bcache: A block layer cache

Does writethrough and writeback caching, handles unclean shutdown, and
has a bunch of other nifty features motivated by real world usage.

See the wiki at http://bcache.evilpiepirate.org for more.

Signed-off-by: Kent Overstreet <koverstreet@google.com>

1 files changed, 254 insertions, 0 deletions

diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
new file mode 100644
index 0000000..c69fc92
--- /dev/null
+++ b/drivers/md/bcache/movinggc.c
@@ -0,0 +1,254 @@
+/*
+ * Moving/copying garbage collector
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+struct moving_io {
+	struct keybuf_key	*w;
+	struct search		s;
+	struct bbio		bio;
+};
+
+static bool moving_pred(struct keybuf *buf, struct bkey *k)
+{
+	struct cache_set *c = container_of(buf, struct cache_set,
+					   moving_gc_keys);
+	unsigned i;
+
+	for (i = 0; i < KEY_PTRS(k); i++) {
+		struct cache *ca = PTR_CACHE(c, k, i);
+		struct bucket *g = PTR_BUCKET(c, k, i);
+
+		if (GC_SECTORS_USED(g) < ca->gc_move_threshold)
+			return true;
+	}
+
+	return false;
+}
+
+/* Moving GC - IO loop */
+
+static void moving_io_destructor(struct closure *cl)
+{
+	struct moving_io *io = container_of(cl, struct moving_io, s.cl);
+	kfree(io);
+}
+
+static void write_moving_finish(struct closure *cl)
+{
+	struct moving_io *io = container_of(cl, struct moving_io, s.cl);
+	struct bio *bio = &io->bio.bio;
+	struct bio_vec *bv = bio_iovec_idx(bio, bio->bi_vcnt);
+
+	while (bv-- != bio->bi_io_vec)
+		__free_page(bv->bv_page);
+
+	pr_debug("%s %s", io->s.op.insert_collision
+		 ? "collision moving" : "moved",
+		 pkey(&io->w->key));
+
+	bch_keybuf_del(&io->s.op.c->moving_gc_keys, io->w);
+
+	atomic_dec_bug(&io->s.op.c->in_flight);
+	closure_wake_up(&io->s.op.c->moving_gc_wait);
+
+	closure_return_with_destructor(cl, moving_io_destructor);
+}
+
+static void read_moving_endio(struct bio *bio, int error)
+{
+	struct moving_io *io = container_of(bio->bi_private,
+					    struct moving_io, s.cl);
+
+	if (error)
+		io->s.error = error;
+
+	bch_bbio_endio(io->s.op.c, bio, error, "reading data to move");
+}
+
+static void moving_init(struct moving_io *io)
+{
+	struct bio *bio = &io->bio.bio;
+
+	bio_init(bio);
+	bio_get(bio);
+	bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+
+	bio->bi_size		= KEY_SIZE(&io->w->key) << 9;
+	bio->bi_max_vecs	= DIV_ROUND_UP(KEY_SIZE(&io->w->key),
+					       PAGE_SECTORS);
+	bio->bi_private		= &io->s.cl;
+	bio->bi_io_vec		= bio->bi_inline_vecs;
+	bio_map(bio, NULL);
+}
+
+static void write_moving(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct moving_io *io = container_of(s, struct moving_io, s);
+
+	if (!s->error) {
+		trace_bcache_write_moving(&io->bio.bio);
+
+		moving_init(io);
+
+		io->bio.bio.bi_sector	= KEY_START(&io->w->key);
+		s->op.lock		= -1;
+		s->op.write_prio	= 1;
+		s->op.cache_bio		= &io->bio.bio;
+
+		s->writeback		= KEY_DIRTY(&io->w->key);
+		s->op.csum		= KEY_CSUM(&io->w->key);
+
+		s->op.type = BTREE_REPLACE;
+		bkey_copy(&s->op.replace, &io->w->key);
+
+		closure_init(&s->op.cl, cl);
+		bch_insert_data(&s->op.cl);
+	}
+
+	continue_at(cl, write_moving_finish, NULL);
+}
+
