bcache: Convert writeback to a kthread
This simplifies the writeback flow control quite a bit - previously, it
was conceptually two coroutines, refill_dirty() and read_dirty(). This
makes the code quite a bit more straightforward.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 09410eb..674e2f4 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -509,7 +509,7 @@
/* Limit number of writeback bios in flight */
struct semaphore in_flight;
- struct closure_with_timer writeback;
+ struct task_struct *writeback_thread;
struct keybuf writeback_keys;
@@ -1038,7 +1038,11 @@
#define KEY_START(k) (KEY_OFFSET(k) - KEY_SIZE(k))
#define START_KEY(k) KEY(KEY_INODE(k), KEY_START(k), 0)
-#define MAX_KEY KEY(~(~0 << 20), ((uint64_t) ~0) >> 1, 0)
+
+#define MAX_KEY_INODE (~(~0 << 20))
+#define MAX_KEY_OFFSET (((uint64_t) ~0) >> 1)
+#define MAX_KEY KEY(MAX_KEY_INODE, MAX_KEY_OFFSET, 0)
+
#define ZERO_KEY KEY(0, 0, 0)
/*
@@ -1214,8 +1218,6 @@
void bch_debug_exit(void);
int bch_debug_init(struct kobject *);
-void bch_writeback_exit(void);
-int bch_writeback_init(void);
void bch_request_exit(void);
int bch_request_init(void);
void bch_btree_exit(void);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f89e229..b79dd5a 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1029,6 +1029,7 @@
struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
cancel_delayed_work_sync(&dc->writeback_rate_update);
+ kthread_stop(dc->writeback_thread);
mutex_lock(&bch_register_lock);
@@ -2006,7 +2007,6 @@
static void bcache_exit(void)
{
bch_debug_exit();
- bch_writeback_exit();
bch_request_exit();
bch_btree_exit();
if (bcache_kobj)
@@ -2039,7 +2039,6 @@
sysfs_create_files(bcache_kobj, files) ||
bch_btree_init() ||
bch_request_init() ||
- bch_writeback_init() ||
bch_debug_init(bcache_kobj))
goto err;
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 51dc709..4392f3f 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -11,18 +11,11 @@
#include "debug.h"
#include "writeback.h"
+#include <linux/delay.h>
+#include <linux/freezer.h>
+#include <linux/kthread.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)
@@ -72,9 +65,6 @@
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)
@@ -90,6 +80,9 @@
__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)
@@ -105,37 +98,11 @@
return min_t(uint64_t, ret, HZ);
}
-/* 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 = KEY_START(k);
- unsigned nr_sectors = KEY_SIZE(k);
- struct cached_dev *dc = container_of(buf, struct cached_dev,
- writeback_keys);
-
- if (!KEY_DIRTY(k))
- return false;
-
- do_div(stripe, dc->disk.stripe_size);
-
- while (1) {
- if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) ==
- dc->disk.stripe_size)
- return true;
-
- if (nr_sectors <= dc->disk.stripe_size)
- return false;
-
- nr_sectors -= dc->disk.stripe_size;
- stripe++;
- }
-}
+struct dirty_io {
+ struct closure cl;
+ struct cached_dev *dc;
+ struct bio bio;
+};
static void dirty_init(struct keybuf_key *w)
{
@@ -153,132 +120,6 @@
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) ==
- dc->disk.stripe_size)
- goto full_stripes;
-
- goto normal_refill;
-full_stripes:
- searched_from_start = false; /* not searching entire btree */
- 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);
-
- bch_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_offset;
- uint64_t stripe = offset;
-
- if (!d)
- return;
-
- do_div(stripe, d->stripe_size);
-
- 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;
-
- 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);
@@ -378,30 +219,33 @@
continue_at(cl, write_dirty, system_wq);
}
-static void read_dirty(struct closure *cl)
+static void read_dirty(struct cached_dev *dc)
{
- struct cached_dev *dc = container_of(cl, struct cached_dev,
- writeback.cl);
