![Kent Overstreet](/assets/img/avatar_default.png)
Some of bcache's utility code has made it into the rest of the kernel, so drop the bcache versions. Bcache used to have a workaround for allocating from a bio set under generic_make_request() (if you allocated more than once, the bios you already allocated would get stuck on current->bio_list when you submitted, and you'd risk deadlock) - bcache would mask out __GFP_WAIT when allocating bios under generic_make_request() so that allocation could fail and it could retry from workqueue. But bio_alloc_bioset() has a workaround now, so we can drop this hack and the associated error handling. Signed-off-by: Kent Overstreet <koverstreet@google.com>
522 lines
12 KiB
C
522 lines
12 KiB
C
/*
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* background writeback - scan btree for dirty data and write it to the backing
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* device
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*
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* Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
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* Copyright 2012 Google, Inc.
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*/
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#include "bcache.h"
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#include "btree.h"
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#include "debug.h"
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#include "writeback.h"
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#include <trace/events/bcache.h>
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static struct workqueue_struct *dirty_wq;
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static void read_dirty(struct closure *);
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struct dirty_io {
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struct closure cl;
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struct cached_dev *dc;
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struct bio bio;
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};
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/* Rate limiting */
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static void __update_writeback_rate(struct cached_dev *dc)
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{
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struct cache_set *c = dc->disk.c;
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uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
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uint64_t cache_dirty_target =
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div_u64(cache_sectors * dc->writeback_percent, 100);
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int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
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c->cached_dev_sectors);
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/* PD controller */
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int change = 0;
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int64_t error;
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int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
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int64_t derivative = dirty - dc->disk.sectors_dirty_last;
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dc->disk.sectors_dirty_last = dirty;
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derivative *= dc->writeback_rate_d_term;
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derivative = clamp(derivative, -dirty, dirty);
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derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
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dc->writeback_rate_d_smooth, 0);
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/* Avoid divide by zero */
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if (!target)
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goto out;
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error = div64_s64((dirty + derivative - target) << 8, target);
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change = div_s64((dc->writeback_rate.rate * error) >> 8,
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dc->writeback_rate_p_term_inverse);
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/* Don't increase writeback rate if the device isn't keeping up */
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if (change > 0 &&
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time_after64(local_clock(),
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dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
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change = 0;
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dc->writeback_rate.rate =
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clamp_t(int64_t, dc->writeback_rate.rate + change,
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1, NSEC_PER_MSEC);
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out:
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dc->writeback_rate_derivative = derivative;
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dc->writeback_rate_change = change;
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dc->writeback_rate_target = target;
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schedule_delayed_work(&dc->writeback_rate_update,
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dc->writeback_rate_update_seconds * HZ);
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}
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static void update_writeback_rate(struct work_struct *work)
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{
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struct cached_dev *dc = container_of(to_delayed_work(work),
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struct cached_dev,
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writeback_rate_update);
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down_read(&dc->writeback_lock);
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if (atomic_read(&dc->has_dirty) &&
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dc->writeback_percent)
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__update_writeback_rate(dc);
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up_read(&dc->writeback_lock);
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}
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static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
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{
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if (atomic_read(&dc->disk.detaching) ||
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!dc->writeback_percent)
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return 0;
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return bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);
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}
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/* Background writeback */
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static bool dirty_pred(struct keybuf *buf, struct bkey *k)
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{
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return KEY_DIRTY(k);
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}
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static bool dirty_full_stripe_pred(struct keybuf *buf, struct bkey *k)
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{
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uint64_t stripe;
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unsigned nr_sectors = KEY_SIZE(k);
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struct cached_dev *dc = container_of(buf, struct cached_dev,
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writeback_keys);
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unsigned stripe_size = 1 << dc->disk.stripe_size_bits;
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if (!KEY_DIRTY(k))
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return false;
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stripe = KEY_START(k) >> dc->disk.stripe_size_bits;
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while (1) {
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if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) !=
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stripe_size)
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return false;
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if (nr_sectors <= stripe_size)
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return true;
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nr_sectors -= stripe_size;
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stripe++;
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}
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}
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static void dirty_init(struct keybuf_key *w)
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{
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struct dirty_io *io = w->private;
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struct bio *bio = &io->bio;
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bio_init(bio);
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if (!io->dc->writeback_percent)
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bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
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bio->bi_size = KEY_SIZE(&w->key) << 9;
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bio->bi_max_vecs = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
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bio->bi_private = w;
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bio->bi_io_vec = bio->bi_inline_vecs;
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bch_bio_map(bio, NULL);
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}
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static void refill_dirty(struct closure *cl)
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{
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struct cached_dev *dc = container_of(cl, struct cached_dev,
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writeback.cl);
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struct keybuf *buf = &dc->writeback_keys;
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bool searched_from_start = false;
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struct bkey end = MAX_KEY;
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SET_KEY_INODE(&end, dc->disk.id);
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if (!atomic_read(&dc->disk.detaching) &&
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!dc->writeback_running)
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closure_return(cl);
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down_write(&dc->writeback_lock);
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if (!atomic_read(&dc->has_dirty)) {
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SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
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bch_write_bdev_super(dc, NULL);
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up_write(&dc->writeback_lock);
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closure_return(cl);
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}
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if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
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buf->last_scanned = KEY(dc->disk.id, 0, 0);
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searched_from_start = true;
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}
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if (dc->partial_stripes_expensive) {
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uint64_t i;
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for (i = 0; i < dc->disk.nr_stripes; i++)
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if (atomic_read(dc->disk.stripe_sectors_dirty + i) ==
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1 << dc->disk.stripe_size_bits)
