FAQ Search Today's Posts Mark Forums Read
» Video Reviews

» Linux Archive

Linux-archive is a website aiming to archive linux email lists and to make them easily accessible for linux users/developers.


» Sponsor

» Partners

» Sponsor


 
 
LinkBack Thread Tools
 
Old 05-10-2012, 03:11 AM
Kent Overstreet
 
Default bcache: Writeback

Signed-off-by: Kent Overstreet <koverstreet@google.com>
---
drivers/block/bcache/writeback.c | 518 ++++++++++++++++++++++++++++++++++++++
1 files changed, 518 insertions(+), 0 deletions(-)
create mode 100644 drivers/block/bcache/writeback.c

diff --git a/drivers/block/bcache/writeback.c b/drivers/block/bcache/writeback.c
new file mode 100644
index 0000000..cfcfe52
--- /dev/null
+++ b/drivers/block/bcache/writeback.c
@@ -0,0 +1,518 @@
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+
+static struct workqueue_struct *dirty_wq;
+
+static void read_dirty(struct cached_dev *);
+
+/* Background writeback */
+
+static void dirty_init(struct dirty *w)
+{
+ struct bio *bio = &w->io->bio;
+
+ bio_init(bio);
+ bio_get(bio);
+ if (!w->io->d->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_map(bio, NULL);
+}
+
+static int dirty_cmp(struct dirty *r, struct dirty *l)
+{
+ /* Overlapping keys must compare equal */
+ if (KEY_START(&r->key) >= l->key.key)
+ return 1;
+ if (KEY_START(&l->key) >= r->key.key)
+ return -1;
+ return 0;
+}
+
+static int btree_refill_dirty_leaf(struct btree *b, struct btree_op *op,
+ struct cached_dev *dc)
+{
+ struct dirty *w;
+ struct btree_iter iter;
+ btree_iter_init(b, &iter, &KEY(op->d->id, dc->last_found, 0));
+
+ /* To protect rb tree access vs. read_dirty() */
+ spin_lock(&dc->dirty_lock);
+
+ while (!array_freelist_empty(&dc->dirty_freelist)) {
+ struct bkey *k = btree_iter_next(&iter);
+ if (!k || KEY_DEV(k) != op->d->id)
+ break;
+
+ if (ptr_bad(b, k))
+ continue;
+
+ if (KEY_DIRTY(k)) {
+ w = array_alloc(&dc->dirty_freelist);
+
+ dc->last_found = k->key;
+ pr_debug("%s", pkey(k));
+ w->io = NULL;
+ bkey_copy(&w->key, k);
+ SET_KEY_DIRTY(&w->key, false);
+
+ if (RB_INSERT(&dc->dirty, w, node, dirty_cmp))
+ array_free(&dc->dirty_freelist, w);
+ }
+ }
+
+ spin_unlock(&dc->dirty_lock);
+
+ return 0;
+}
+
+static int btree_refill_dirty(struct btree *b, struct btree_op *op,
+ struct cached_dev *dc)
+{
+ int r;
+ struct btree_iter iter;
+ btree_iter_init(b, &iter, &KEY(op->d->id, dc->last_found, 0));
+
+ if (!b->level)
+ return btree_refill_dirty_leaf(b, op, dc);
+
+ while (!array_freelist_empty(&dc->dirty_freelist)) {
+ struct bkey *k = btree_iter_next(&iter);
+ if (!k)
+ break;
+
+ if (ptr_bad(b, k))
+ continue;
+
+ r = btree(refill_dirty, k, b, op, dc);
+ if (r) {
+ char buf[BDEVNAME_SIZE];
+ bdevname(dc->bdev, buf);
+
+ printk(KERN_WARNING "Error trying to read the btree "
+ "for background writeback on %s: "
+ "dirty data may have been lost!
", buf);
+ }
+
+ if (KEY_DEV(k) != op->d->id)
+ break;
+
+ cond_resched();