- unsigned delay = writeback_delay(dc, 0);
+ 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 (1) {
+ 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 (delay > 0 &&
- (KEY_START(&w->key) != dc->last_read ||
- jiffies_to_msecs(delay) > 50))
- delay = schedule_timeout_uninterruptible(delay);
+ 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);
@@ -427,7 +271,7 @@
trace_bcache_writeback(&w->key);
down(&dc->in_flight);
- closure_call(&io->cl, read_dirty_submit, NULL, cl);
+ closure_call(&io->cl, read_dirty_submit, NULL, &cl);
delay = writeback_delay(dc, KEY_SIZE(&w->key));
}
@@ -443,7 +287,148 @@
* Wait for outstanding writeback IOs to finish (and keybuf slots to be
* freed) before refilling again
*/
- continue_at(cl, refill_dirty, dirty_wq);
+ 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;
+ uint64_t stripe = offset;
+
+ if (!d)
+ return;
+
+ do_div(stripe, d->stripe_size);
+
+ 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;
+
+ atomic_add(s, d->stripe_sectors_dirty + stripe);
+ nr_sectors -= s;
+ stripe_offset = 0;
+ stripe++;
+ }
+}
+
+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 = KEY_START(k);
+ unsigned nr_sectors = KEY_SIZE(k);
+ struct cached_dev *dc = container_of(buf, struct cached_dev,
+ writeback_keys);
+
+ if (!KEY_DIRTY(k))
+ return false;
+
+ do_div(stripe, dc->disk.stripe_size);
+
+ while (1) {
+ if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) ==
+ dc->disk.stripe_size)
+ return true;
+
+ if (nr_sectors <= dc->disk.stripe_size)
+ return false;
+
+ nr_sectors -= dc->disk.stripe_size;
+ stripe++;
+ }
+}
+
+static bool refill_dirty(struct cached_dev *dc)
+{
+ struct keybuf *buf = &dc->writeback_keys;
+ bool searched_from_start = false;
+ struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
+
+ 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) ==
+ dc->disk.stripe_size)
+ goto full_stripes;
+
+ goto normal_refill;
+full_stripes:
+ searched_from_start = false; /* not searching entire btree */
+ 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);
+ }
+
+ 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) ||
+ (!atomic_read(&dc->disk.detaching) &&
+ !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() &&
+ !atomic_read(&dc->disk.detaching))
+ delay = schedule_timeout_interruptible(delay);
+ }
+ }
+
+ return 0;
}
/* Init */
@@ -483,12 +468,10 @@
btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
}
-void bch_cached_dev_writeback_init(struct cached_dev *dc)
+int bch_cached_dev_writeback_init(struct cached_dev *dc)
{
sema_init(&dc->in_flight, 64);
- closure_init_unlocked(&dc->writeback);
init_rwsem(&dc->writeback_lock);
-
bch_keybuf_init(&dc->writeback_keys);
dc->writeback_metadata = true;
@@ -502,22 +485,16 @@
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);
-}
-
-void bch_writeback_exit(void)
-{
- if (dirty_wq)
- destroy_workqueue(dirty_wq);
-}
-
-int __init bch_writeback_init(void)
-{
- dirty_wq = create_workqueue("bcache_writeback");
- if (!dirty_wq)
- return -ENOMEM;
return 0;
}
diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
index 3496188..60516bf 100644
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -56,11 +56,30 @@
in_use <= CUTOFF_WRITEBACK;
}
+static inline void bch_writeback_queue(struct cached_dev *dc)
+{
+ wake_up_process(dc->writeback_thread);
+}
+
+static inline 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);
+ }
+}
+
void bcache_dev_sectors_dirty_add(struct cache_set *, unsigned, uint64_t, int);
-void bch_writeback_queue(struct cached_dev *);
-void bch_writeback_add(struct cached_dev *);
void bch_sectors_dirty_init(struct cached_dev *dc);
-void bch_cached_dev_writeback_init(struct cached_dev *);
+int bch_cached_dev_writeback_init(struct cached_dev *);
#endif