Merge tag 'gpio-v3.13-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[linux-2.6.git] / drivers / md / bcache / writeback.c

/*
 * background writeback - scan btree for dirty data and write it to the backing
 * device
 *
 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
 * Copyright 2012 Google, Inc.
 */

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

#include <linux/delay.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <trace/events/bcache.h>

/* Rate limiting */

static void __update_writeback_rate(struct cached_dev *dc)
{
        struct cache_set *c = dc->disk.c;
        uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
        uint64_t cache_dirty_target =
                div_u64(cache_sectors * dc->writeback_percent, 100);

        int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
                                   c->cached_dev_sectors);

        /* PD controller */

        int change = 0;
        int64_t error;
        int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
        int64_t derivative = dirty - dc->disk.sectors_dirty_last;

        dc->disk.sectors_dirty_last = dirty;

        derivative *= dc->writeback_rate_d_term;
        derivative = clamp(derivative, -dirty, dirty);

        derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
                              dc->writeback_rate_d_smooth, 0);

        /* Avoid divide by zero */
        if (!target)
                goto out;

        error = div64_s64((dirty + derivative - target) << 8, target);

        change = div_s64((dc->writeback_rate.rate * error) >> 8,
                         dc->writeback_rate_p_term_inverse);

        /* Don't increase writeback rate if the device isn't keeping up */
        if (change > 0 &&
            time_after64(local_clock(),
                         dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
                change = 0;

        dc->writeback_rate.rate =
                clamp_t(int64_t, dc->writeback_rate.rate + change,
                        1, NSEC_PER_MSEC);
out:
        dc->writeback_rate_derivative = derivative;
        dc->writeback_rate_change = change;
        dc->writeback_rate_target = target;
}

static void update_writeback_rate(struct work_struct *work)
{
        struct cached_dev *dc = container_of(to_delayed_work(work),
                                             struct cached_dev,
                                             writeback_rate_update);

        down_read(&dc->writeback_lock);

        if (atomic_read(&dc->has_dirty) &&
            dc->writeback_percent)
                __update_writeback_rate(dc);

        up_read(&dc->writeback_lock);

        schedule_delayed_work(&dc->writeback_rate_update,
                              dc->writeback_rate_update_seconds * HZ);
}

static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
{
        uint64_t ret;

        if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
            !dc->writeback_percent)
                return 0;

        ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);

        return min_t(uint64_t, ret, HZ);
}

struct dirty_io {
        struct closure          cl;
        struct cached_dev       *dc;
        struct bio              bio;
};

static void dirty_init(struct keybuf_key *w)
{
        struct dirty_io *io = w->private;
        struct bio *bio = &io->bio;

        bio_init(bio);
        if (!io->dc->writeback_percent)
                bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));

        bio->bi_size            = KEY_SIZE(&w->key) << 9;
        bio->bi_max_vecs        = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
        bio->bi_private         = w;
        bio->bi_io_vec          = bio->bi_inline_vecs;
        bch_bio_map(bio, NULL);
}

static void dirty_io_destructor(struct closure *cl)
{
        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
        kfree(io);
}

static void write_dirty_finish(struct closure *cl)
{
        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
        struct keybuf_key *w = io->bio.bi_private;
        struct cached_dev *dc = io->dc;
        struct bio_vec *bv;
        int i;

        bio_for_each_segment_all(bv, &io->bio, i)
                __free_page(bv->bv_page);

        /* This is kind of a dumb way of signalling errors. */
        if (KEY_DIRTY(&w->key)) {
                int ret;
                unsigned i;
                struct keylist keys;

                bch_keylist_init(&keys);

                bkey_copy(keys.top, &w->key);
                SET_KEY_DIRTY(keys.top, false);
                bch_keylist_push(&keys);

                for (i = 0; i < KEY_PTRS(&w->key); i++)
                        atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);

                ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);

                if (ret)
                        trace_bcache_writeback_collision(&w->key);

                atomic_long_inc(ret
                                ? &dc->disk.c->writeback_keys_failed
                                : &dc->disk.c->writeback_keys_done);
        }

        bch_keybuf_del(&dc->writeback_keys, w);
        up(&dc->in_flight);

        closure_return_with_destructor(cl, dirty_io_destructor);
}

static void dirty_endio(struct bio *bio, int error)
{
        struct keybuf_key *w = bio->bi_private;
        struct dirty_io *io = w->private;

        if (error)
                SET_KEY_DIRTY(&w->key, false);

        closure_put(&io->cl);
}

static void write_dirty(struct closure *cl)
{
        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
        struct keybuf_key *w = io->bio.bi_private;

        dirty_init(w);
        io->bio.bi_rw           = WRITE;
        io->bio.bi_sector       = KEY_START(&w->key);
        io->bio.bi_bdev         = io->dc->bdev;
        io->bio.bi_end_io       = dirty_endio;

        closure_bio_submit(&io->bio, cl, &io->dc->disk);

        continue_at(cl, write_dirty_finish, system_wq);
}

static void read_dirty_endio(struct bio *bio, int error)
{
        struct keybuf_key *w = bio->bi_private;
        struct dirty_io *io = w->private;

        bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
                            error, "reading dirty data from cache");

        dirty_endio(bio, error);
}

static void read_dirty_submit(struct closure *cl)
{
        struct dirty_io *io = container_of(cl, struct dirty_io, cl);

        closure_bio_submit(&io->bio, cl, &io->dc->disk);

        continue_at(cl, write_dirty, system_wq);
}

static void read_dirty(struct cached_dev *dc)
{
        unsigned delay = 0;
        struct keybuf_key *w;
        struct dirty_io *io;
        struct closure cl;

        closure_init_stack(&cl);

        /*
         * XXX: if we error, background writeback just spins. Should use some
         * mempools.
         */

        while (!kthread_should_stop()) {
                try_to_freeze();

                w = bch_keybuf_next(&dc->writeback_keys);
                if (!w)
                        break;

                BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));

                if (KEY_START(&w->key) != dc->last_read ||
                    jiffies_to_msecs(delay) > 50)
                        while (!kthread_should_stop() && delay)
                                delay = schedule_timeout_interruptible(delay);

                dc->last_read   = KEY_OFFSET(&w->key);

                io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
                             * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
                             GFP_KERNEL);
                if (!io)
                        goto err;

                w->private      = io;
                io->dc          = dc;

                dirty_init(w);
                io->bio.bi_sector       = PTR_OFFSET(&w->key, 0);
                io->bio.bi_bdev         = PTR_CACHE(dc->disk.c,
                                                    &w->key, 0)->bdev;
                io->bio.bi_rw           = READ;
                io->bio.bi_end_io       = read_dirty_endio;

                if (bio_alloc_pages(&io->bio, GFP_KERNEL))
                        goto err_free;

                trace_bcache_writeback(&w->key);

                down(&dc->in_flight);
                closure_call(&io->cl, read_dirty_submit, NULL, &cl);

                delay = writeback_delay(dc, KEY_SIZE(&w->key));
        }

        if (0) {
err_free:
                kfree(w->private);
err:
                bch_keybuf_del(&dc->writeback_keys, w);
        }

        /*
         * Wait for outstanding writeback IOs to finish (and keybuf slots to be
         * freed) before refilling again
         */
        closure_sync(&cl);
}

/* Scan for dirty data */

void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
                                  uint64_t offset, int nr_sectors)
{
        struct bcache_device *d = c->devices[inode];
        unsigned stripe_offset, stripe, sectors_dirty;

        if (!d)
                return;

        stripe = offset_to_stripe(d, offset);
        stripe_offset = offset & (d->stripe_size - 1);

        while (nr_sectors) {
                int s = min_t(unsigned, abs(nr_sectors),
                              d->stripe_size - stripe_offset);

                if (nr_sectors < 0)
                        s = -s;

                if (stripe >= d->nr_stripes)
                        return;

                sectors_dirty = atomic_add_return(s,
                                        d->stripe_sectors_dirty + stripe);
                if (sectors_dirty == d->stripe_size)
                        set_bit(stripe, d->full_dirty_stripes);
                else
                        clear_bit(stripe, d->full_dirty_stripes);

                nr_sectors -= s;
                stripe_offset = 0;
                stripe++;
        }
}

static bool dirty_pred(struct keybuf *buf, struct bkey *k)
{
        return KEY_DIRTY(k);
}

static void refill_full_stripes(struct cached_dev *dc)
{
        struct keybuf *buf = &dc->writeback_keys;
        unsigned start_stripe, stripe, next_stripe;
        bool wrapped = false;

        stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));

        if (stripe >= dc->disk.nr_stripes)
                stripe = 0;