+ }
+
+ return 0;
+}
+
+static void refill_dirty(struct work_struct *work)
+{
+ struct cached_dev *dc = container_of(to_delayed_work(work),
+ struct cached_dev, refill_dirty);
+ uint64_t start;
+
+ struct btree_op op;
+ btree_op_init_stack(&op);
+ op.d = &dc->disk;
+
+ if (!atomic_read(&dc->disk.detaching) &&
+ !dc->writeback_running)
+ return;
+
+ down_write(&dc->writeback_lock);
+ start = dc->last_found;
+
+ if (!atomic_read(&dc->has_dirty)) {
+ SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
+ write_bdev_super(dc, NULL);
+ up_write(&dc->writeback_lock);
+ return;
+ }
+
+ btree_root(refill_dirty, dc->disk.c, &op, dc);
+ closure_sync(&op.cl);
+
+ pr_debug("found %s keys on %i from %llu to %llu, %i%% used",
+ RB_EMPTY_ROOT(&dc->dirty) ? "no" :
+ array_freelist_empty(&dc->dirty_freelist) ? "some" : "a few",
+ dc->disk.id, start, (uint64_t) dc->last_found,
+ dc->disk.c->gc_stats.in_use);
+
+ /* Got to the end of the btree */
+ if (!array_freelist_empty(&dc->dirty_freelist))
+ dc->last_found = 0;
+
+ /* Searched the entire btree - delay for awhile */
+ if (!array_freelist_empty(&dc->dirty_freelist) && !start)
+ queue_delayed_work(dirty_wq, &dc->refill_dirty,
+ dc->writeback_delay * HZ);
+
+ spin_lock(&dc->dirty_lock);
+
+ if (!RB_EMPTY_ROOT(&dc->dirty)) {
+ struct dirty *w;
+ w = RB_FIRST(&dc->dirty, struct dirty, node);
+ dc->writeback_start = KEY_START(&w->key);
+
+ w = RB_LAST(&dc->dirty, struct dirty, node);
+ dc->writeback_end = w->key.key;
+ } else {
+ dc->writeback_start = 0;
+ dc->writeback_end = 0;
+
+ if (!start) {
+ atomic_set(&dc->has_dirty, 0);
+ cached_dev_put(dc);
+ }
+ }
+
+ up_write(&dc->writeback_lock);
+
+ dc->next_writeback_io = local_clock();
+ read_dirty(dc);
+}
+
+bool bcache_in_writeback(struct cached_dev *dc, sector_t offset, unsigned len)
+{
+ struct dirty *w, s;
+ s.key = KEY(dc->disk.id, offset + len, len);
+
+ if (offset >= dc->writeback_end ||
+ offset + len <= dc->writeback_start)
+ return false;
+
+ spin_lock(&dc->dirty_lock);
+ w = RB_SEARCH(&dc->dirty, s, node, dirty_cmp);
+ if (w && !w->io) {
+ rb_erase(&w->node, &dc->dirty);
+ array_free(&dc->dirty_freelist, w);
+ w = NULL;
+ }
+
+ spin_unlock(&dc->dirty_lock);
+ return w != NULL;
+}
+
+void bcache_writeback_queue(struct cached_dev *d)
+{
+ queue_delayed_work(dirty_wq, &d->refill_dirty, 0);
+}
+
+void bcache_writeback_add(struct cached_dev *d, unsigned sectors)
+{
+ atomic_long_add(sectors, &d->disk.sectors_dirty);
+
+ if (!atomic_read(&d->has_dirty) &&
+ !atomic_xchg(&d->has_dirty, 1)) {
+ if (BDEV_STATE(&d->sb) != BDEV_STATE_DIRTY) {
+ SET_BDEV_STATE(&d->sb, BDEV_STATE_DIRTY);
+ /* XXX: should do this synchronously */
+ write_bdev_super(d, NULL);
+ }
+
+ atomic_inc(&d->count);
+ queue_delayed_work(dirty_wq, &d->refill_dirty,
+ d->writeback_delay * HZ);
+
+ if (d->writeback_percent)
+ schedule_delayed_work(&d->writeback_rate_update,
+ d->writeback_rate_update_seconds * HZ);
+ }
+}
+