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goto full_stripes;
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goto normal_refill;
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full_stripes:
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bch_refill_keybuf(dc->disk.c, buf, &end,
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dirty_full_stripe_pred);
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} else {
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normal_refill:
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bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
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}
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if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) {
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/* Searched the entire btree - delay awhile */
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if (RB_EMPTY_ROOT(&buf->keys)) {
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atomic_set(&dc->has_dirty, 0);
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cached_dev_put(dc);
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}
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if (!atomic_read(&dc->disk.detaching))
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closure_delay(&dc->writeback, dc->writeback_delay * HZ);
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}
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up_write(&dc->writeback_lock);
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ratelimit_reset(&dc->writeback_rate);
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/* Punt to workqueue only so we don't recurse and blow the stack */
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continue_at(cl, read_dirty, dirty_wq);
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}
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void bch_writeback_queue(struct cached_dev *dc)
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{
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if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) {
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if (!atomic_read(&dc->disk.detaching))
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closure_delay(&dc->writeback, dc->writeback_delay * HZ);
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continue_at(&dc->writeback.cl, refill_dirty, dirty_wq);
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}
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}
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void bch_writeback_add(struct cached_dev *dc)
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{
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if (!atomic_read(&dc->has_dirty) &&
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!atomic_xchg(&dc->has_dirty, 1)) {
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atomic_inc(&dc->count);
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if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
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SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
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/* XXX: should do this synchronously */
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bch_write_bdev_super(dc, NULL);
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}
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bch_writeback_queue(dc);
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if (dc->writeback_percent)
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schedule_delayed_work(&dc->writeback_rate_update,
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dc->writeback_rate_update_seconds * HZ);
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}
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}
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void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
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uint64_t offset, int nr_sectors)
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{
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struct bcache_device *d = c->devices[inode];
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unsigned stripe_size, stripe_offset;
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uint64_t stripe;
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if (!d)
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return;
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stripe_size = 1 << d->stripe_size_bits;
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stripe = offset >> d->stripe_size_bits;
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stripe_offset = offset & (stripe_size - 1);
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while (nr_sectors) {
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int s = min_t(unsigned, abs(nr_sectors),
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stripe_size - stripe_offset);
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if (nr_sectors < 0)
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s = -s;
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atomic_add(s, d->stripe_sectors_dirty + stripe);
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nr_sectors -= s;
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stripe_offset = 0;
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stripe++;
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}
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}
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/* Background writeback - IO loop */
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static void dirty_io_destructor(struct closure *cl)
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{
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struct dirty_io *io = container_of(cl, struct dirty_io, cl);
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kfree(io);
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}
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static void write_dirty_finish(struct closure *cl)
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{
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struct dirty_io *io = container_of(cl, struct dirty_io, cl);
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struct keybuf_key *w = io->bio.bi_private;
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struct cached_dev *dc = io->dc;
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struct bio_vec *bv;
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int i;
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bio_for_each_segment_all(bv, &io->bio, i)
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__free_page(bv->bv_page);
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/* This is kind of a dumb way of signalling errors. */
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if (KEY_DIRTY(&w->key)) {
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unsigned i;
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struct btree_op op;
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bch_btree_op_init_stack(&op);
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op.type = BTREE_REPLACE;
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bkey_copy(&op.replace, &w->key);
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SET_KEY_DIRTY(&w->key, false);
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bch_keylist_add(&op.keys, &w->key);
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for (i = 0; i < KEY_PTRS(&w->key); i++)
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atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
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bch_btree_insert(&op, dc->disk.c);
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closure_sync(&op.cl);
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if (op.insert_collision)
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trace_bcache_writeback_collision(&w->key);
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atomic_long_inc(op.insert_collision
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? &dc->disk.c->writeback_keys_failed
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: &dc->disk.c->writeback_keys_done);
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}
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bch_keybuf_del(&dc->writeback_keys, w);
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atomic_dec_bug(&dc->in_flight);
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closure_wake_up(&dc->writeback_wait);
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closure_return_with_destructor(cl, dirty_io_destructor);
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}
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static void dirty_endio(struct bio *bio, int error)
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{
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struct keybuf_key *w = bio->bi_private;
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struct dirty_io *io = w->private;
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if (error)
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SET_KEY_DIRTY(&w->key, false);
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closure_put(&io->cl);
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}
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static void write_dirty(struct closure *cl)
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{
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struct dirty_io *io = container_of(cl, struct dirty_io, cl);
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struct keybuf_key *w = io->bio.bi_private;
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dirty_init(w);
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io->bio.bi_rw = WRITE;
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io->bio.bi_sector = KEY_START(&w->key);
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io->bio.bi_bdev = io->dc->bdev;
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io->bio.bi_end_io = dirty_endio;
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closure_bio_submit(&io->bio, cl, &io->dc->disk);
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continue_at(cl, write_dirty_finish, dirty_wq);
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}
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static void read_dirty_endio(struct bio *bio, int error)
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{
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struct keybuf_key *w = bio->bi_private;
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struct dirty_io *io = w->private;
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bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
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error, "reading dirty data from cache");
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dirty_endio(bio, error);
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}
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static void read_dirty_submit(struct closure *cl)
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{
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struct dirty_io *io = container_of(cl, struct dirty_io, cl);
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closure_bio_submit(&io->bio, cl, &io->dc->disk);
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continue_at(cl, write_dirty, dirty_wq);
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}
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static void read_dirty(struct closure *cl)
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{
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struct cached_dev *dc = container_of(cl, struct cached_dev,
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writeback.cl);
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unsigned delay = writeback_delay(dc, 0);
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struct keybuf_key *w;
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struct dirty_io *io;
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/*
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* XXX: if we error, background writeback just spins. Should use some
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* mempools.
