bcachefs: New data structure for buckets waiting on journal commit

Implement a hash table, using cuckoo hashing, for empty buckets that are
waiting on a journal commit before they can be reused.

This replaces the journal_seq field of bucket_mark, and is part of
eventually getting rid of the in memory bucket array.

We may need to make bch2_bucket_needs_journal_commit() lockless, pending
profiling and testing.

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

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/bcachefs/buckets_waiting_for_journal_types.h b/fs/bcachefs/buckets_waiting_for_journal_types.h
new file mode 100644
index 000000000000..e593db061d81
--- /dev/null
+++ b/fs/bcachefs/buckets_waiting_for_journal_types.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BUCKETS_WAITING_FOR_JOURNAL_TYPES_H
+#define _BUCKETS_WAITING_FOR_JOURNAL_TYPES_H
+
+#include <linux/siphash.h>
+
+struct bucket_hashed {
+	u64			dev_bucket;
+	u64			journal_seq;
+};
+
+struct buckets_waiting_for_journal_table {
+	unsigned		bits;
+	u64			hash_seeds[3];
+	struct bucket_hashed	d[];
+};
+
+struct buckets_waiting_for_journal {
+	struct mutex		lock;
+	struct buckets_waiting_for_journal_table *t;
+};
+
+#endif /* _BUCKETS_WAITING_FOR_JOURNAL_TYPES_H */