+static void read_moving_submit(struct closure *cl)
+{
+	struct search *s = container_of(cl, struct search, cl);
+	struct moving_io *io = container_of(s, struct moving_io, s);
+	struct bio *bio = &io->bio.bio;
+
+	trace_bcache_read_moving(bio);
+	bch_submit_bbio(bio, s->op.c, &io->w->key, 0);
+
+	continue_at(cl, write_moving, bch_gc_wq);
+}
+
+static void read_moving(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, moving_gc);
+	struct keybuf_key *w;
+	struct moving_io *io;
+	struct bio *bio;
+
+	/* XXX: if we error, background writeback could stall indefinitely */
+
+	while (!test_bit(CACHE_SET_STOPPING, &c->flags)) {
+		w = bch_keybuf_next_rescan(c, &c->moving_gc_keys, &MAX_KEY);
+		if (!w)
+			break;
+
+		io = kzalloc(sizeof(struct moving_io) + sizeof(struct bio_vec)
+			     * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
+			     GFP_KERNEL);
+		if (!io)
+			goto err;
+
+		w->private	= io;
+		io->w		= w;
+		io->s.op.inode	= KEY_INODE(&w->key);
+		io->s.op.c	= c;
+
+		moving_init(io);
+		bio = &io->bio.bio;
+
+		bio->bi_rw	= READ;
+		bio->bi_end_io	= read_moving_endio;
+
+		if (bio_alloc_pages(bio, GFP_KERNEL))
+			goto err;
+
+		pr_debug("%s", pkey(&w->key));
+
+		closure_call(&io->s.cl, read_moving_submit, NULL, &c->gc.cl);
+
+		if (atomic_inc_return(&c->in_flight) >= 64) {
+			closure_wait_event(&c->moving_gc_wait, cl,
+					   atomic_read(&c->in_flight) < 64);
+			continue_at(cl, read_moving, bch_gc_wq);
+		}
+	}
+
+	if (0) {
+err:		if (!IS_ERR_OR_NULL(w->private))
+			kfree(w->private);
+
+		bch_keybuf_del(&c->moving_gc_keys, w);
+	}
+
+	closure_return(cl);
+}
+
+void bch_moving_gc(struct closure *cl)
+{
+	struct cache_set *c = container_of(cl, struct cache_set, gc.cl);
+	struct cache *ca;
+	struct bucket *b;
+	unsigned i;
+
+	bool bucket_cmp(struct bucket *l, struct bucket *r)
+	{
+		return GC_SECTORS_USED(l) < GC_SECTORS_USED(r);
+	}
+
+	unsigned top(struct cache *ca)
+	{
+		return GC_SECTORS_USED(heap_peek(&ca->heap));
+	}
+
+	if (!c->copy_gc_enabled)
+		closure_return(cl);
+
+	mutex_lock(&c->bucket_lock);
+
+	for_each_cache(ca, c, i) {
+		unsigned sectors_to_move = 0;
+		unsigned reserve_sectors = ca->sb.bucket_size *
+			min(fifo_used(&ca->free), ca->free.size / 2);
+
+		ca->heap.used = 0;
+
+		for_each_bucket(b, ca) {
+			if (!GC_SECTORS_USED(b))
+				continue;
+
+			if (!heap_full(&ca->heap)) {
+				sectors_to_move += GC_SECTORS_USED(b);
+				heap_add(&ca->heap, b, bucket_cmp);
+			} else if (bucket_cmp(b, heap_peek(&ca->heap))) {
+				sectors_to_move -= top(ca);
+				sectors_to_move += GC_SECTORS_USED(b);
+
+				ca->heap.data[0] = b;
+				heap_sift(&ca->heap, 0, bucket_cmp);
+			}
+		}
+
+		while (sectors_to_move > reserve_sectors) {
+			heap_pop(&ca->heap, b, bucket_cmp);
+			sectors_to_move -= GC_SECTORS_USED(b);
+		}
+
+		ca->gc_move_threshold = top(ca);
+
+		pr_debug("threshold %u", ca->gc_move_threshold);
+	}
+
+	mutex_unlock(&c->bucket_lock);
+
+	c->moving_gc_keys.last_scanned = ZERO_KEY;
+
+	closure_init(&c->moving_gc, cl);
+	read_moving(&c->moving_gc);
+
+	closure_return(cl);
+}
+
+void bch_moving_init_cache_set(struct cache_set *c)
+{
+	bch_keybuf_init(&c->moving_gc_keys, moving_pred);
+}