Commit 84f0db03 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcache: Refactor request_write() 



Try to improve some of the naming a bit to be more consistent, and also
improve the flow of control in request_write() a bit.

Signed-off-by: default avatarKent Overstreet <kmo@daterainc.com>
parent c2f95ae2

drivers/md/bcache/btree.h

+1 −1
Original line number Diff line number Diff line
@@ -260,7 +260,7 @@ struct btree_op { 
	} type:8;



	unsigned		csum:1;

	unsigned		skip:1;

	unsigned		bypass:1;

	unsigned		flush_journal:1;



	unsigned		insert_data_done:1;

drivers/md/bcache/request.c

+182 −186
Original line number Diff line number Diff line
@@ -25,8 +25,6 @@ 


struct kmem_cache *bch_search_cache;



static void check_should_skip(struct cached_dev *, struct search *);



/* Cgroup interface */



#ifdef CONFIG_CGROUP_BCACHE
@@ -480,7 +478,7 @@ static void bch_insert_data_loop(struct closure *cl) 
	struct search *s = container_of(op, struct search, op);

	struct bio *bio = op->cache_bio, *n;



	if (op->skip)

	if (op->bypass)

		return bio_invalidate(cl);



	if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0) {
@@ -557,7 +555,7 @@ err: 
		 * we wait for buckets to be freed up, so just invalidate the

		 * rest of the write.

		 */

		op->skip = true;

		op->bypass = true;

		return bio_invalidate(cl);

	} else {

		/*
@@ -590,8 +588,8 @@ err: 
 * It inserts the data in op->cache_bio; bi_sector is used for the key offset,

 * and op->inode is used for the key inode.

 *

 * If op->skip is true, instead of inserting the data it invalidates the region

 * of the cache represented by op->cache_bio and op->inode.

 * If op->bypass is true, instead of inserting the data it invalidates the

 * region of the cache represented by op->cache_bio and op->inode.

 */

void bch_insert_data(struct closure *cl)

{
@@ -717,7 +715,6 @@ static struct search *search_alloc(struct bio *bio, struct bcache_device *d) 
	s->orig_bio		= bio;

	s->write		= (bio->bi_rw & REQ_WRITE) != 0;

	s->op.flush_journal	= (bio->bi_rw & (REQ_FLUSH|REQ_FUA)) != 0;

	s->op.skip		= (bio->bi_rw & REQ_DISCARD) != 0;

	s->recoverable		= 1;

	s->start_time		= jiffies;

	do_bio_hook(s);
@@ -757,6 +754,134 @@ static void cached_dev_bio_complete(struct closure *cl) 
	cached_dev_put(dc);

}



unsigned bch_get_congested(struct cache_set *c)

{

	int i;

	long rand;



	if (!c->congested_read_threshold_us &&

	    !c->congested_write_threshold_us)

		return 0;



	i = (local_clock_us() - c->congested_last_us) / 1024;

	if (i < 0)

		return 0;



	i += atomic_read(&c->congested);

	if (i >= 0)

		return 0;



	i += CONGESTED_MAX;



	if (i > 0)

		i = fract_exp_two(i, 6);



	rand = get_random_int();

	i -= bitmap_weight(&rand, BITS_PER_LONG);



	return i > 0 ? i : 1;

}



static void add_sequential(struct task_struct *t)

{

	ewma_add(t->sequential_io_avg,

		 t->sequential_io, 8, 0);



	t->sequential_io = 0;

}



static struct hlist_head *iohash(struct cached_dev *dc, uint64_t k)

{

	return &dc->io_hash[hash_64(k, RECENT_IO_BITS)];

}



static bool check_should_bypass(struct cached_dev *dc, struct search *s)

{

	struct cache_set *c = s->op.c;

	struct bio *bio = &s->bio.bio;

	unsigned mode = cache_mode(dc, bio);

	unsigned sectors, congested = bch_get_congested(c);



	if (atomic_read(&dc->disk.detaching) ||

	    c->gc_stats.in_use > CUTOFF_CACHE_ADD ||

	    (bio->bi_rw & REQ_DISCARD))

		goto skip;



	if (mode == CACHE_MODE_NONE ||

	    (mode == CACHE_MODE_WRITEAROUND &&

	     (bio->bi_rw & REQ_WRITE)))

		goto skip;



	if (bio->bi_sector & (c->sb.block_size - 1) ||

	    bio_sectors(bio) & (c->sb.block_size - 1)) {

		pr_debug("skipping unaligned io");

		goto skip;