+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 = atomic_long_read(&dc->disk.sectors_dirty);
+ 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 * 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->next_writeback_io + 10 * NSEC_PER_MSEC))
+ change = 0;
+
+ dc->writeback_rate = clamp_t(int64_t, dc->writeback_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)
+{
+ uint64_t now = local_clock();
+
+ if (atomic_read(&dc->disk.detaching) ||
+ !dc->writeback_percent)
+ return 0;
+
+ /* writeback_rate = sectors per 10 ms */
+ dc->next_writeback_io += div_u64(sectors * 10000000ULL,
+ dc->writeback_rate);
+
+ return time_after64(dc->next_writeback_io, now)
+ ? div_u64(dc->next_writeback_io - now, NSEC_PER_SEC / HZ)
+ : 0;
+}
+
+/* Background writeback - IO loop */
+
+static void write_dirty_finish(struct closure *cl)
+{
+ struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+ struct dirty *w = io->bio.bi_private;
+ struct cached_dev *dc = io->d;
+ struct bio_vec *bv = bio_iovec_idx(&io->bio, io->bio.bi_vcnt);
+
+ while (bv-- != w->io->bio.bi_io_vec)
+ __free_page(bv->bv_page);
+
+ closure_debug_destroy(cl);
+ kfree(io);
+
+ /* This is kind of a dumb way of signalling errors. */
+ if (!KEY_DIRTY(&w->key)) {
+ struct btree_op op;
+ btree_op_init_stack(&op);
+
+ op.type = BTREE_REPLACE;
+ bkey_copy(&op.replace, &w->key);
+ SET_KEY_DIRTY(&op.replace, true);
+
+ keylist_add(&op.keys, &w->key);
+
+ for (unsigned i = 0; i < KEY_PTRS(&w->key); i++)
+ atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
+
+ pr_debug("clearing %s", pkey(&w->key));
+ bcache_btree_insert(&op, dc->disk.c);
+ closure_sync(&op.cl);
+
+ atomic_long_inc(op.insert_collision
+ ? &dc->disk.c->writeback_keys_failed
+ : &dc->disk.c->writeback_keys_done);
+ }
+
+ spin_lock(&dc->dirty_lock);
+ rb_erase(&w->node, &dc->dirty);
+ array_free(&dc->dirty_freelist, w);
+ atomic_dec_bug(&dc->in_flight);
+
+ read_dirty(dc);
+}
+
+static void dirty_endio(struct bio *bio, int error)
+{
+ struct dirty *w = bio->bi_private;
+
+ if (error)
+ SET_KEY_DIRTY(&w->key, true);
+
+ bio_put(bio);
+ closure_put(&w->io->cl);
+}
+
+static void write_dirty(struct closure *cl)
+{
+ struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+ struct dirty *w = io->bio.bi_private;
+
+ dirty_init(w);
+ io->bio.bi_rw = WRITE|REQ_UNPLUG;
+ io->bio.bi_sector = KEY_START(&w->key);
+ io->bio.bi_bdev = io->d->bdev;
+ io->bio.bi_end_io = dirty_endio;
+
+ trace_bcache_write_dirty(&w->io->bio);
+ closure_bio_submit(&w->io->bio, cl, io->d->disk.bio_split);
+
+ continue_at(&io->cl, write_dirty_finish, dirty_wq);
+}
+
+static void read_dirty_endio(struct bio *bio, int error)
+{
+ struct dirty *w = bio->bi_private;
+
+ count_io_errors(PTR_CACHE(w->io->d->disk.c, &w->key, 0),
+ error, "reading dirty data from cache");
+
+ dirty_endio(bio, error);
+}
+
+static void read_dirty(struct cached_dev *dc)
+{
+ unsigned delay = writeback_delay(dc, 0);
