linux/drivers/md/bcache/writeback.c
Kent Overstreet 8e51e414a3 bcache: Use standard utility code
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>
2013-07-01 14:43:53 -07:00

522 lines
12 KiB
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 <trace/events/bcache.h>
static struct workqueue_struct *dirty_wq;
static void read_dirty(struct closure *);
struct dirty_io {
struct closure cl;
struct cached_dev *dc;
struct bio bio;
};
/* 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;
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);
}
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);
}
static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
{
if (atomic_read(&dc->disk.detaching) ||
!dc->writeback_percent)
return 0;
return bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);
}
/* Background writeback */
static bool dirty_pred(struct keybuf *buf, struct bkey *k)
{
return KEY_DIRTY(k);
}
static bool dirty_full_stripe_pred(struct keybuf *buf, struct bkey *k)
{
uint64_t stripe;
unsigned nr_sectors = KEY_SIZE(k);
struct cached_dev *dc = container_of(buf, struct cached_dev,
writeback_keys);
unsigned stripe_size = 1 << dc->disk.stripe_size_bits;
if (!KEY_DIRTY(k))
return false;
stripe = KEY_START(k) >> dc->disk.stripe_size_bits;
while (1) {
if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) !=
stripe_size)
return false;
if (nr_sectors <= stripe_size)
return true;
nr_sectors -= stripe_size;
stripe++;
}
}
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 refill_dirty(struct closure *cl)
{
struct cached_dev *dc = container_of(cl, struct cached_dev,
writeback.cl);
struct keybuf *buf = &dc->writeback_keys;
bool searched_from_start = false;
struct bkey end = MAX_KEY;
SET_KEY_INODE(&end, dc->disk.id);
if (!atomic_read(&dc->disk.detaching) &&
!dc->writeback_running)
closure_return(cl);
down_write(&dc->writeback_lock);
if (!atomic_read(&dc->has_dirty)) {
SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
bch_write_bdev_super(dc, NULL);
up_write(&dc->writeback_lock);
closure_return(cl);
}
if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
buf->last_scanned = KEY(dc->disk.id, 0, 0);
searched_from_start = true;
}
if (dc->partial_stripes_expensive) {
uint64_t i;
for (i = 0; i < dc->disk.nr_stripes; i++)
if (atomic_read(dc->disk.stripe_sectors_dirty + i) ==
1 << dc->disk.stripe_size_bits)
goto full_stripes;
goto normal_refill;
full_stripes:
bch_refill_keybuf(dc->disk.c, buf, &end,
dirty_full_stripe_pred);
} else {
normal_refill:
bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
}
if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) {
/* Searched the entire btree - delay awhile */
if (RB_EMPTY_ROOT(&buf->keys)) {
atomic_set(&dc->has_dirty, 0);
cached_dev_put(dc);
}
if (!atomic_read(&dc->disk.detaching))
closure_delay(&dc->writeback, dc->writeback_delay * HZ);
}
up_write(&dc->writeback_lock);
ratelimit_reset(&dc->writeback_rate);
/* Punt to workqueue only so we don't recurse and blow the stack */
continue_at(cl, read_dirty, dirty_wq);
}
void bch_writeback_queue(struct cached_dev *dc)
{
if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) {
if (!atomic_read(&dc->disk.detaching))
closure_delay(&dc->writeback, dc->writeback_delay * HZ);
continue_at(&dc->writeback.cl, refill_dirty, dirty_wq);
}
}
void bch_writeback_add(struct cached_dev *dc)
{
if (!atomic_read(&dc->has_dirty) &&
!atomic_xchg(&dc->has_dirty, 1)) {
atomic_inc(&dc->count);
if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
/* XXX: should do this synchronously */
bch_write_bdev_super(dc, NULL);
}