	}



	if (!congested && !dc->sequential_cutoff)

		goto rescale;



	if (!congested &&

	    mode == CACHE_MODE_WRITEBACK &&

	    (bio->bi_rw & REQ_WRITE) &&

	    (bio->bi_rw & REQ_SYNC))

		goto rescale;



	if (dc->sequential_merge) {

		struct io *i;



		spin_lock(&dc->io_lock);



		hlist_for_each_entry(i, iohash(dc, bio->bi_sector), hash)

			if (i->last == bio->bi_sector &&

			    time_before(jiffies, i->jiffies))

				goto found;



		i = list_first_entry(&dc->io_lru, struct io, lru);



		add_sequential(s->task);

		i->sequential = 0;

found:

		if (i->sequential + bio->bi_size > i->sequential)

			i->sequential	+= bio->bi_size;



		i->last			 = bio_end_sector(bio);

		i->jiffies		 = jiffies + msecs_to_jiffies(5000);

		s->task->sequential_io	 = i->sequential;



		hlist_del(&i->hash);

		hlist_add_head(&i->hash, iohash(dc, i->last));

		list_move_tail(&i->lru, &dc->io_lru);



		spin_unlock(&dc->io_lock);

	} else {

		s->task->sequential_io = bio->bi_size;



		add_sequential(s->task);

	}



	sectors = max(s->task->sequential_io,

		      s->task->sequential_io_avg) >> 9;



	if (dc->sequential_cutoff &&

	    sectors >= dc->sequential_cutoff >> 9) {

		trace_bcache_bypass_sequential(s->orig_bio);

		goto skip;

	}



	if (congested && sectors >= congested) {

		trace_bcache_bypass_congested(s->orig_bio);

		goto skip;

	}



rescale:

	bch_rescale_priorities(c, bio_sectors(bio));

	return false;

skip:

	bch_mark_sectors_bypassed(s, bio_sectors(bio));

	return true;

}



/* Process reads */



static void cached_dev_read_complete(struct closure *cl)
@@ -854,8 +979,8 @@ static void request_read_done_bh(struct closure *cl) 
	struct search *s = container_of(cl, struct search, cl);

	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);



	bch_mark_cache_accounting(s, !s->cache_miss, s->op.skip);

	trace_bcache_read(s->orig_bio, !s->cache_miss, s->op.skip);

	bch_mark_cache_accounting(s, !s->cache_miss, s->op.bypass);

	trace_bcache_read(s->orig_bio, !s->cache_miss, s->op.bypass);



	if (s->error)

		continue_at_nobarrier(cl, request_read_error, bcache_wq);
@@ -873,7 +998,7 @@ static int cached_dev_cache_miss(struct btree *b, struct search *s, 
	struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);

	struct bio *miss;



	if (s->cache_miss || s->op.skip) {

	if (s->cache_miss || s->op.bypass) {

		miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);

		if (miss == bio)

			s->op.lookup_done = true;
@@ -940,9 +1065,7 @@ static void request_read(struct cached_dev *dc, struct search *s) 
{

	struct closure *cl = &s->cl;



	check_should_skip(dc, s);

	closure_call(&s->op.cl, btree_read_async, NULL, cl);



	continue_at(cl, request_read_done_bh, NULL);

}
@@ -961,41 +1084,48 @@ static void request_write(struct cached_dev *dc, struct search *s) 
{

	struct closure *cl = &s->cl;

	struct bio *bio = &s->bio.bio;

	struct bkey start, end;

	start = KEY(dc->disk.id, bio->bi_sector, 0);

	end = KEY(dc->disk.id, bio_end_sector(bio), 0);

	struct bkey start = KEY(dc->disk.id, bio->bi_sector, 0);

	struct bkey end = KEY(dc->disk.id, bio_end_sector(bio), 0);



	bch_keybuf_check_overlapping(&s->op.c->moving_gc_keys, &start, &end);



	check_should_skip(dc, s);

	down_read_non_owner(&dc->writeback_lock);



	if (bch_keybuf_check_overlapping(&dc->writeback_keys, &start, &end)) {

		s->op.skip	= false;

		/*

		 * We overlap with some dirty data undergoing background

		 * writeback, force this write to writeback

		 */

		s->op.bypass	= false;

		s->writeback	= true;

	}



	/*

	 * Discards aren't _required_ to do anything, so skipping if

	 * check_overlapping returned true is ok

	 *

	 * But check_overlapping drops dirty keys for which io hasn't started,

	 * so we still want to call it.