+ struct dirty *w;
+ struct dirty_io *io;
+
+ /* XXX: if we error, background writeback could stall indefinitely */
+
+ while (1) {
+ w = RB_FIRST(&dc->dirty, struct dirty, node);
+
+ while (w && w->io)
+ w = RB_NEXT(w, node);
+
+ 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)) {
+ queue_delayed_work(dirty_wq, &dc->read_dirty, delay);
+ break;
+ }
+
+ dc->last_read = w->key.key;
+ w->io = ERR_PTR(-EINTR);
+ spin_unlock(&dc->dirty_lock);
+
+ 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->io = io;
+ w->io->d = dc;
+
+ dirty_init(w);
+ w->io->bio.bi_sector = PTR_OFFSET(&w->key, 0);
+ w->io->bio.bi_bdev = PTR_CACHE(dc->disk.c,
+ &w->key, 0)->bdev;
+ w->io->bio.bi_rw = READ|REQ_UNPLUG;
+ w->io->bio.bi_end_io = read_dirty_endio;
+
+ if (bio_alloc_pages(&w->io->bio, GFP_KERNEL))
+ goto err;
+
+ pr_debug("%s", pkey(&w->key));
+
+ closure_init(&w->io->cl, NULL);
+ set_closure_fn(&w->io->cl, write_dirty, dirty_wq);
+ closure_set_stopped(&w->io->cl);
+
+ trace_bcache_read_dirty(&w->io->bio);
+ closure_bio_submit_put(&w->io->bio, &w->io->cl,
+ dc->disk.bio_split);
+
+ delay = writeback_delay(dc, KEY_SIZE(&w->key));
+
+ if (atomic_inc_return(&dc->in_flight) >= 128)
+ return;
+
+ spin_lock(&dc->dirty_lock);
+ }
+
+ if (0) {
+err: spin_lock(&dc->dirty_lock);
+ if (!IS_ERR_OR_NULL(w->io))
+ kfree(w->io);
+ rb_erase(&w->node, &dc->dirty);
+ array_free(&dc->dirty_freelist, w);
+ }
+
+ if (RB_EMPTY_ROOT(&dc->dirty))
+ queue_delayed_work(dirty_wq, &dc->refill_dirty, 0);
+
+ spin_unlock(&dc->dirty_lock);
+}
+
+static void read_dirty_work(struct work_struct *work)
+{
+ struct cached_dev *dc = container_of(to_delayed_work(work),
+ struct cached_dev, read_dirty);
+
+ spin_lock(&dc->dirty_lock);
+ read_dirty(dc);
+}
+
+void bcache_writeback_init_cached_dev(struct cached_dev *d)
+{
+ INIT_DELAYED_WORK(&d->refill_dirty, refill_dirty);
+ INIT_DELAYED_WORK(&d->read_dirty, read_dirty_work);
+ init_rwsem(&d->writeback_lock);
+ array_allocator_init(&d->dirty_freelist);
+
+ d->dirty = RB_ROOT;
+ d->writeback_metadata = true;
+ d->writeback_running = true;
+ d->writeback_delay = 30;
+ d->writeback_rate = 1024;
+
+ d->writeback_rate_update_seconds = 30;
+ d->writeback_rate_d_term = 16;
+ d->writeback_rate_p_term_inverse = 64;
+ d->writeback_rate_d_smooth = 8;
+
+ INIT_DELAYED_WORK(&d->writeback_rate_update, update_writeback_rate);
+ schedule_delayed_work(&d->writeback_rate_update,
+ d->writeback_rate_update_seconds * HZ);
+}
+
+void bcache_writeback_exit(void)
+{
+ if (dirty_wq)
+ destroy_workqueue(dirty_wq);
+}
+
+int __init bcache_writeback_init(void)
+{
+ dirty_wq = create_singlethread_workqueue("bcache_writeback");
+ if (!dirty_wq)
+ return -ENOMEM;
+
+ return 0;
+}
--
1.7.9.rc2

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel
 

Thread Tools




All times are GMT. The time now is 08:36 PM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.
Copyright 2007 - 2008, www.linux-archive.org