bcachefs: Btree key cache

This introduces a new kind of btree iterator, cached iterators, which
point to keys cached in a hash table. The cache also acts as a write
cache - in the update path, we journal the update but defer updating the
btree until the cached entry is flushed by journal reclaim.

Cache coherency is for now up to the users to handle, which isn't ideal
but should be good enough for now.

These new iterators will be used for updating inodes and alloc info (the
alloc and stripes btrees).

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

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/bcachefs/btree_key_cache.h b/fs/bcachefs/btree_key_cache.h
new file mode 100644
index 000000000000..fbc29336091f
--- /dev/null
+++ b/fs/bcachefs/btree_key_cache.h
@@ -0,0 +1,23 @@
+#ifndef _BCACHEFS_BTREE_KEY_CACHE_H
+#define _BCACHEFS_BTREE_KEY_CACHE_H
+
+int bch2_btree_iter_traverse_cached(struct btree_iter *);
+
+bool bch2_btree_insert_key_cached(struct btree_trans *,
+			struct btree_iter *, struct bkey_i *);
+int bch2_btree_key_cache_flush(struct btree_trans *,
+			       enum btree_id, struct bpos);
+#ifdef CONFIG_BCACHEFS_DEBUG
+void bch2_btree_key_cache_verify_clean(struct btree_trans *,
+				enum btree_id, struct bpos);
+#else
+static inline void
+bch2_btree_key_cache_verify_clean(struct btree_trans *trans,
+				enum btree_id id, struct bpos pos) {}
+#endif
+
+void bch2_fs_btree_key_cache_exit(struct btree_key_cache *);
+void bch2_fs_btree_key_cache_init_early(struct btree_key_cache *);
+int bch2_fs_btree_key_cache_init(struct btree_key_cache *);
+
+#endif /* _BCACHEFS_BTREE_KEY_CACHE_H */