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*/
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while (1) {
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w = bch_keybuf_next(&dc->writeback_keys);
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if (!w)
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break;
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BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
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if (delay > 0 &&
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(KEY_START(&w->key) != dc->last_read ||
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jiffies_to_msecs(delay) > 50)) {
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w->private = NULL;
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closure_delay(&dc->writeback, delay);
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continue_at(cl, read_dirty, dirty_wq);
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}
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dc->last_read = KEY_OFFSET(&w->key);
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io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
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* DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
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GFP_KERNEL);
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if (!io)
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goto err;
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w->private = io;
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io->dc = dc;
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dirty_init(w);
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io->bio.bi_sector = PTR_OFFSET(&w->key, 0);
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io->bio.bi_bdev = PTR_CACHE(dc->disk.c,
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&w->key, 0)->bdev;
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io->bio.bi_rw = READ;
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io->bio.bi_end_io = read_dirty_endio;
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if (bio_alloc_pages(&io->bio, GFP_KERNEL))
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goto err_free;
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trace_bcache_writeback(&w->key);
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closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl);
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delay = writeback_delay(dc, KEY_SIZE(&w->key));
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atomic_inc(&dc->in_flight);
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if (!closure_wait_event(&dc->writeback_wait, cl,
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atomic_read(&dc->in_flight) < 64))
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continue_at(cl, read_dirty, dirty_wq);
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}
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if (0) {
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err_free:
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kfree(w->private);
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err:
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bch_keybuf_del(&dc->writeback_keys, w);
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}
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refill_dirty(cl);
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}
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/* Init */
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static int bch_btree_sectors_dirty_init(struct btree *b, struct btree_op *op,
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struct cached_dev *dc)
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{
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struct bkey *k;
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struct btree_iter iter;
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bch_btree_iter_init(b, &iter, &KEY(dc->disk.id, 0, 0));
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while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad)))
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if (!b->level) {
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if (KEY_INODE(k) > dc->disk.id)
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break;
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if (KEY_DIRTY(k))
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bcache_dev_sectors_dirty_add(b->c, dc->disk.id,
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KEY_START(k),
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KEY_SIZE(k));
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} else {
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btree(sectors_dirty_init, k, b, op, dc);
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if (KEY_INODE(k) > dc->disk.id)
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break;
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cond_resched();
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}
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return 0;
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}
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void bch_sectors_dirty_init(struct cached_dev *dc)
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{
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struct btree_op op;
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bch_btree_op_init_stack(&op);
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btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
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}
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void bch_cached_dev_writeback_init(struct cached_dev *dc)
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{
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closure_init_unlocked(&dc->writeback);
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init_rwsem(&dc->writeback_lock);
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bch_keybuf_init(&dc->writeback_keys);
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dc->writeback_metadata = true;
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dc->writeback_running = true;
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dc->writeback_percent = 10;
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dc->writeback_delay = 30;
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dc->writeback_rate.rate = 1024;
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dc->writeback_rate_update_seconds = 30;
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dc->writeback_rate_d_term = 16;
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dc->writeback_rate_p_term_inverse = 64;
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dc->writeback_rate_d_smooth = 8;
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INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
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schedule_delayed_work(&dc->writeback_rate_update,
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dc->writeback_rate_update_seconds * HZ);
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}
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void bch_writeback_exit(void)
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{
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if (dirty_wq)
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destroy_workqueue(dirty_wq);
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}
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int __init bch_writeback_init(void)
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{
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dirty_wq = create_singlethread_workqueue("bcache_writeback");
|
|
if (!dirty_wq)
|
|
return -ENOMEM;
|
|
|
|
return 0;
|
|
}
|