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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/md/bcache/writeback.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/md/bcache/writeback.c')
-rw-r--r--drivers/md/bcache/writeback.c1100
1 files changed, 1100 insertions, 0 deletions
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
new file mode 100644
index 0000000000..3accfdaee6
--- /dev/null
+++ b/drivers/md/bcache/writeback.c
@@ -0,0 +1,1100 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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/kthread.h>
+#include <linux/sched/clock.h>
+#include <trace/events/bcache.h>
+
+static void update_gc_after_writeback(struct cache_set *c)
+{
+ if (c->gc_after_writeback != (BCH_ENABLE_AUTO_GC) ||
+ c->gc_stats.in_use < BCH_AUTO_GC_DIRTY_THRESHOLD)
+ return;
+
+ c->gc_after_writeback |= BCH_DO_AUTO_GC;
+}
+
+/* Rate limiting */
+static uint64_t __calc_target_rate(struct cached_dev *dc)
+{
+ struct cache_set *c = dc->disk.c;
+
+ /*
+ * This is the size of the cache, minus the amount used for
+ * flash-only devices
+ */
+ uint64_t cache_sectors = c->nbuckets * c->cache->sb.bucket_size -
+ atomic_long_read(&c->flash_dev_dirty_sectors);
+
+ /*
+ * Unfortunately there is no control of global dirty data. If the
+ * user states that they want 10% dirty data in the cache, and has,
+ * e.g., 5 backing volumes of equal size, we try and ensure each
+ * backing volume uses about 2% of the cache for dirty data.
+ */
+ uint32_t bdev_share =
+ div64_u64(bdev_nr_sectors(dc->bdev) << WRITEBACK_SHARE_SHIFT,
+ c->cached_dev_sectors);
+
+ uint64_t cache_dirty_target =
+ div_u64(cache_sectors * dc->writeback_percent, 100);
+
+ /* Ensure each backing dev gets at least one dirty share */
+ if (bdev_share < 1)
+ bdev_share = 1;
+
+ return (cache_dirty_target * bdev_share) >> WRITEBACK_SHARE_SHIFT;
+}
+
+static void __update_writeback_rate(struct cached_dev *dc)
+{
+ /*
+ * PI controller:
+ * Figures out the amount that should be written per second.
+ *
+ * First, the error (number of sectors that are dirty beyond our
+ * target) is calculated. The error is accumulated (numerically
+ * integrated).
+ *
+ * Then, the proportional value and integral value are scaled
+ * based on configured values. These are stored as inverses to
+ * avoid fixed point math and to make configuration easy-- e.g.
+ * the default value of 40 for writeback_rate_p_term_inverse
+ * attempts to write at a rate that would retire all the dirty
+ * blocks in 40 seconds.
+ *
+ * The writeback_rate_i_inverse value of 10000 means that 1/10000th
+ * of the error is accumulated in the integral term per second.
+ * This acts as a slow, long-term average that is not subject to
+ * variations in usage like the p term.
+ */
+ int64_t target = __calc_target_rate(dc);
+ int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
+ int64_t error = dirty - target;
+ int64_t proportional_scaled =
+ div_s64(error, dc->writeback_rate_p_term_inverse);
+ int64_t integral_scaled;
+ uint32_t new_rate;
+
+ /*
+ * We need to consider the number of dirty buckets as well
+ * when calculating the proportional_scaled, Otherwise we might
+ * have an unreasonable small writeback rate at a highly fragmented situation
+ * when very few dirty sectors consumed a lot dirty buckets, the
+ * worst case is when dirty buckets reached cutoff_writeback_sync and
+ * dirty data is still not even reached to writeback percent, so the rate
+ * still will be at the minimum value, which will cause the write
+ * stuck at a non-writeback mode.