        start_stripe = stripe;

        while (1) {
                stripe = find_next_bit(dc->disk.full_dirty_stripes,
                                       dc->disk.nr_stripes, stripe);

                if (stripe == dc->disk.nr_stripes)
                        goto next;

                next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
                                                 dc->disk.nr_stripes, stripe);

                buf->last_scanned = KEY(dc->disk.id,
                                        stripe * dc->disk.stripe_size, 0);

                bch_refill_keybuf(dc->disk.c, buf,
                                  &KEY(dc->disk.id,
                                       next_stripe * dc->disk.stripe_size, 0),
                                  dirty_pred);

                if (array_freelist_empty(&buf->freelist))
                        return;

                stripe = next_stripe;
next:
                if (wrapped && stripe > start_stripe)
                        return;

                if (stripe == dc->disk.nr_stripes) {
                        stripe = 0;
                        wrapped = true;
                }
        }
}

static bool refill_dirty(struct cached_dev *dc)
{
        struct keybuf *buf = &dc->writeback_keys;
        struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
        bool searched_from_start = false;

        if (dc->partial_stripes_expensive) {
                refill_full_stripes(dc);
                if (array_freelist_empty(&buf->freelist))
                        return false;
        }

        if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
                buf->last_scanned = KEY(dc->disk.id, 0, 0);
                searched_from_start = true;
        }

        bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);

        return bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start;
}

static int bch_writeback_thread(void *arg)
{
        struct cached_dev *dc = arg;
        bool searched_full_index;

        while (!kthread_should_stop()) {
                down_write(&dc->writeback_lock);
                if (!atomic_read(&dc->has_dirty) ||
                    (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
                     !dc->writeback_running)) {
                        up_write(&dc->writeback_lock);
                        set_current_state(TASK_INTERRUPTIBLE);

                        if (kthread_should_stop())
                                return 0;

                        try_to_freeze();
                        schedule();
                        continue;
                }

                searched_full_index = refill_dirty(dc);

                if (searched_full_index &&
                    RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
                        atomic_set(&dc->has_dirty, 0);
                        cached_dev_put(dc);
                        SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
                        bch_write_bdev_super(dc, NULL);
                }

                up_write(&dc->writeback_lock);

                bch_ratelimit_reset(&dc->writeback_rate);
                read_dirty(dc);

                if (searched_full_index) {
                        unsigned delay = dc->writeback_delay * HZ;

                        while (delay &&
                               !kthread_should_stop() &&
                               !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
                                delay = schedule_timeout_interruptible(delay);
                }
        }

        return 0;
}

/* Init */

struct sectors_dirty_init {
        struct btree_op op;
        unsigned        inode;
};

static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
                                 struct bkey *k)
{
        struct sectors_dirty_init *op = container_of(_op,
                                                struct sectors_dirty_init, op);
        if (KEY_INODE(k) > op->inode)
                return MAP_DONE;

        if (KEY_DIRTY(k))
                bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
                                             KEY_START(k), KEY_SIZE(k));

        return MAP_CONTINUE;
}

void bch_sectors_dirty_init(struct cached_dev *dc)
{
        struct sectors_dirty_init op;

        bch_btree_op_init(&op.op, -1);
        op.inode = dc->disk.id;

        bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0),
                           sectors_dirty_init_fn, 0);
}

int bch_cached_dev_writeback_init(struct cached_dev *dc)
{
        sema_init(&dc->in_flight, 64);
        init_rwsem(&dc->writeback_lock);
        bch_keybuf_init(&dc->writeback_keys);

        dc->writeback_metadata          = true;
        dc->writeback_running           = true;
        dc->writeback_percent           = 10;
        dc->writeback_delay             = 30;
        dc->writeback_rate.rate         = 1024;

        dc->writeback_rate_update_seconds = 30;
        dc->writeback_rate_d_term       = 16;
        dc->writeback_rate_p_term_inverse = 64;
        dc->writeback_rate_d_smooth     = 8;

        dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
                                              "bcache_writeback");
        if (IS_ERR(dc->writeback_thread))
                return PTR_ERR(dc->writeback_thread);

        set_task_state(dc->writeback_thread, TASK_INTERRUPTIBLE);

        INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
        schedule_delayed_work(&dc->writeback_rate_update,
                              dc->writeback_rate_update_seconds * HZ);

        return 0;
}