Commit 9e5c3535 authored by Slava Pestov's avatar Slava Pestov Committed by Kent Overstreet
Browse files

bcache: fix uninterruptible sleep in writeback thread 



There were two issues here:

- writeback thread did not start until the device first became dirty
- writeback thread used uninterruptible sleep once running

Without this patch I see kernel warnings printed and a load average of
1.52 after booting my test VM. With this patch the warnings are gone and
the load average is near 0.00 as expected.

Signed-off-by: default avatarKent Overstreet <kmo@daterainc.com>
parent c5aa4a31

drivers/md/bcache/super.c

+3 −0
Original line number Diff line number Diff line
@@ -1042,6 +1042,9 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) 
	 */

	atomic_set(&dc->count, 1);



	if (bch_cached_dev_writeback_start(dc))

		return -ENOMEM;



	if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {

		bch_sectors_dirty_init(dc);

		atomic_set(&dc->has_dirty, 1);

drivers/md/bcache/writeback.c

+10 −4
Original line number Diff line number Diff line
@@ -239,7 +239,7 @@ static void read_dirty(struct cached_dev *dc) 
		if (KEY_START(&w->key) != dc->last_read ||

		    jiffies_to_msecs(delay) > 50)

			while (!kthread_should_stop() && delay)

				delay = schedule_timeout_uninterruptible(delay);

				delay = schedule_timeout_interruptible(delay);



		dc->last_read	= KEY_OFFSET(&w->key);
@@ -436,7 +436,7 @@ static int bch_writeback_thread(void *arg) 
			while (delay &&

			       !kthread_should_stop() &&

			       !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))

				delay = schedule_timeout_uninterruptible(delay);

				delay = schedule_timeout_interruptible(delay);

		}

	}
@@ -478,7 +478,7 @@ void bch_sectors_dirty_init(struct cached_dev *dc) 
	dc->disk.sectors_dirty_last = bcache_dev_sectors_dirty(&dc->disk);

}



int bch_cached_dev_writeback_init(struct cached_dev *dc)

void bch_cached_dev_writeback_init(struct cached_dev *dc)

{

	sema_init(&dc->in_flight, 64);

	init_rwsem(&dc->writeback_lock);
@@ -494,14 +494,20 @@ int bch_cached_dev_writeback_init(struct cached_dev *dc) 
	dc->writeback_rate_d_term	= 30;

	dc->writeback_rate_p_term_inverse = 6000;



	INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);

}



int bch_cached_dev_writeback_start(struct cached_dev *dc)

{

	dc->writeback_thread = kthread_create(bch_writeback_thread, dc,

					      "bcache_writeback");

	if (IS_ERR(dc->writeback_thread))

		return PTR_ERR(dc->writeback_thread);



	INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);

	schedule_delayed_work(&dc->writeback_rate_update,

			      dc->writeback_rate_update_seconds * HZ);



	bch_writeback_queue(dc);



	return 0;

}

drivers/md/bcache/writeback.h

+2 −1
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ static inline void bch_writeback_add(struct cached_dev *dc) 
void bcache_dev_sectors_dirty_add(struct cache_set *, unsigned, uint64_t, int);



void bch_sectors_dirty_init(struct cached_dev *dc);

int bch_cached_dev_writeback_init(struct cached_dev *);

void bch_cached_dev_writeback_init(struct cached_dev *);

int bch_cached_dev_writeback_start(struct cached_dev *);



#endif

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