	 */

	if (bio->bi_rw & REQ_DISCARD)

		goto skip;

		s->op.bypass = true;



	if (should_writeback(dc, s->orig_bio,

			     cache_mode(dc, bio),

			     s->op.skip)) {

		s->op.skip = false;

			     s->op.bypass)) {

		s->op.bypass = false;

		s->writeback = true;

	}



	if (s->op.skip)

		goto skip;



	trace_bcache_write(s->orig_bio, s->writeback, s->op.skip);

	trace_bcache_write(s->orig_bio, s->writeback, s->op.bypass);



	if (!s->writeback) {

		s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,

						   dc->disk.bio_split);

	if (s->op.bypass) {

		s->op.cache_bio = s->orig_bio;

		bio_get(s->op.cache_bio);



		if (!(bio->bi_rw & REQ_DISCARD) ||

		    blk_queue_discard(bdev_get_queue(dc->bdev)))

			closure_bio_submit(bio, cl, s->d);

	} else {

	} else if (s->writeback) {

		bch_writeback_add(dc);

		s->op.cache_bio = bio;
@@ -1011,21 +1141,15 @@ static void request_write(struct cached_dev *dc, struct search *s) 


			closure_bio_submit(flush, cl, s->d);

		}

	} else {

		s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,

						   dc->disk.bio_split);



		closure_bio_submit(bio, cl, s->d);

	}

out:



	closure_call(&s->op.cl, bch_insert_data, NULL, cl);

	continue_at(cl, cached_dev_write_complete, NULL);

skip:

	s->op.skip = true;

	s->op.cache_bio = s->orig_bio;

	bio_get(s->op.cache_bio);



	if ((bio->bi_rw & REQ_DISCARD) &&

	    !blk_queue_discard(bdev_get_queue(dc->bdev)))

		goto out;



	closure_bio_submit(bio, cl, s->d);

	goto out;

}



static void request_nodata(struct cached_dev *dc, struct search *s)
@@ -1033,14 +1157,10 @@ static void request_nodata(struct cached_dev *dc, struct search *s) 
	struct closure *cl = &s->cl;

	struct bio *bio = &s->bio.bio;



	if (bio->bi_rw & REQ_DISCARD) {

		request_write(dc, s);

		return;

	}



	if (s->op.flush_journal)

		bch_journal_meta(s->op.c, cl);



	/* If it's a flush, we send the flush to the backing device too */

	closure_bio_submit(bio, cl, s->d);



	continue_at(cl, cached_dev_bio_complete, NULL);
@@ -1048,134 +1168,6 @@ static void request_nodata(struct cached_dev *dc, struct search *s) 


/* Cached devices - read & write stuff */



unsigned bch_get_congested(struct cache_set *c)

{

	int i;

	long rand;



	if (!c->congested_read_threshold_us &&

	    !c->congested_write_threshold_us)

		return 0;



	i = (local_clock_us() - c->congested_last_us) / 1024;

	if (i < 0)

		return 0;



	i += atomic_read(&c->congested);

	if (i >= 0)

		return 0;



	i += CONGESTED_MAX;



	if (i > 0)

		i = fract_exp_two(i, 6);



	rand = get_random_int();

	i -= bitmap_weight(&rand, BITS_PER_LONG);



	return i > 0 ? i : 1;

}



static void add_sequential(struct task_struct *t)

{

	ewma_add(t->sequential_io_avg,

		 t->sequential_io, 8, 0);



	t->sequential_io = 0;

}



static struct hlist_head *iohash(struct cached_dev *dc, uint64_t k)

{

	return &dc->io_hash[hash_64(k, RECENT_IO_BITS)];

}



static void check_should_skip(struct cached_dev *dc, struct search *s)

