/* * 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/freezer.h>#include <linux/kthread.h>#include <trace/events/bcache.h> /* 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 */ 	int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);	int64_t derivative = dirty - dc->disk.sectors_dirty_last;	int64_t proportional = dirty - target;	int64_t change; 	dc->disk.sectors_dirty_last = dirty; 	/* Scale to sectors per second */ 	proportional *= dc->writeback_rate_update_seconds;	proportional = div_s64(proportional, dc->writeback_rate_p_term_inverse); 	derivative = div_s64(derivative, dc->writeback_rate_update_seconds); 	derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,			      (dc->writeback_rate_d_term /			       dc->writeback_rate_update_seconds) ?: 1, 0); 	derivative *= dc->writeback_rate_d_term;	derivative = div_s64(derivative, dc->writeback_rate_p_term_inverse); 	change = proportional + derivative; 	/* Don't increase writeback rate if the device isn't keeping up */	if (change > 0 &&	    time_after64(local_clock(),			 dc->writeback_rate.next + NSEC_PER_MSEC))		change = 0; 	dc->writeback_rate.rate =		clamp_t(int64_t, (int64_t) dc->writeback_rate.rate + change,			1, NSEC_PER_MSEC); 	dc->writeback_rate_proportional = proportional;	dc->writeback_rate_derivative = derivative;	dc->writeback_rate_change = change;	dc->writeback_rate_target = target;} 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); 	schedule_delayed_work(&dc->writeback_rate_update,			      dc->writeback_rate_update_seconds * HZ);} static unsigned writeback_delay(struct cached_dev *dc, unsigned 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;	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);	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 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)) {		int ret;		unsigned 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, 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, system_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, system_wq);} static void read_dirty(struct cached_dev *dc){	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 (!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 (KEY_START(&w->key) != dc->last_read ||		    jiffies_to_msecs(delay) > 50)			while (!kthread_should_stop() && delay)				delay = schedule_timeout_uninterruptible(delay); 		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); 		down(&dc->in_flight);		closure_call(&io->cl, read_dirty_submit, NULL, &cl); 		delay = writeback_delay(dc, KEY_SIZE(&w->key));	} 	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 inode,				  uint64_t offset, int nr_sectors){	struct bcache_device *d = c->devices[inode];	unsigned stripe_offset, stripe, sectors_dirty; 	if (!d)		return; 	stripe = offset_to_stripe(d, offset);	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; 		if (stripe >= d->nr_stripes)			return; 		sectors_dirty = atomic_add_return(s,					d->stripe_sectors_dirty + stripe);		if (sectors_dirty == d->stripe_size)			set_bit(stripe, d->full_dirty_stripes);		else			clear_bit(stripe, d->full_dirty_stripes); 		nr_sectors -= s;		stripe_offset = 0;		stripe++;	}} static bool dirty_pred(struct keybuf *buf, struct bkey *k){	return KEY_DIRTY(k);} static void refill_full_stripes(struct cached_dev *dc){	struct keybuf *buf = &dc->writeback_keys;	unsigned start_stripe, stripe, next_stripe;	bool wrapped = false; 	stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned)); 	if (stripe >= dc->disk.nr_stripes)		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;		}	}} static bool refill_dirty(struct cached_dev *dc){	struct keybuf *buf = &dc->writeback_keys;	struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);	bool searched_from_start = false; 	if (dc->partial_stripes_expensive) {		refill_full_stripes(dc);		if (array_freelist_empty(&buf->freelist))			return false;	} 	if (bkey_cmp(&buf->last_scanned, &end) >= 0) {		buf->last_scanned = KEY(dc->disk.id, 0, 0);		searched_from_start = true;	} 	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) ||		    (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&		     !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() &&			       !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))				delay = schedule_timeout_uninterruptible(delay);		}	} 	return 0;} /* Init */ struct sectors_dirty_init {	struct btree_op	op;	unsigned	inode;}; 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)); 	return MAP_CONTINUE;} void bch_sectors_dirty_init(struct cached_dev *dc){	struct sectors_dirty_init op; 	bch_btree_op_init(&op.op, -1);	op.inode = dc->disk.id; 	bch_btree_map_keys(&op.op, dc->disk.c, &KEY(op.inode, 0, 0),			   sectors_dirty_init_fn, 0); 	dc->disk.sectors_dirty_last = bcache_dev_sectors_dirty(&dc->disk);} int 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		= true;	dc->writeback_percent		= 10;	dc->writeback_delay		= 30;	dc->writeback_rate.rate		= 1024; 	dc->writeback_rate_update_seconds = 5;	dc->writeback_rate_d_term	= 30;	dc->writeback_rate_p_term_inverse = 6000; 	dc->writeback_thread = kthread_create(bch_writeback_thread, dc,					      "bcache_writeback");	if (IS_ERR(dc->writeback_thread))		return PTR_ERR(dc->writeback_thread);

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