+ */
+ struct cache_set *c = dc->disk.c;
+
+ int64_t dirty_buckets = c->nbuckets - c->avail_nbuckets;
+
+ if (dc->writeback_consider_fragment &&
+ c->gc_stats.in_use > BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW && dirty > 0) {
+ int64_t fragment =
+ div_s64((dirty_buckets * c->cache->sb.bucket_size), dirty);
+ int64_t fp_term;
+ int64_t fps;
+
+ if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID) {
+ fp_term = (int64_t)dc->writeback_rate_fp_term_low *
+ (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW);
+ } else if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH) {
+ fp_term = (int64_t)dc->writeback_rate_fp_term_mid *
+ (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID);
+ } else {
+ fp_term = (int64_t)dc->writeback_rate_fp_term_high *
+ (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH);
+ }
+ fps = div_s64(dirty, dirty_buckets) * fp_term;
+ if (fragment > 3 && fps > proportional_scaled) {
+ /* Only overrite the p when fragment > 3 */
+ proportional_scaled = fps;
+ }
+ }
+
+ if ((error < 0 && dc->writeback_rate_integral > 0) ||
+ (error > 0 && time_before64(local_clock(),
+ dc->writeback_rate.next + NSEC_PER_MSEC))) {
+ /*
+ * Only decrease the integral term if it's more than
+ * zero. Only increase the integral term if the device
+ * is keeping up. (Don't wind up the integral
+ * ineffectively in either case).
+ *
+ * It's necessary to scale this by
+ * writeback_rate_update_seconds to keep the integral
+ * term dimensioned properly.
+ */
+ dc->writeback_rate_integral += error *
+ dc->writeback_rate_update_seconds;
+ }
+
+ integral_scaled = div_s64(dc->writeback_rate_integral,
+ dc->writeback_rate_i_term_inverse);
+
+ new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
+ dc->writeback_rate_minimum, NSEC_PER_SEC);
+
+ dc->writeback_rate_proportional = proportional_scaled;
+ dc->writeback_rate_integral_scaled = integral_scaled;
+ dc->writeback_rate_change = new_rate -
+ atomic_long_read(&dc->writeback_rate.rate);
+ atomic_long_set(&dc->writeback_rate.rate, new_rate);
+ dc->writeback_rate_target = target;
+}
+
+static bool idle_counter_exceeded(struct cache_set *c)
+{
+ int counter, dev_nr;
+
+ /*
+ * If c->idle_counter is overflow (idel for really long time),
+ * reset as 0 and not set maximum rate this time for code
+ * simplicity.
+ */
+ counter = atomic_inc_return(&c->idle_counter);
+ if (counter <= 0) {
+ atomic_set(&c->idle_counter, 0);
+ return false;
+ }
+
+ dev_nr = atomic_read(&c->attached_dev_nr);
+ if (dev_nr == 0)
+ return false;
+
+ /*
+ * c->idle_counter is increased by writeback thread of all
+ * attached backing devices, in order to represent a rough
+ * time period, counter should be divided by dev_nr.
+ * Otherwise the idle time cannot be larger with more backing
+ * device attached.
+ * The following calculation equals to checking
+ * (counter / dev_nr) < (dev_nr * 6)
+ */
+ if (counter < (dev_nr * dev_nr * 6))
+ return false;
+
+ return true;
+}
+
+/*
+ * Idle_counter is increased every time when update_writeback_rate() is
+ * called. If all backing devices attached to the same cache set have
+ * identical dc->writeback_rate_update_seconds values, it is about 6
+ * rounds of update_writeback_rate() on each backing device before
+ * c->at_max_writeback_rate is set to 1, and then max wrteback rate set
+ * to each dc->writeback_rate.rate.
+ * In order to avoid extra locking cost for counting exact dirty cached
+ * devices number, c->attached_dev_nr is used to calculate the idle
+ * throushold. It might be bigger if not all cached device are in write-
+ * back mode, but it still works well with limited extra rounds of
+ * update_writeback_rate().
+ */
+static bool set_at_max_writeback_rate(struct cache_set *c,
+ struct cached_dev *dc)
+{
+ /* Don't sst max writeback rate if it is disabled */
+ if (!c->idle_max_writeback_rate_enabled)
+ return false;
+
+ /* Don't set max writeback rate if gc is running */
+ if (!c->gc_mark_valid)
+ return false;
+
+ if (!idle_counter_exceeded(c))
+ return false;
+
+ if (atomic_read(&c->at_max_writeback_rate) != 1)
+ atomic_set(&c->at_max_writeback_rate, 1);
+
+ atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
+
+ /* keep writeback_rate_target as existing value */
+ dc->writeback_rate_proportional = 0;
+ dc->writeback_rate_integral_scaled = 0;
+ dc->writeback_rate_change = 0;
+
+ /*
+ * In case new I/O arrives during before
+ * set_at_max_writeback_rate() returns.
