_set *c)
{
        struct bkey *k = &c->journal.key;
        struct cache *ca;
        uint64_t last_seq;
        unsigned iter, n = 0;
        atomic_t p;

        while (!atomic_read(&fifo_front(&c->journal.pin)))
                fifo_pop(&c->journal.pin, p);

        last_seq = last_seq(&c->journal);

        /* Update last_idx */

        for_each_cache(ca, c, iter) {
                struct journal_device *ja = &ca->journal;

                while (ja->last_idx != ja->cur_idx &&
                       ja->seq[ja->last_idx] < last_seq)
                        ja->last_idx = (ja->last_idx + 1) %
                                ca->sb.njournal_buckets;
        }

        for_each_cache(ca, c, iter)
                do_journal_discard(ca);

        if (c->journal.blocks_free)
                return;

        /*
         * Allocate:
         * XXX: Sort by free journal space
         */

        for_each_cache(ca, c, iter) {
                struct journal_device *ja = &ca->journal;
                unsigned next = (ja->cur_idx + 1) % ca->sb.njournal_buckets;

                /* No space available on this device */
                if (next == ja->discard_idx)
                        continue;

                ja->cur_idx = next;
                k->ptr[n++] = PTR(0,
                                  bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
                                  ca->sb.nr_this_dev);
        }

        bkey_init(k);
        SET_KEY_PTRS(k, n);

        if (n)
                c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;

        if (!journal_full(&c->journal))
                __closure_wake_up(&c->journal.wait);
}

void bch_journal_next(struct journal *j)
{
        atomic_t p = { 1 };

        j->cur = (j->cur == j->w)
                ? &j->w[1]
                : &j->w[0];

        /*
         * The fifo_push() needs to happen at the same time as j->seq is
         * incremented for last_seq() to be calculated correctly
         */
        BUG_ON(!fifo_push(&j->pin, p));
        atomic_set(&fifo_back(&j->pin), 1);

        j->cur->data->seq       = ++j->seq;
        j->cur->need_write      = false;
        j->cur->data->keys      = 0;

        if (fifo_full(&j->pin))
                pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
}

static void journal_write_endio(struct bio *bio, int error)
{
        struct journal_write *w = bio->bi_private;

        cache_set_err_on(error, w->c, "journal io error");
        closure_put(&w->c->journal.io.cl);
}

static void journal_write(struct closure *);

static void journal_write_done(struct closure *cl)
{
        struct journal *j = container_of(cl, struct journal, io.cl);
        struct cache_set *c = container_of(j, struct cache_set, journal);

        struct journal_write *w = (j->cur == j->w)
                ? &j->w[1]
                : &j->w[0];

        __closure_wake_up(&w->wait);

        if (c->journal_delay_ms)
                closure_delay(&j->io, msecs_to_jiffies(c->journal_delay_ms));

        continue_at(cl, journal_write, system_wq);
}

static void journal_write_unlocked(struct closure *cl)
        __releases(c->journal.lock)
{
        struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
        struct cache *ca;
        struct journal_write *w = c->journal.cur;
        struct bkey *k = &c->journal.key;
        unsigned i, sectors = set_blocks(w->data, c) * c->sb.block_size;

        struct bio *bio;
        struct bio_list list;
        bio_list_init(&list);

        if (!w->need_write) {
                /*
                 * XXX: have to unlock closure before we unlock journal lock,
                 * else we race with bch_journal(). But this way we race
                 * against cache set unregister. Doh.
                 */
                set_closure_fn(cl, NULL, NULL);
                closure_sub(cl, CLOSURE_RUNNING + 1);
                spin_unlock(&c->journal.lock);
                return;
        } else if (journal_full(&c->journal)) {
                journal_reclaim(c);
                spin_unlock(&c->journal.lock);

                btree_flush_write(c);
                continue_at(cl, journal_write, system_wq);
        }

        c->journal.blocks_free -= set_blocks(w->data, c);

        w->data->btree_level = c->root->level;

        bkey_copy(&w->data->btree_root, &c->root->key);
        bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);

        for_each_cache(ca, c, i)
                w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];

        w->data->magic          = jset_magic(c);
        w->data->version        = BCACHE_JSET_VERSION;
        w->data->last_seq       = last_seq(&c->journal);
        w->data->csum           = csum_set(w->data);

        for (i = 0; i < KEY_PTRS(k); i++) {
                ca = PTR_CACHE(c, k, i);
                bio = &ca->journal.bio;

                atomic_long_add(sectors, &ca->meta_sectors_written);

                bio_reset(bio);
                bio->bi_sector  = PTR_OFFSET(k, i);
                bio->bi_bdev    = ca->bdev;
                bio->bi_rw      = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
                bio->bi_size    = sectors << 9;

                bio->bi_end_io  = journal_write_endio;
                bio->bi_private = w;
                bch_bio_map(bio, w->data);

                trace_bcache_journal_write(bio);
                bio_list_add(&list, bio);

                SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);

                ca->journal.seq[ca->journal.cur_idx] = w->data->seq;
        }

        atomic_dec_bug(&fifo_back(&c->journal.pin));
        bch_journal_next(&c->journal);
        journal_reclaim(c);

        spin_unlock(&c->journal.lock);

        while ((bio = bio_list_pop(&list)))
                closure_bio_submit(bio, cl, c->cache[0]);

        continue_at(cl, journal_write_done, NULL);
}

static void journal_write(struct closure *cl)
{
        struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);

        spin_lock(&c->journal.lock);
        journal_write_unlocked(cl);
}

static void __journal_try_write(struct cache_set *c, bool noflush)
        __releases(c->journal.lock)
{
        struct closure *cl = &c->journal.io.cl;

        if (!closure_trylock(cl, &c->cl))
                spin_unlock(&c->journal.lock);
        else if (noflush && journal_full(&c->journal)) {
                spin_unlock(&c->journal.lock);
                continue_at(cl, journal_write, system_wq);
        } else
                journal_write_unlocked(cl);
}

#define journal_try_write(c)    __journal_try_write(c, false)

void bch_journal_meta(struct cache_set *c, struct closure *cl)
{
        struct journal_write *w;

        if (CACHE_SYNC(&c->sb)) {
                spin_lock(&c->journal.lock);

                w = c->journal.cur;
                w->need_write = true;

                if (cl)
                        BUG_ON(!closure_wait(&w->wait, cl));

                __journal_try_write(c, true);
        }
}

/*
 * Entry point to the journalling code - bio_insert() and btree_invalidate()
 * pass bch_journal() a list of keys to be journalled, and then
 * bch_journal() hands those same keys off to btree_insert_async()
 */

void bch_journal(struct closure *cl)
{
        struct btree_op *op = container_of(cl, struct btree_op, cl);
        struct cache_set *c = op->c;
        struct journal_write *w;
        size_t b, n = ((uint64_t *) op->keys.top) - op->keys.list;

        if (op->type != BTREE_INSERT ||
            !CACHE_SYNC(&c->sb))
                goto out;

        /*
         * If we're looping because we errored, might already be waiting on
         * another journal write:
         */
        while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
                closure_sync(cl->parent);

        spin_lock(&c->journal.lock);

        if (journal_full(&c->journal)) {
                /* XXX: tracepoint */
                closure_wait(&c->journal.wait, cl);

                journal_reclaim(c);
                spin_unlock(&c->journal.lock);

                btree_flush_write(c);
                continue_at(cl, bch_journal, bcache_wq);
        }

        w = c->journal.cur;
        w->need_write = true;
        b = __set_blocks(w->data, w->data->keys + n, c);

        if (b * c->sb.block_size > PAGE_SECTORS << JSET_BITS ||
            b > c->journal.blocks_free) {
                /* XXX: If we were inserting so many keys that they won't fit in
                 * an _empty_ journal write, we'll deadlock. For now, handle
                 * this in bch_keylist_realloc() - but something to think about.
                 */
                BUG_ON(!w->data->keys);

                /* XXX: tracepoint */
                BUG_ON(!closure_wait(&w->wait, cl));

                closure_flush(&c->journal.io);

                journal_try_write(c);
                continue_at(cl, bch_journal, bcache_wq);
        }

        memcpy(end(w->data), op->keys.list, n * sizeof(uint64_t));
        w->data->keys += n;

        op->journal = &fifo_back(&c->journal.pin);
        atomic_inc(op->journal);

        if (op->flush_journal) {
                closure_flush(&c->journal.io);
                closure_wait(&w->wait, cl->parent);
        }

        journal_try_write(c);
out:
        bch_btree_insert_async(cl);
}

void bch_journal_free(struct cache_set *c)
{
        free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
        free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
        free_fifo(&c->journal.pin);
}

int bch_journal_alloc(struct cache_set *c)
{
        struct journal *j = &c->journal;

        closure_init_unlocked(&j->io);
        spin_lock_init(&j->lock);

        c->journal_delay_ms = 100;

        j->w[0].c = c;
        j->w[1].c = c;

        if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
            !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
            !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
                return -ENOMEM;

        return 0;
}