{

	struct cache_set *c = s->op.c;

	struct bio *bio = &s->bio.bio;

	unsigned mode = cache_mode(dc, bio);

	unsigned sectors, congested = bch_get_congested(c);



	if (atomic_read(&dc->disk.detaching) ||

	    c->gc_stats.in_use > CUTOFF_CACHE_ADD ||

	    (bio->bi_rw & REQ_DISCARD))

		goto skip;



	if (mode == CACHE_MODE_NONE ||

	    (mode == CACHE_MODE_WRITEAROUND &&

	     (bio->bi_rw & REQ_WRITE)))

		goto skip;



	if (bio->bi_sector   & (c->sb.block_size - 1) ||

	    bio_sectors(bio) & (c->sb.block_size - 1)) {

		pr_debug("skipping unaligned io");

		goto skip;

	}



	if (!congested && !dc->sequential_cutoff)

		goto rescale;



	if (!congested &&

	    mode == CACHE_MODE_WRITEBACK &&

	    (bio->bi_rw & REQ_WRITE) &&

	    (bio->bi_rw & REQ_SYNC))

		goto rescale;



	if (dc->sequential_merge) {

		struct io *i;



		spin_lock(&dc->io_lock);



		hlist_for_each_entry(i, iohash(dc, bio->bi_sector), hash)

			if (i->last == bio->bi_sector &&

			    time_before(jiffies, i->jiffies))

				goto found;



		i = list_first_entry(&dc->io_lru, struct io, lru);



		add_sequential(s->task);

		i->sequential = 0;

found:

		if (i->sequential + bio->bi_size > i->sequential)

			i->sequential	+= bio->bi_size;



		i->last			 = bio_end_sector(bio);

		i->jiffies		 = jiffies + msecs_to_jiffies(5000);

		s->task->sequential_io	 = i->sequential;



		hlist_del(&i->hash);

		hlist_add_head(&i->hash, iohash(dc, i->last));

		list_move_tail(&i->lru, &dc->io_lru);



		spin_unlock(&dc->io_lock);

	} else {

		s->task->sequential_io = bio->bi_size;



		add_sequential(s->task);

	}



	sectors = max(s->task->sequential_io,

		      s->task->sequential_io_avg) >> 9;



	if (dc->sequential_cutoff &&

	    sectors >= dc->sequential_cutoff >> 9) {

		trace_bcache_bypass_sequential(s->orig_bio);

		goto skip;

	}



	if (congested && sectors >= congested) {

		trace_bcache_bypass_congested(s->orig_bio);

		goto skip;

	}



rescale:

	bch_rescale_priorities(c, bio_sectors(bio));

	return;

skip:

	bch_mark_sectors_bypassed(s, bio_sectors(bio));

	s->op.skip = true;

}



static void cached_dev_make_request(struct request_queue *q, struct bio *bio)

{

	struct search *s;
@@ -1195,12 +1187,16 @@ static void cached_dev_make_request(struct request_queue *q, struct bio *bio) 
		s = search_alloc(bio, d);

		trace_bcache_request_start(s, bio);



		if (!bio_has_data(bio))

		if (!bio->bi_size)

			request_nodata(dc, s);

		else if (rw)

		else {

			s->op.bypass = check_should_bypass(dc, s);



			if (rw)

				request_write(dc, s);

			else

				request_read(dc, s);

		}

	} else {

		if ((bio->bi_rw & REQ_DISCARD) &&

		    !blk_queue_discard(bdev_get_queue(dc->bdev)))
@@ -1298,21 +1294,21 @@ static void flash_dev_make_request(struct request_queue *q, struct bio *bio) 


	trace_bcache_request_start(s, bio);



	if (bio_has_data(bio) && !rw) {

		closure_call(&s->op.cl, btree_read_async, NULL, cl);

	} else if (bio_has_data(bio) || s->op.skip) {

	if (!bio->bi_size) {

		if (s->op.flush_journal)

			bch_journal_meta(s->op.c, cl);

	} else if (rw) {

		bch_keybuf_check_overlapping(&s->op.c->moving_gc_keys,

					&KEY(d->id, bio->bi_sector, 0),

					&KEY(d->id, bio_end_sector(bio), 0));



		s->op.bypass	= (bio->bi_rw & REQ_DISCARD) != 0;

		s->writeback	= true;

		s->op.cache_bio	= bio;



		closure_call(&s->op.cl, bch_insert_data, NULL, cl);

	} else {

		/* No data - probably a cache flush */

		if (s->op.flush_journal)

			bch_journal_meta(s->op.c, cl);

		closure_call(&s->op.cl, btree_read_async, NULL, cl);

	}



	continue_at(cl, search_free, NULL);

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