+ */
+ if (!idle_counter_exceeded(c) ||
+ !atomic_read(&c->at_max_writeback_rate))
+ return false;
+
+ return true;
+}
+
+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);
+ struct cache_set *c = dc->disk.c;
+
+ /*
+ * should check BCACHE_DEV_RATE_DW_RUNNING before calling
+ * cancel_delayed_work_sync().
+ */
+ set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
+ /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
+ smp_mb__after_atomic();
+
+ /*
+ * CACHE_SET_IO_DISABLE might be set via sysfs interface,
+ * check it here too.
+ */
+ if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
+ test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
+ clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
+ /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
+ smp_mb__after_atomic();
+ return;
+ }
+
+ /*
+ * If the whole cache set is idle, set_at_max_writeback_rate()
+ * will set writeback rate to a max number. Then it is
+ * unncessary to update writeback rate for an idle cache set
+ * in maximum writeback rate number(s).
+ */
+ if (atomic_read(&dc->has_dirty) && dc->writeback_percent &&
+ !set_at_max_writeback_rate(c, dc)) {
+ do {
+ if (!down_read_trylock((&dc->writeback_lock))) {
+ dc->rate_update_retry++;
+ if (dc->rate_update_retry <=
+ BCH_WBRATE_UPDATE_MAX_SKIPS)
+ break;
+ down_read(&dc->writeback_lock);
+ dc->rate_update_retry = 0;
+ }
+ __update_writeback_rate(dc);
+ update_gc_after_writeback(c);
+ up_read(&dc->writeback_lock);
+ } while (0);
+ }
+
+
+ /*
+ * CACHE_SET_IO_DISABLE might be set via sysfs interface,
+ * check it here too.
+ */
+ if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
+ !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
+ schedule_delayed_work(&dc->writeback_rate_update,
+ dc->writeback_rate_update_seconds * HZ);
+ }
+
+ /*
+ * should check BCACHE_DEV_RATE_DW_RUNNING before calling
+ * cancel_delayed_work_sync().
+ */
+ clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
+ /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
+ smp_mb__after_atomic();
+}
+
+static unsigned int writeback_delay(struct cached_dev *dc,
+ unsigned int sectors)
+{
+ if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
+ !dc->writeback_percent)
+ return 0;
+
+ return bch_next_delay(&dc->writeback_rate, sectors);
+}
+
+struct dirty_io {
+ struct closure cl;
+ struct cached_dev *dc;
+ uint16_t sequence;
+ 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, NULL, bio->bi_inline_vecs,
+ DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), 0);
+ if (!io->dc->writeback_percent)
+ bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+
+ bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9;
+ bio->bi_private = w;
+ 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;
+
+ bio_free_pages(&io->bio);
+
+ /* This is kind of a dumb way of signalling errors. */
+ if (KEY_DIRTY(&w->key)) {
+ int ret;
+ unsigned int 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)
+{
+ struct keybuf_key *w = bio->bi_private;
+ struct dirty_io *io = w->private;
+
+ if (bio->bi_status) {
+ SET_KEY_DIRTY(&w->key, false);
+ bch_count_backing_io_errors(io->dc, bio);
+ }
+
+ 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;
+ struct cached_dev *dc = io->dc;
+
+ uint16_t next_sequence;
+
+ if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
+ /* Not our turn to write; wait for a write to complete */
+ closure_wait(&dc->writeback_ordering_wait, cl);
+
+ if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
+ /*
+ * Edge case-- it happened in indeterminate order
+ * relative to when we were added to wait list..
+ */
+ closure_wake_up(&dc->writeback_ordering_wait);
+ }
+
+ continue_at(cl, write_dirty, io->dc->writeback_write_wq);
+ return;
+ }
+
+ next_sequence = io->sequence + 1;
+
+ /*
+ * IO errors are signalled using the dirty bit on the key.
+ * If we failed to read, we should not attempt to write to the
+ * backing device. Instead, immediately go to write_dirty_finish
+ * to clean up.