bch_writeback_queue(dc);
if (dc->writeback_percent)
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);
}
}
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_size, stripe_offset;
uint64_t stripe;
if (!d)
return;
stripe_size = 1 << d->stripe_size_bits;
stripe = offset >> d->stripe_size_bits;
stripe_offset = offset & (stripe_size - 1);
while (nr_sectors) {
int s = min_t(unsigned, abs(nr_sectors),
stripe_size - stripe_offset);
if (nr_sectors < 0)
s = -s;
atomic_add(s, d->stripe_sectors_dirty + stripe);
nr_sectors -= s;
stripe_offset = 0;
stripe++;
}
}
/* Background writeback - IO loop */
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)) {
unsigned i;
struct btree_op op;
bch_btree_op_init_stack(&op);
op.type = BTREE_REPLACE;
bkey_copy(&op.replace, &w->key);
SET_KEY_DIRTY(&w->key, false);
bch_keylist_add(&op.keys, &w->key);
for (i = 0; i < KEY_PTRS(&w->key); i++)
atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
bch_btree_insert(&op, dc->disk.c);
closure_sync(&op.cl);
if (op.insert_collision)
trace_bcache_writeback_collision(&w->key);
atomic_long_inc(op.insert_collision
? &dc->disk.c->writeback_keys_failed
: &dc->disk.c->writeback_keys_done);
}
bch_keybuf_del(&dc->writeback_keys, w);
atomic_dec_bug(&dc->in_flight);
closure_wake_up(&dc->writeback_wait);
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, dirty_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, dirty_wq);
}
static void read_dirty(struct closure *cl)
{
struct cached_dev *dc = container_of(cl, struct cached_dev,
writeback.cl);
unsigned delay = writeback_delay(dc, 0);
struct keybuf_key *w;
struct dirty_io *io;
/*
* XXX: if we error, background writeback just spins. Should use some
* mempools.
*/
while (1) {
w = bch_keybuf_next(&dc->writeback_keys);
if (!w)
break;
BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
if (delay > 0 &&
(KEY_START(&w->key) != dc->last_read ||
jiffies_to_msecs(delay) > 50)) {
w->private = NULL;
closure_delay(&dc->writeback, delay);
continue_at(cl, read_dirty, dirty_wq);
}
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);
closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl);
delay = writeback_delay(dc, KEY_SIZE(&w->key));
atomic_inc(&dc->in_flight);
if (!closure_wait_event(&dc->writeback_wait, cl,
atomic_read(&dc->in_flight) < 64))
continue_at(cl, read_dirty, dirty_wq);
}
if (0) {
err_free:
kfree(w->private);
err:
bch_keybuf_del(&dc->writeback_keys, w);
}
refill_dirty(cl);
}
/* Init */
static int bch_btree_sectors_dirty_init(struct btree *b, struct btree_op *op,
struct cached_dev *dc)
{
struct bkey *k;
struct btree_iter iter;
bch_btree_iter_init(b, &iter, &KEY(dc->disk.id, 0, 0));
while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad)))
if (!b->level) {
if (KEY_INODE(k) > dc->disk.id)
break;
if (KEY_DIRTY(k))
bcache_dev_sectors_dirty_add(b->c, dc->disk.id,
KEY_START(k),
KEY_SIZE(k));
} else {
btree(sectors_dirty_init, k, b, op, dc);
if (KEY_INODE(k) > dc->disk.id)
break;
cond_resched();
}
return 0;
}
void bch_sectors_dirty_init(struct cached_dev *dc)
{
struct btree_op op;
bch_btree_op_init_stack(&op);
btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
}
void bch_cached_dev_writeback_init(struct cached_dev *dc)
{
closure_init_unlocked(&dc->writeback);
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;
INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);
}
void bch_writeback_exit(void)
{
if (dirty_wq)
destroy_workqueue(dirty_wq);
}
int __init bch_writeback_init(void)
{
dirty_wq = create_singlethread_workqueue("bcache_writeback");
if (!dirty_wq)
return -ENOMEM;
return 0;
}