bcachefs: LRU btree

This implements new persistent LRUs, to be used for buckets containing
cached data, as well as stripes ordered by time when a block became
empty.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 119 insertions, 0 deletions

diff --git a/fs/bcachefs/lru.c b/fs/bcachefs/lru.c
new file mode 100644
index 000000000000..2ababca5efe5
--- /dev/null
+++ b/fs/bcachefs/lru.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "btree_iter.h"
+#include "btree_update.h"
+#include "error.h"
+#include "lru.h"
+
+const char *bch2_lru_invalid(const struct bch_fs *c, struct bkey_s_c k)
+{
+	const struct bch_lru *lru = bkey_s_c_to_lru(k).v;
+
+	if (bkey_val_bytes(k.k) < sizeof(*lru))
+		return "incorrect value size";
+
+	return NULL;
+}
+
+void bch2_lru_to_text(struct printbuf *out, struct bch_fs *c,
+		      struct bkey_s_c k)
+{
+	const struct bch_lru *lru = bkey_s_c_to_lru(k).v;
+
+	pr_buf(out, "idx %llu", le64_to_cpu(lru->idx));
+}
+
+static int lru_delete(struct btree_trans *trans, u64 id, u64 idx, u64 time)
+{
+	struct bch_fs *c = trans->c;
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	u64 existing_idx;
+	int ret = 0;
+
+	if (!time)
+		return 0;
+
+	bch2_trans_iter_init(trans, &iter, BTREE_ID_lru,
+			     POS(id, time),
+			     BTREE_ITER_INTENT|
+			     BTREE_ITER_WITH_UPDATES);
+	k = bch2_btree_iter_peek_slot(&iter);
+	ret = bkey_err(k);
+	if (ret)
+		goto err;
+
+	if (k.k->type != KEY_TYPE_lru) {
+		bch2_fs_inconsistent(c,
+			"pointer to nonexistent lru %llu:%llu",
+			id, time);
+		ret = -EIO;
+		goto err;
+	}
+
+	existing_idx = le64_to_cpu(bkey_s_c_to_lru(k).v->idx);
+	if (existing_idx != idx) {
+		bch2_fs_inconsistent(c,
+			"lru %llu:%llu with wrong backpointer: got %llu, should be %llu",
+			id, time, existing_idx, idx);
+		ret = -EIO;
+		goto err;
+	}
+
+	ret = bch2_btree_delete_at(trans, &iter, 0);
+err:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+static int lru_set(struct btree_trans *trans, u64 lru_id, u64 idx, u64 *time)
+{
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	struct bkey_i_lru *lru;
+	int ret = 0;
+
+	if (!*time)
+		return 0;
+
+	for_each_btree_key_norestart(trans, iter, BTREE_ID_lru,
+			POS(lru_id, *time),
+			BTREE_ITER_SLOTS|
+			BTREE_ITER_INTENT|
+			BTREE_ITER_WITH_UPDATES, k, ret)
+		if (bkey_deleted(k.k))
+			break;
+
+	if (ret)
+		goto err;
+
+	BUG_ON(iter.pos.inode != lru_id);
+	*time = iter.pos.offset;
+
+	lru = bch2_trans_kmalloc(trans, sizeof(*lru));
+	ret = PTR_ERR_OR_ZERO(lru);
+	if (ret)
+		goto err;
+
+	bkey_lru_init(&lru->k_i);
+	lru->k.p	= iter.pos;
+	lru->v.idx	= cpu_to_le64(idx);
+
+	ret = bch2_trans_update(trans, &iter, &lru->k_i, 0);
+	if (ret)
+		goto err;
+err:
+	bch2_trans_iter_exit(trans, &iter);
+	return ret;
+}
+
+int bch2_lru_change(struct btree_trans *trans, u64 id, u64 idx,
+		    u64 old_time, u64 *new_time)
+{
+	if (old_time == *new_time)
+		return 0;
+
+	return  lru_delete(trans, id, idx, old_time) ?:
+		lru_set(trans, id, idx, new_time);
+}