+ */
+ if (KEY_DIRTY(&w->key)) {
+ dirty_init(w);
+ io->bio.bi_opf = REQ_OP_WRITE;
+ io->bio.bi_iter.bi_sector = KEY_START(&w->key);
+ bio_set_dev(&io->bio, io->dc->bdev);
+ io->bio.bi_end_io = dirty_endio;
+
+ /* I/O request sent to backing device */
+ closure_bio_submit(io->dc->disk.c, &io->bio, cl);
+ }
+
+ atomic_set(&dc->writeback_sequence_next, next_sequence);
+ closure_wake_up(&dc->writeback_ordering_wait);
+
+ continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
+}
+
+static void read_dirty_endio(struct bio *bio)
+{
+ struct keybuf_key *w = bio->bi_private;
+ struct dirty_io *io = w->private;
+
+ /* is_read = 1 */
+ bch_count_io_errors(io->dc->disk.c->cache,
+ bio->bi_status, 1,
+ "reading dirty data from cache");
+
+ dirty_endio(bio);
+}
+
+static void read_dirty_submit(struct closure *cl)
+{
+ struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+
+ closure_bio_submit(io->dc->disk.c, &io->bio, cl);
+
+ continue_at(cl, write_dirty, io->dc->writeback_write_wq);
+}
+
+static void read_dirty(struct cached_dev *dc)
+{
+ unsigned int delay = 0;
+ struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
+ size_t size;
+ int nk, i;
+ struct dirty_io *io;
+ struct closure cl;
+ uint16_t sequence = 0;
+
+ BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
+ atomic_set(&dc->writeback_sequence_next, sequence);
+ closure_init_stack(&cl);
+
+ /*
+ * XXX: if we error, background writeback just spins. Should use some
+ * mempools.
+ */
+
+ next = bch_keybuf_next(&dc->writeback_keys);
+
+ while (!kthread_should_stop() &&
+ !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
+ next) {
+ size = 0;
+ nk = 0;
+
+ do {
+ BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
+
+ /*
+ * Don't combine too many operations, even if they
+ * are all small.
+ */
+ if (nk >= MAX_WRITEBACKS_IN_PASS)
+ break;
+
+ /*
+ * If the current operation is very large, don't
+ * further combine operations.
+ */
+ if (size >= MAX_WRITESIZE_IN_PASS)
+ break;
+
+ /*
+ * Operations are only eligible to be combined
+ * if they are contiguous.
+ *
+ * TODO: add a heuristic willing to fire a
+ * certain amount of non-contiguous IO per pass,
+ * so that we can benefit from backing device
+ * command queueing.
+ */
+ if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
+ &START_KEY(&next->key)))
+ break;
+
+ size += KEY_SIZE(&next->key);
+ keys[nk++] = next;
+ } while ((next = bch_keybuf_next(&dc->writeback_keys)));
+
+ /* Now we have gathered a set of 1..5 keys to write back. */
+ for (i = 0; i < nk; i++) {
+ w = keys[i];
+
+ io = kzalloc(struct_size(io, bio.bi_inline_vecs,
+ DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)),
+ GFP_KERNEL);
+ if (!io)
+ goto err;
+
+ w->private = io;
+ io->dc = dc;
+ io->sequence = sequence++;
+
+ dirty_init(w);
+ io->bio.bi_opf = REQ_OP_READ;
+ io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
+ bio_set_dev(&io->bio, dc->disk.c->cache->bdev);
+ io->bio.bi_end_io = read_dirty_endio;
+
+ if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
+ goto err_free;
+
+ trace_bcache_writeback(&w->key);
+
+ down(&dc->in_flight);
+
+ /*
+ * We've acquired a semaphore for the maximum
+ * simultaneous number of writebacks; from here
+ * everything happens asynchronously.
+ */
+ closure_call(&io->cl, read_dirty_submit, NULL, &cl);
+ }
+
+ delay = writeback_delay(dc, size);
+
+ while (!kthread_should_stop() &&
+ !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
+ delay) {
+ schedule_timeout_interruptible(delay);
+ delay = writeback_delay(dc, 0);
+ }
+ }
+
+ 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 int inode,
+ uint64_t offset, int nr_sectors)
+{
+ struct bcache_device *d = c->devices[inode];
+ unsigned int stripe_offset, sectors_dirty;
+ int stripe;
+
+ if (!d)
+ return;
+
+ stripe = offset_to_stripe(d, offset);
+ if (stripe < 0)
+ return;
+
+ if (UUID_FLASH_ONLY(&c->uuids[inode]))
+ atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
+
+ stripe_offset = offset & (d->stripe_size - 1);
+
+ while (nr_sectors) {
+ int s = min_t(unsigned int, 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) {
+ if (!test_bit(stripe, d->full_dirty_stripes))
+ set_bit(stripe, d->full_dirty_stripes);
+ } else {
+ if (test_bit(stripe, d->full_dirty_stripes))
+ clear_bit(stripe, d->full_dirty_stripes);
+ }
+
+ nr_sectors -= s;
+ stripe_offset = 0;
+ stripe++;
+ }
+}
+
+static bool dirty_pred(struct keybuf *buf, struct bkey *k)
+{
+ struct cached_dev *dc = container_of(buf,
+ struct cached_dev,
+ writeback_keys);
+
+ BUG_ON(KEY_INODE(k) != dc->disk.id);
+
+ return KEY_DIRTY(k);
+}
+
+static void refill_full_stripes(struct cached_dev *dc)
+{
+ struct keybuf *buf = &dc->writeback_keys;
+ unsigned int start_stripe, next_stripe;
+ int stripe;
+ bool wrapped = false;
+
+ stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
+ if (stripe < 0)
+ 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;
+ }
+ }
+}
+
+/*
+ * Returns true if we scanned the entire disk
+ */
+static bool refill_dirty(struct cached_dev *dc)
+{
+ struct keybuf *buf = &dc->writeback_keys;
+ struct bkey start = KEY(dc->disk.id, 0, 0);
+ struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
+ struct bkey start_pos;
+
+ /*
+ * make sure keybuf pos is inside the range for this disk - at bringup
+ * we might not be attached yet so this disk's inode nr isn't
+ * initialized then
+ */
+ if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
+ bkey_cmp(&buf->last_scanned, &end) > 0)
+ buf->last_scanned = start;
+
+ if (dc->partial_stripes_expensive) {
+ refill_full_stripes(dc);
+ if (array_freelist_empty(&buf->freelist))
+ return false;
+ }
+
+ start_pos = buf->last_scanned;
+ bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
+
+ if (bkey_cmp(&buf->last_scanned, &end) < 0)
+ return false;
+
+ /*
+ * If we get to the end start scanning again from the beginning, and
+ * only scan up to where we initially started scanning from:
+ */
+ buf->last_scanned = start;
+ bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
+
+ return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
+}
+
+static int bch_writeback_thread(void *arg)
+{
+ struct cached_dev *dc = arg;
+ struct cache_set *c = dc->disk.c;
+ bool searched_full_index;
+
+ bch_ratelimit_reset(&dc->writeback_rate);
+
+ while (!kthread_should_stop() &&
+ !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
+ down_write(&dc->writeback_lock);
+ set_current_state(TASK_INTERRUPTIBLE);
+ /*
+ * If the bache device is detaching, skip here and continue
+ * to perform writeback. Otherwise, if no dirty data on cache,
+ * or there is dirty data on cache but writeback is disabled,
+ * the writeback thread should sleep here and wait for others
+ * to wake up it.
+ */
+ if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
+ (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
+ up_write(&dc->writeback_lock);
+
+ if (kthread_should_stop() ||
+ test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
+ set_current_state(TASK_RUNNING);
+ break;
+ }
+
+ schedule();
+ continue;
+ }
+ set_current_state(TASK_RUNNING);
+
+ searched_full_index = refill_dirty(dc);
+
+ if (searched_full_index &&
+ RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
+ atomic_set(&dc->has_dirty, 0);
+ SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
+ bch_write_bdev_super(dc, NULL);
+ /*
+ * If bcache device is detaching via sysfs interface,
+ * writeback thread should stop after there is no dirty
+ * data on cache. BCACHE_DEV_DETACHING flag is set in
+ * bch_cached_dev_detach().
+ */
+ if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+ struct closure cl;
+
+ closure_init_stack(&cl);
+ memset(&dc->sb.set_uuid, 0, 16);
+ SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
+
+ bch_write_bdev_super(dc, &cl);
+ closure_sync(&cl);
+
+ up_write(&dc->writeback_lock);
+ break;
+ }
+
+ /*
+ * When dirty data rate is high (e.g. 50%+), there might
+ * be heavy buckets fragmentation after writeback
+ * finished, which hurts following write performance.
+ * If users really care about write performance they
+ * may set BCH_ENABLE_AUTO_GC via sysfs, then when
+ * BCH_DO_AUTO_GC is set, garbage collection thread
+ * will be wake up here. After moving gc, the shrunk
+ * btree and discarded free buckets SSD space may be
+ * helpful for following write requests.
+ */
+ if (c->gc_after_writeback ==
+ (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) {
+ c->gc_after_writeback &= ~BCH_DO_AUTO_GC;
+ force_wake_up_gc(c);
+ }
+ }
+
+ up_write(&dc->writeback_lock);
+
+ read_dirty(dc);
+
+ if (searched_full_index) {
+ unsigned int delay = dc->writeback_delay * HZ;
+
+ while (delay &&
+ !kthread_should_stop() &&
+ !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
+ !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+ delay = schedule_timeout_interruptible(delay);
+
+ bch_ratelimit_reset(&dc->writeback_rate);
+ }
+ }
+
+ if (dc->writeback_write_wq)
+ destroy_workqueue(dc->writeback_write_wq);
+
+ cached_dev_put(dc);
+ wait_for_kthread_stop();
+
+ return 0;
+}
+
+/* Init */
+#define INIT_KEYS_EACH_TIME 500000
+
+struct sectors_dirty_init {
+ struct btree_op op;
+ unsigned int inode;
+ size_t count;
+};
+
+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));
+
+ op->count++;
+ if (!(op->count % INIT_KEYS_EACH_TIME))
+ cond_resched();
+
+ return MAP_CONTINUE;
+}
+
+static int bch_root_node_dirty_init(struct cache_set *c,
+ struct bcache_device *d,
+ struct bkey *k)
+{
+ struct sectors_dirty_init op;
+ int ret;
+
+ bch_btree_op_init(&op.op, -1);
+ op.inode = d->id;
+ op.count = 0;
+
+ ret = bcache_btree(map_keys_recurse,
+ k,
+ c->root,
+ &op.op,
+ &KEY(op.inode, 0, 0),
+ sectors_dirty_init_fn,
+ 0);
+ if (ret < 0)
+ pr_warn("sectors dirty init failed, ret=%d!\n", ret);
+
+ /*
+ * The op may be added to cache_set's btree_cache_wait
+ * in mca_cannibalize(), must ensure it is removed from
+ * the list and release btree_cache_alloc_lock before
+ * free op memory.
+ * Otherwise, the btree_cache_wait will be damaged.
+ */
+ bch_cannibalize_unlock(c);
+ finish_wait(&c->btree_cache_wait, &(&op.op)->wait);
+
+ return ret;
+}
+
+static int bch_dirty_init_thread(void *arg)
+{
+ struct dirty_init_thrd_info *info = arg;
+ struct bch_dirty_init_state *state = info->state;
+ struct cache_set *c = state->c;
+ struct btree_iter iter;
+ struct bkey *k, *p;
+ int cur_idx, prev_idx, skip_nr;
+
+ k = p = NULL;
+ prev_idx = 0;
+
+ bch_btree_iter_init(&c->root->keys, &iter, NULL);
+ k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
+ BUG_ON(!k);
+
+ p = k;
+
+ while (k) {
+ spin_lock(&state->idx_lock);
+ cur_idx = state->key_idx;
+ state->key_idx++;
+ spin_unlock(&state->idx_lock);
+
+ skip_nr = cur_idx - prev_idx;
+
+ while (skip_nr) {
+ k = bch_btree_iter_next_filter(&iter,
+ &c->root->keys,
+ bch_ptr_bad);
+ if (k)
+ p = k;
+ else {
+ atomic_set(&state->enough, 1);
+ /* Update state->enough earlier */
+ smp_mb__after_atomic();
+ goto out;
+ }
+ skip_nr--;
+ }
+
+ if (p) {
+ if (bch_root_node_dirty_init(c, state->d, p) < 0)
+ goto out;
+ }
+
+ p = NULL;
+ prev_idx = cur_idx;
+ }
+
+out:
+ /* In order to wake up state->wait in time */
+ smp_mb__before_atomic();
+ if (atomic_dec_and_test(&state->started))
+ wake_up(&state->wait);
+
+ return 0;
+}
+
+static int bch_btre_dirty_init_thread_nr(void)
+{
+ int n = num_online_cpus()/2;
+
+ if (n == 0)
+ n = 1;
+ else if (n > BCH_DIRTY_INIT_THRD_MAX)
+ n = BCH_DIRTY_INIT_THRD_MAX;
+
+ return n;
+}
+
+void bch_sectors_dirty_init(struct bcache_device *d)
+{
+ int i;
+ struct btree *b = NULL;
+ struct bkey *k = NULL;
+ struct btree_iter iter;
+ struct sectors_dirty_init op;
+ struct cache_set *c = d->c;
+ struct bch_dirty_init_state state;
+
+retry_lock:
+ b = c->root;
+ rw_lock(0, b, b->level);
+ if (b != c->root) {
+ rw_unlock(0, b);
+ goto retry_lock;
+ }
+
+ /* Just count root keys if no leaf node */
+ if (c->root->level == 0) {
+ bch_btree_op_init(&op.op, -1);
+ op.inode = d->id;
+ op.count = 0;
+
+ for_each_key_filter(&c->root->keys,
+ k, &iter, bch_ptr_invalid) {
+ if (KEY_INODE(k) != op.inode)
+ continue;
+ sectors_dirty_init_fn(&op.op, c->root, k);
+ }
+
+ rw_unlock(0, b);
+ return;
+ }
+
+ memset(&state, 0, sizeof(struct bch_dirty_init_state));
+ state.c = c;
+ state.d = d;
+ state.total_threads = bch_btre_dirty_init_thread_nr();
+ state.key_idx = 0;
+ spin_lock_init(&state.idx_lock);
+ atomic_set(&state.started, 0);
+ atomic_set(&state.enough, 0);
+ init_waitqueue_head(&state.wait);
+
+ for (i = 0; i < state.total_threads; i++) {
+ /* Fetch latest state.enough earlier */
+ smp_mb__before_atomic();
+ if (atomic_read(&state.enough))
+ break;
+
+ atomic_inc(&state.started);
+ state.infos[i].state = &state;
+ state.infos[i].thread =
+ kthread_run(bch_dirty_init_thread, &state.infos[i],
+ "bch_dirtcnt[%d]", i);
+ if (IS_ERR(state.infos[i].thread)) {
+ pr_err("fails to run thread bch_dirty_init[%d]\n", i);
+ atomic_dec(&state.started);
+ for (--i; i >= 0; i--)
+ kthread_stop(state.infos[i].thread);
+ goto out;
+ }
+ }
+
+out:
+ /* Must wait for all threads to stop. */
+ wait_event(state.wait, atomic_read(&state.started) == 0);
+ rw_unlock(0, b);
+}
+
+void 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 = false;
+ dc->writeback_consider_fragment = true;
+ dc->writeback_percent = 10;
+ dc->writeback_delay = 30;
+ atomic_long_set(&dc->writeback_rate.rate, 1024);
+ dc->writeback_rate_minimum = 8;
+
+ dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
+ dc->writeback_rate_p_term_inverse = 40;
+ dc->writeback_rate_fp_term_low = 1;
+ dc->writeback_rate_fp_term_mid = 10;
+ dc->writeback_rate_fp_term_high = 1000;
+ dc->writeback_rate_i_term_inverse = 10000;
+
+ /* For dc->writeback_lock contention in update_writeback_rate() */
+ dc->rate_update_retry = 0;
+
+ WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
+ INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
+}
+
+int bch_cached_dev_writeback_start(struct cached_dev *dc)
+{
+ dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
+ WQ_MEM_RECLAIM, 0);
+ if (!dc->writeback_write_wq)
+ return -ENOMEM;
+
+ cached_dev_get(dc);
+ dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
+ "bcache_writeback");
+ if (IS_ERR(dc->writeback_thread)) {
+ cached_dev_put(dc);
+ destroy_workqueue(dc->writeback_write_wq);
+ return PTR_ERR(dc->writeback_thread);
+ }
+ dc->writeback_running = true;
+
+ WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
+ schedule_delayed_work(&dc->writeback_rate_update,
+ dc->writeback_rate_update_seconds * HZ);
+
+ bch_writeback_queue(dc);
+
+ return 0;
+}